diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-devices-system-cpu | 10 | ||||
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 28 | ||||
| -rw-r--r-- | Documentation/powerpc/elfnote.rst | 41 | ||||
| -rw-r--r-- | Documentation/powerpc/firmware-assisted-dump.rst | 220 | ||||
| -rw-r--r-- | Documentation/powerpc/index.rst | 2 | ||||
| -rw-r--r-- | Documentation/powerpc/ultravisor.rst | 1054 |
6 files changed, 1275 insertions, 80 deletions
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu index 5f7d7b14fa44..06d0931119cc 100644 --- a/Documentation/ABI/testing/sysfs-devices-system-cpu +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu @@ -562,3 +562,13 @@ Description: Umwait control or C0.2 state. The time is an unsigned 32-bit number. Note that a value of zero means there is no limit. Low order two bits must be zero. + +What: /sys/devices/system/cpu/svm +Date: August 2019 +Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> + Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org> +Description: Secure Virtual Machine + + If 1, it means the system is using the Protected Execution + Facility in POWER9 and newer processors. i.e., it is a Secure + Virtual Machine. diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 782e9072407b..d3814789304f 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -860,6 +860,10 @@ disable_radix [PPC] Disable RADIX MMU mode on POWER9 + disable_tlbie [PPC] + Disable TLBIE instruction. Currently does not work + with KVM, with HASH MMU, or with coherent accelerators. + disable_cpu_apicid= [X86,APIC,SMP] Format: <int> The number of initial APIC ID for the @@ -4641,6 +4645,11 @@ /sys/power/pm_test). Only available when CONFIG_PM_DEBUG is set. Default value is 5. + svm= [PPC] + Format: { on | off | y | n | 1 | 0 } + This parameter controls use of the Protected + Execution Facility on pSeries. + swapaccount=[0|1] [KNL] Enable accounting of swap in memory resource controller if no parameter or 1 is given or disable @@ -5326,3 +5335,22 @@ A hex value specifying bitmask with supplemental xhci host controller quirks. Meaning of each bit can be consulted in header drivers/usb/host/xhci.h. + + xmon [PPC] + Format: { early | on | rw | ro | off } + Controls if xmon debugger is enabled. Default is off. + Passing only "xmon" is equivalent to "xmon=early". + early Call xmon as early as possible on boot; xmon + debugger is called from setup_arch(). + on xmon debugger hooks will be installed so xmon + is only called on a kernel crash. Default mode, + i.e. either "ro" or "rw" mode, is controlled + with CONFIG_XMON_DEFAULT_RO_MODE. + rw xmon debugger hooks will be installed so xmon + is called only on a kernel crash, mode is write, + meaning SPR registers, memory and, other data + can be written using xmon commands. + ro same as "rw" option above but SPR registers, + memory, and other data can't be written using + xmon commands. + off xmon is disabled. diff --git a/Documentation/powerpc/elfnote.rst b/Documentation/powerpc/elfnote.rst new file mode 100644 index 000000000000..06602248621c --- /dev/null +++ b/Documentation/powerpc/elfnote.rst @@ -0,0 +1,41 @@ +========================== +ELF Note PowerPC Namespace +========================== + +The PowerPC namespace in an ELF Note of the kernel binary is used to store +capabilities and information which can be used by a bootloader or userland. + +Types and Descriptors +--------------------- + +The types to be used with the "PowerPC" namesapce are defined in [#f1]_. + + 1) PPC_ELFNOTE_CAPABILITIES + +Define the capabilities supported/required by the kernel. This type uses a +bitmap as "descriptor" field. Each bit is described below: + +- Ultravisor-capable bit (PowerNV only). + +.. code-block:: c + + #define PPCCAP_ULTRAVISOR_BIT (1 << 0) + +Indicate that the powerpc kernel binary knows how to run in an +ultravisor-enabled system. + +In an ultravisor-enabled system, some machine resources are now controlled +by the ultravisor. If the kernel is not ultravisor-capable, but it ends up +being run on a machine with ultravisor, the kernel will probably crash +trying to access ultravisor resources. For instance, it may crash in early +boot trying to set the partition table entry 0. + +In an ultravisor-enabled system, a bootloader could warn the user or prevent +the kernel from being run if the PowerPC ultravisor capability doesn't exist +or the Ultravisor-capable bit is not set. + +References +---------- + +.. [#f1] arch/powerpc/include/asm/elfnote.h + diff --git a/Documentation/powerpc/firmware-assisted-dump.rst b/Documentation/powerpc/firmware-assisted-dump.rst index 9ca12830a48e..0455a78486d5 100644 --- a/Documentation/powerpc/firmware-assisted-dump.rst +++ b/Documentation/powerpc/firmware-assisted-dump.rst @@ -9,18 +9,18 @@ a crashed system, and to do so from a fully-reset system, and to minimize the total elapsed time until the system is back in production use. -- Firmware assisted dump (fadump) infrastructure is intended to replace +- Firmware-Assisted Dump (FADump) infrastructure is intended to replace the existing phyp assisted dump. - Fadump uses the same firmware interfaces and memory reservation model as phyp assisted dump. -- Unlike phyp dump, fadump exports the memory dump through /proc/vmcore +- Unlike phyp dump, FADump exports the memory dump through /proc/vmcore in the ELF format in the same way as kdump. This helps us reuse the kdump infrastructure for dump capture and filtering. - Unlike phyp dump, userspace tool does not need to refer any sysfs interface while reading /proc/vmcore. -- Unlike phyp dump, fadump allows user to release all the memory reserved +- Unlike phyp dump, FADump allows user to release all the memory reserved for dump, with a single operation of echo 1 > /sys/kernel/fadump_release_mem. -- Once enabled through kernel boot parameter, fadump can be +- Once enabled through kernel boot parameter, FADump can be started/stopped through /sys/kernel/fadump_registered interface (see sysfs files section below) and can be easily integrated with kdump service start/stop init scripts. @@ -34,7 +34,7 @@ dump offers several strong, practical advantages: in a clean, consistent state. - Once the dump is copied out, the memory that held the dump is immediately available to the running kernel. And therefore, - unlike kdump, fadump doesn't need a 2nd reboot to get back + unlike kdump, FADump doesn't need a 2nd reboot to get back the system to the production configuration. The above can only be accomplished by coordination with, @@ -46,10 +46,9 @@ as follows: These registered sections of memory are reserved by the first kernel during early boot. -- When a system crashes, the Power firmware will save - the low memory (boot memory of size larger of 5% of system RAM - or 256MB) of RAM to the previous registered region. It will - also save system registers, and hardware PTE's. +- When system crashes, the Power firmware will copy the registered + low memory regions (boot memory) from source to destination area. + It will also save hardware PTE's. NOTE: The term 'boot memory' means size of the low memory chunk @@ -61,9 +60,9 @@ as follows: the default calculated size. Use this option if default boot memory size is not sufficient for second kernel to boot successfully. For syntax of crashkernel= parameter, - refer to Documentation/admin-guide/kdump/kdump.rst. If any offset is - provided in crashkernel= parameter, it will be ignored - as fadump uses a predefined offset to reserve memory + refer to Documentation/admin-guide/kdump/kdump.rst. If any + offset is provided in crashkernel= parameter, it will be + ignored as FADump uses a predefined offset to reserve memory for boot memory dump preservation in case of a crash. - After the low memory (boot memory) area has been saved, the @@ -71,13 +70,15 @@ as follows: *not* clear the RAM. It will then launch the bootloader, as normal. -- The freshly booted kernel will notice that there is a new - node (ibm,dump-kernel) in the device tree, indicating that +- The freshly booted kernel will notice that there is a new node + (rtas/ibm,kernel-dump on pSeries or ibm,opal/dump/mpipl-boot + on OPAL platform) in the device tree, indicating that there is crash data available from a previous boot. During the early boot OS will reserve rest of the memory above boot memory size effectively booting with restricted memory - size. This will make sure that the second kernel will not - touch any of the dump memory area. + size. This will make sure that this kernel (also, referred + to as second kernel or capture kernel) will not touch any + of the dump memory area. - User-space tools will read /proc/vmcore to obtain the contents of memory, which holds the previous crashed kernel dump in ELF @@ -94,8 +95,30 @@ as follows: # echo 1 > /sys/kernel/fadump_release_mem Please note that the firmware-assisted dump feature -is only available on Power6 and above systems with recent -firmware versions. +is only available on POWER6 and above systems on pSeries +(PowerVM) platform and POWER9 and above systems with OP940 +or later firmware versions on PowerNV (OPAL) platform. +Note that, OPAL firmware exports ibm,opal/dump node when +FADump is supported on PowerNV platform. + +On OPAL based machines, system first boots into an intermittent +kernel (referred to as petitboot kernel) before booting into the +capture kernel. This kernel would have minimal kernel and/or +userspace support to process crash data. Such kernel needs to +preserve previously crash'ed kernel's memory for the subsequent +capture kernel boot to process this crash data. Kernel config +option CONFIG_PRESERVE_FA_DUMP has to be enabled on such kernel +to ensure that crash data is preserved to process later. + +-- On OPAL based machines (PowerNV), if the kernel is build with + CONFIG_OPAL_CORE=y, OPAL memory at the time of crash is also + exported as /sys/firmware/opal/core file. This procfs file is + helpful in debugging OPAL crashes with GDB. The kernel memory + used for exporting this procfs file can be released by echo'ing + '1' to /sys/kernel/fadump_release_opalcore node. + + e.g. + # echo 1 > /sys/kernel/fadump_release_opalcore Implementation details: ----------------------- @@ -110,72 +133,95 @@ that are run. If there is dump data, then the /sys/kernel/fadump_release_mem file is created, and the reserved memory is held. -If there is no waiting dump data, then only the memory required -to hold CPU state, HPTE region, boot memory dump and elfcore -header, is usually reserved at an offset greater than boot memory -size (see Fig. 1). This area is *not* released: this region will -be kept permanently reserved, so that it can act as a receptacle -for a copy of the boot memory content in addition to CPU state -and HPTE region, in the case a crash does occur. Since this reserved -memory area is used only after the system crash, there is no point in -blocking this significant chunk of memory from production kernel. -Hence, the implementation uses the Linux kernel's Contiguous Memory -Allocator (CMA) for memory reservation if CMA is configured for kernel. -With CMA reservation this memory will be available for applications to -use it, while kernel is prevented from using it. With this fadump will -still be able to capture all of the kernel memory and most of the user -space memory except the user pages that were present in CMA region:: +If there is no waiting dump data, then only the memory required to +hold CPU state, HPTE region, boot memory dump, FADump header and +elfcore header, is usually reserved at an offset greater than boot +memory size (see Fig. 1). This area is *not* released: this region +will be kept permanently reserved, so that it can act as a receptacle +for a copy of the boot memory content in addition to CPU state and +HPTE region, in the case a crash does occur. + +Since this reserved memory area is used only after the system crash, +there is no point in blocking this significant chunk of memory from +production kernel. Hence, the implementation uses the Linux kernel's +Contiguous Memory Allocator (CMA) for memory reservation if CMA is +configured for kernel. With CMA reservation this memory will be +available for applications to use it, while kernel is prevented from +using it. With this FADump will still be able to capture all of the +kernel memory and most of the user space memory except the user pages +that were present in CMA region:: o Memory Reservation during first kernel - Low memory Top of memory - 0 boot memory size | - | | |<--Reserved dump area -->| | - V V | Permanent Reservation | V - +-----------+----------/ /---+---+----+-----------+----+------+ - | | |CPU|HPTE| DUMP |ELF | | - +-----------+----------/ /---+---+----+-----------+----+------+ - | ^ - | | - \ / - ------------------------------------------- - Boot memory content gets transferred to - reserved area by firmware at the time of - crash + Low memory Top of memory + 0 boot memory size |<--- Reserved dump area --->| | + | | | Permanent Reservation | | + V V | | V + +-----------+-----/ /---+---+----+-------+-----+-----+----+--+ + | | |///|////| DUMP | HDR | ELF |////| | + +-----------+-----/ /---+---+----+-------+-----+-----+----+--+ + | ^ ^ ^ ^ ^ + | | | | | | + \ CPU HPTE / | | + ------------------------------ | | + Boot memory content gets transferred | | + to reserved area by firmware at the | | + time of crash. | | + FADump Header | + (meta area) | + | + | + Metadata: This area holds a metadata struture whose + address is registered with f/w and retrieved in the + second kernel after crash, on platforms that support + tags (OPAL). Having such structure with info needed + to process the crashdump eases dump capture process. + Fig. 1 + o Memory Reservation during second kernel after crash - Low memory Top of memory - 0 boot memory size | - | |<------------- Reserved dump area ----------- -->| - V V V - +-----------+----------/ /---+---+----+-----------+----+------+ - | | |CPU|HPTE| DUMP |ELF | | - +-----------+----------/ /---+---+----+-----------+----+------+ - | | - V V - Used by second /proc/vmcore + Low memory Top of memory + 0 boot memory size | + | |<------------ Crash preserved area ------------>| + V V |<--- Reserved dump area --->| | + +-----------+-----/ /---+---+----+-------+-----+-----+----+--+ + | | |///|////| DUMP | HDR | ELF |////| | + +-----------+-----/ /---+---+----+-------+-----+-----+----+--+ + | | + V V + Used by second /proc/vmcore kernel to boot + + +---+ + |///| -> Regions (CPU, HPTE & Metadata) marked like this in the above + +---+ figures are not always present. For example, OPAL platform + does not have CPU & HPTE regions while Metadata region is + not supported on pSeries currently. + Fig. 2 -Currently the dump will be copied from /proc/vmcore to a -a new file upon user intervention. The dump data available through -/proc/vmcore will be in ELF format. Hence the existing kdump -infrastructure (kdump scripts) to save the dump works fine with -minor modifications. + +Currently the dump will be copied from /proc/vmcore to a new file upon +user intervention. The dump data available through /proc/vmcore will be +in ELF format. Hence the existing kdump infrastructure (kdump scripts) +to save the dump works fine with minor modifications. KDump scripts on +major Distro releases have already been modified to work seemlessly (no +user intervention in saving the dump) when FADump is used, instead of +KDump, as dump mechanism. The tools to examine the dump will be same as the ones used for kdump. -How to enable firmware-assisted dump (fadump): +How to enable firmware-assisted dump (FADump): ---------------------------------------------- 1. Set config option CONFIG_FA_DUMP=y and build kernel. 2. Boot into linux kernel with 'fadump=on' kernel cmdline option. - By default, fadump reserved memory will be initialized as CMA area. + By default, FADump reserved memory will be initialized as CMA area. Alternatively, user can boot linux kernel with 'fadump=nocma' to - prevent fadump to use CMA. + prevent FADump to use CMA. 3. Optionally, user can also set 'crashkernel=' kernel cmdline to specify size of the memory to reserve for boot memory dump preservation. @@ -201,29 +247,29 @@ the control files and debugfs file to display memory reserved region. Here is the list of files under kernel sysfs: /sys/kernel/fadump_enabled - This is used to display the fadump status. + This is used to display the FADump status. - - 0 = fadump is disabled - - 1 = fadump is enabled + - 0 = FADump is disabled + - 1 = FADump is enabled This interface can be used by kdump init scripts to identify if - fadump is enabled in the kernel and act accordingly. + FADump is enabled in the kernel and act accordingly. /sys/kernel/fadump_registered - This is used to display the fadump registration status as well - as to control (start/stop) the fadump registration. + This is used to display the FADump registration status as well + as to control (start/stop) the FADump registration. - - 0 = fadump is not registered. - - 1 = fadump is registered and ready to handle system crash. + - 0 = FADump is not registered. + - 1 = FADump is registered and ready to handle system crash. - To register fadump echo 1 > /sys/kernel/fadump_registered and + To register FADump echo 1 > /sys/kernel/fadump_registered and echo 0 > /sys/kernel/fadump_registered for un-register and stop the - fadump. Once the fadump is un-registered, the system crash will not + FADump. Once the FADump is un-registered, the system crash will not be handled and vmcore will not be captured. This interface can be easily integrated with kdump service start/stop. /sys/kernel/fadump_release_mem - This file is available only when fadump is active during + This file is available only when FADump is active during second kernel. This is used to release the reserved memory region that are held for saving crash dump. To release the reserved memory echo 1 to it:: @@ -237,25 +283,38 @@ Here is the list of files under kernel sysfs: enhanced to use this interface to release the memory reserved for dump and continue without 2nd reboot. + /sys/kernel/fadump_release_opalcore + + This file is available only on OPAL based machines when FADump is + active during capture kernel. This is used to release the memory + used by the kernel to export /sys/firmware/opal/core file. To + release this memory, echo '1' to it: + + echo 1 > /sys/kernel/fadump_release_opalcore + Here is the list of files under powerpc debugfs: (Assuming debugfs is mounted on /sys/kernel/debug directory.) /sys/kernel/debug/powerpc/fadump_region - This file shows the reserved memory regions if fadump is + This file shows the reserved memory regions if FADump is enabled otherwise this file is empty. The output format is:: <region>: [<start>-<end>] <reserved-size> bytes, Dumped: <dump-size> + and for kernel DUMP region is: + + DUMP: Src: <src-addr>, Dest: <dest-addr>, Size: <size>, Dumped: # bytes + e.g. - Contents when fadump is registered during first kernel:: + Contents when FADump is registered during first kernel:: # cat /sys/kernel/debug/powerpc/fadump_region CPU : [0x0000006ffb0000-0x0000006fff001f] 0x40020 bytes, Dumped: 0x0 HPTE: [0x0000006fff0020-0x0000006fff101f] 0x1000 bytes, Dumped: 0x0 DUMP: [0x0000006fff1020-0x0000007fff101f] 0x10000000 bytes, Dumped: 0x0 - Contents when fadump is active during second kernel:: + Contents when FADump is active during second kernel:: # cat /sys/kernel/debug/powerpc/fadump_region CPU : [0x0000006ffb0000-0x0000006fff001f] 0x40020 bytes, Dumped: 0x40020 @@ -263,6 +322,7 @@ Here is the list of files under powerpc debugfs: DUMP: [0x0000006fff1020-0x0000007fff101f] 0x10000000 bytes, Dumped: 0x10000000 : [0x00000010000000-0x0000006ffaffff] 0x5ffb0000 bytes, Dumped: 0x5ffb0000 + NOTE: Please refer to Documentation/filesystems/debugfs.txt on how to mount the debugfs filesystem. @@ -273,7 +333,7 @@ TODO: - Need to come up with the better approach to find out more accurate boot memory size that is required for a kernel to boot successfully when booted with restricted memory. - - The fadump implementation introduces a fadump crash info structure + - The FADump implementation introduces a FADump crash info structure in the scratch area before the ELF core header. The idea of introducing this structure is to pass some important crash info data to the second kernel which will help second kernel to populate ELF core header with diff --git a/Documentation/powerpc/index.rst b/Documentation/powerpc/index.rst index 549b1cdd77ae..db7b6a880f52 100644 --- a/Documentation/powerpc/index.rst +++ b/Documentation/powerpc/index.rst @@ -15,6 +15,7 @@ powerpc dawr-power9 dscr eeh-pci-error-recovery + elfnote firmware-assisted-dump hvcs isa-versions @@ -25,6 +26,7 @@ powerpc qe_firmware syscall64-abi transactional_memory + ultravisor .. only:: subproject and html diff --git a/Documentation/powerpc/ultravisor.rst b/Documentation/powerpc/ultravisor.rst new file mode 100644 index 000000000000..730854f73830 --- /dev/null +++ b/Documentation/powerpc/ultravisor.rst @@ -0,0 +1,1054 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. _ultravisor: + +============================ +Protected Execution Facility +============================ + +.. contents:: + :depth: 3 + +Protected Execution Facility +############################ + + Protected Execution Facility (PEF) is an architectural change for + POWER 9 that enables Secure Virtual Machines (SVMs). DD2.3 chips + (PVR=0x004e1203) or greater will be PEF-capable. A new ISA release + will include the PEF RFC02487 changes. + + When enabled, PEF adds a new higher privileged mode, called Ultravisor + mode, to POWER architecture. Along with the new mode there is new + firmware called the Protected Execution Ultravisor (or Ultravisor + for short). Ultravisor mode is the highest privileged mode in POWER + architecture. + + +------------------+ + | Privilege States | + +==================+ + | Problem | + +------------------+ + | Supervisor | + +------------------+ + | Hypervisor | + +------------------+ + | Ultravisor | + +------------------+ + + PEF protects SVMs from the hypervisor, privileged users, and other + VMs in the system. SVMs are protected while at rest and can only be + executed by an authorized machine. All virtual machines utilize + hypervisor services. The Ultravisor filters calls between the SVMs + and the hypervisor to assure that information does not accidentally + leak. All hypercalls except H_RANDOM are reflected to the hypervisor. + H_RANDOM is not reflected to prevent the hypervisor from influencing + random values in the SVM. + + To support this there is a refactoring of the ownership of resources + in the CPU. Some of the resources which were previously hypervisor + privileged are now ultravisor privileged. + +Hardware +======== + + The hardware changes include the following: + + * There is a new bit in the MSR that determines whether the current + process is running in secure mode, MSR(S) bit 41. MSR(S)=1, process + is in secure mode, MSR(s)=0 process is in normal mode. + + * The MSR(S) bit can only be set by the Ultravisor. + + * HRFID cannot be used to set the MSR(S) bit. If the hypervisor needs + to return to a SVM it must use an ultracall. It can determine if + the VM it is returning to is secure. + + * There is a new Ultravisor privileged register, SMFCTRL, which has an + enable/disable bit SMFCTRL(E). + + * The privilege of a process is now determined by three MSR bits, + MSR(S, HV, PR). In each of the tables below the modes are listed + from least privilege to highest privilege. The higher privilege + modes can access all the resources of the lower privilege modes. + + **Secure Mode MSR Settings** + + +---+---+---+---------------+ + | S | HV| PR|Privilege | + +===+===+===+===============+ + | 1 | 0 | 1 | Problem | + +---+---+---+---------------+ + | 1 | 0 | 0 | Privileged(OS)| + +---+---+---+---------------+ + | 1 | 1 | 0 | Ultravisor | + +---+---+---+---------------+ + | 1 | 1 | 1 | Reserved | + +---+---+---+---------------+ + + **Normal Mode MSR Settings** + + +---+---+---+---------------+ + | S | HV| PR|Privilege | + +===+===+===+===============+ + | 0 | 0 | 1 | Problem | + +---+---+---+---------------+ + | 0 | 0 | 0 | Privileged(OS)| + +---+---+---+---------------+ + | 0 | 1 | 0 | Hypervisor | + +---+---+---+---------------+ + | 0 | 1 | 1 | Problem (Host)| + +---+---+---+---------------+ + + * Memory is partitioned into secure and normal memory. Only processes + that are running in secure mode can access secure memory. + + * The hardware does not allow anything that is not running secure to + access secure memory. This means that the Hypervisor cannot access + the memory of the SVM without using an ultracall (asking the + Ultravisor). The Ultravisor will only allow the hypervisor to see + the SVM memory encrypted. + + * I/O systems are not allowed to directly address secure memory. This + limits the SVMs to virtual I/O only. + + * The architecture allows the SVM to share pages of memory with the + hypervisor that are not protected with encryption. However, this + sharing must be initiated by the SVM. + + * When a process is running in secure mode all hypercalls + (syscall lev=1) go to the Ultravisor. + + * When a process is in secure mode all interrupts go to the + Ultravisor. + + * The following resources have become Ultravisor privileged and + require an Ultravisor interface to manipulate: + + * Processor configurations registers (SCOMs). + + * Stop state information. + + * The debug registers CIABR, DAWR, and DAWRX when SMFCTRL(D) is set. + If SMFCTRL(D) is not set they do not work in secure mode. When set, + reading and writing requires an Ultravisor call, otherwise that + will cause a Hypervisor Emulation Assistance interrupt. + + * PTCR and partition table entries (partition table is in secure + memory). An attempt to write to PTCR will cause a Hypervisor + Emulation Assitance interrupt. + + * LDBAR (LD Base Address Register) and IMC (In-Memory Collection) + non-architected registers. An attempt to write to them will cause a + Hypervisor Emulation Assistance interrupt. + + * Paging for an SVM, sharing of memory with Hypervisor for an SVM. + (Including Virtual Processor Area (VPA) and virtual I/O). + + +Software/Microcode +================== + + The software changes include: + + * SVMs are created from normal VM using (open source) tooling supplied + by IBM. + + * All SVMs start as normal VMs and utilize an ultracall, UV_ESM + (Enter Secure Mode), to make the transition. + + * When the UV_ESM ultracall is made the Ultravisor copies the VM into + secure memory, decrypts the verification information, and checks the + integrity of the SVM. If the integrity check passes the Ultravisor + passes control in secure mode. + + * The verification information includes the pass phrase for the + encrypted disk associated with the SVM. This pass phrase is given + to the SVM when requested. + + * The Ultravisor is not involved in protecting the encrypted disk of + the SVM while at rest. + + * For external interrupts the Ultravisor saves the state of the SVM, + and reflects the interrupt to the hypervisor for processing. + For hypercalls, the Ultravisor inserts neutral state into all + registers not needed for the hypercall then reflects the call to + the hypervisor for processing. The H_RANDOM hypercall is performed + by the Ultravisor and not reflected. + + * For virtual I/O to work bounce buffering must be done. + + * The Ultravisor uses AES (IAPM) for protection of SVM memory. IAPM + is a mode of AES that provides integrity and secrecy concurrently. + + * The movement of data between normal and secure pages is coordinated + with the Ultravisor by a new HMM plug-in in the Hypervisor. + + The Ultravisor offers new services to the hypervisor and SVMs. These + are accessed through ultracalls. + +Terminology +=========== + + * Hypercalls: special system calls used to request services from + Hypervisor. + + * Normal memory: Memory that is accessible to Hypervisor. + + * Normal page: Page backed by normal memory and available to + Hypervisor. + + * Shared page: A page backed by normal memory and available to both + the Hypervisor/QEMU and the SVM (i.e page has mappings in SVM and + Hypervisor/QEMU). + + * Secure memory: Memory that is accessible only to Ultravisor and + SVMs. + + * Secure page: Page backed by secure memory and only available to + Ultravisor and SVM. + + * SVM: Secure Virtual Machine. + + * Ultracalls: special system calls used to request services from + Ultravisor. + + +Ultravisor calls API +#################### + + This section describes Ultravisor calls (ultracalls) needed to + support Secure Virtual Machines (SVM)s and Paravirtualized KVM. The + ultracalls allow the SVMs and Hypervisor to request services from the + Ultravisor such as accessing a register or memory region that can only + be accessed when running in Ultravisor-privileged mode. + + The specific service needed from an ultracall is specified in register + R3 (the first parameter to the ultracall). Other parameters to the + ultracall, if any, are specified in registers R4 through R12. + + Return value of all ultracalls is in register R3. Other output values + from the ultracall, if any, are returned in registers R4 through R12. + The only exception to this register usage is the ``UV_RETURN`` + ultracall described below. + + Each ultracall returns specific error codes, applicable in the context + of the ultracall. However, like with the PowerPC Architecture Platform + Reference (PAPR), if no specific error code is defined for a + particular situation, then the ultracall will fallback to an erroneous + parameter-position based code. i.e U_PARAMETER, U_P2, U_P3 etc + depending on the ultracall parameter that may have caused the error. + + Some ultracalls involve transferring a page of data between Ultravisor + and Hypervisor. Secure pages that are transferred from secure memory + to normal memory may be encrypted using dynamically generated keys. + When the secure pages are transferred back to secure memory, they may + be decrypted using the same dynamically generated keys. Generation and + management of these keys will be covered in a separate document. + + For now this only covers ultracalls currently implemented and being + used by Hypervisor and SVMs but others can be added here when it + makes sense. + + The full specification for all hypercalls/ultracalls will eventually + be made available in the public/OpenPower version of the PAPR + specification. + + .. note:: + + If PEF is not enabled, the ultracalls will be redirected to the + Hypervisor which must handle/fail the calls. + +Ultracalls used by Hypervisor +============================= + + This section describes the virtual memory management ultracalls used + by the Hypervisor to manage SVMs. + +UV_PAGE_OUT +----------- + + Encrypt and move the contents of a page from secure memory to normal + memory. + +Syntax +~~~~~~ + +.. code-block:: c + + uint64_t ultracall(const uint64_t UV_PAGE_OUT, + uint16_t lpid, /* LPAR ID */ + uint64_t dest_ra, /* real address of destination page */ + uint64_t src_gpa, /* source guest-physical-address */ + uint8_t flags, /* flags */ + uint64_t order) /* page size order */ + +Return values +~~~~~~~~~~~~~ + + One of the following values: + + * U_SUCCESS on success. + * U_PARAMETER if ``lpid`` is invalid. + * U_P2 if ``dest_ra`` is invalid. + * U_P3 if the ``src_gpa`` address is invalid. + * U_P4 if any bit in the ``flags`` is unrecognized + * U_P5 if the ``order`` parameter is unsupported. + * U_FUNCTION if functionality is not supported. + * U_BUSY if page cannot be currently paged-out. + +Description +~~~~~~~~~~~ + + Encrypt the contents of a secure-page and make it available to + Hypervisor in a normal page. + + By default, the source page is unmapped from the SVM's partition- + scoped page table. But the Hypervisor can provide a hint to the + Ultravisor to retain the page mapping by setting the ``UV_SNAPSHOT`` + flag in ``flags`` parameter. + + If the source page is already a shared page the call returns + U_SUCCESS, without doing anything. + +Use cases +~~~~~~~~~ + + #. QEMU attempts to access an address belonging to the SVM but the + page frame for that address is not mapped into QEMU's address + space. In this case, the Hypervisor will allocate a page frame, + map it into QEMU's address space and issue the ``UV_PAGE_OUT`` + call to retrieve the encrypted contents of the page. + + #. When Ultravisor runs low on secure memory and it needs to page-out + an LRU page. In this case, Ultravisor will issue the + ``H_SVM_PAGE_OUT`` hypercall to the Hypervisor. The Hypervisor will + then allocate a normal page and issue the ``UV_PAGE_OUT`` ultracall + and the Ultravisor will encrypt and move the contents of the secure + page into the normal page. + + #. When Hypervisor accesses SVM data, the Hypervisor requests the + Ultravisor to transfer the corresponding page into a insecure page, + which the Hypervisor can access. The data in the normal page will + be encrypted though. + +UV_PAGE_IN +---------- + + Move the contents of a page from normal memory to secure memory. + +Syntax +~~~~~~ + +.. code-block:: c + + uint64_t ultracall(const uint64_t UV_PAGE_IN, + uint16_t lpid, /* the LPAR ID */ + uint64_t src_ra, /* source real address of page */ + uint64_t dest_gpa, /* destination guest physical address */ + uint64_t flags, /* flags */ + uint64_t order) /* page size order */ + +Return values +~~~~~~~~~~~~~ + + One of the following values: + + * U_SUCCESS on success. + * U_BUSY if page cannot be currently paged-in. + * U_FUNCTION if functionality is not supported + * U_PARAMETER if ``lpid`` is invalid. + * U_P2 if ``src_ra`` is invalid. + * U_P3 if the ``dest_gpa`` address is invalid. + * U_P4 if any bit in the ``flags`` is unrecognized + * U_P5 if the ``order`` parameter is unsupported. + +Description +~~~~~~~~~~~ + + Move the contents of the page identified by ``src_ra`` from normal + memory to secure memory and map it to the guest physical address + ``dest_gpa``. + + If `dest_gpa` refers to a shared address, map the page into the + partition-scoped page-table of the SVM. If `dest_gpa` is not shared, + copy the contents of the page into the corresponding secure page. + Depending on the context, decrypt the page before being copied. + + The caller provides the attributes of the page through the ``flags`` + parameter. Valid values for ``flags`` are: + + * CACHE_INHIBITED + * CACHE_ENABLED + * WRITE_PROTECTION + + The Hypervisor must pin the page in memory before making + ``UV_PAGE_IN`` ultracall. + +Use cases +~~~~~~~~~ + + #. When a normal VM switches to secure mode, all its pages residing + in normal memory, are moved into secure memory. + + #. When an SVM requests to share a page with Hypervisor the Hypervisor + allocates a page and informs the Ultravisor. + + #. When an SVM accesses a secure page that has been paged-out, + Ultravisor invokes the Hypervisor to locate the page. After + locating the page, the Hypervisor uses UV_PAGE_IN to make the + page available to Ultravisor. + +UV_PAGE_INVAL +------------- + + Invalidate the Ultravisor mapping of a page. + +Syntax +~~~~~~ + +.. code-block:: c + + uint64_t ultracall(const uint64_t UV_PAGE_INVAL, + uint16_t lpid, /* the LPAR ID */ + uint64_t guest_pa, /* destination guest-physical-address */ + uint64_t order) /* page size order */ + +Return values +~~~~~~~~~~~~~ + + One of the following values: + + * U_SUCCESS on success. + * U_PARAMETER if ``lpid`` is invalid. + * U_P2 if ``guest_pa`` is invalid (or corresponds to a secure + page mapping). + * U_P3 if the ``order`` is invalid. + * U_FUNCTION if functionality is not supported. + * U_BUSY if page cannot be currently invalidated. + +Description +~~~~~~~~~~~ + + This ultracall informs Ultravisor that the page mapping in Hypervisor + corresponding to the given guest physical address has been invalidated + and that the Ultravisor should not access the page. If the specified + ``guest_pa`` corresponds to a secure page, Ultravisor will ignore the + attempt to invalidate the page and return U_P2. + +Use cases +~~~~~~~~~ + + #. When a shared page is unmapped from the QEMU's page table, possibly + because it is paged-out to disk, Ultravisor needs to know that the + page should not be accessed from its side too. + + +UV_WRITE_PATE +------------- + + Validate and write the partition table entry (PATE) for a given + partition. + +Syntax +~~~~~~ + +.. code-block:: c + + uint64_t ultracall(const uint64_t UV_WRITE_PATE, + uint32_t lpid, /* the LPAR ID */ + uint64_t dw0 /* the first double word to write */ + uint64_t dw1) /* the second double word to write */ + +Return values +~~~~~~~~~~~~~ + + One of the following values: + + * U_SUCCESS on success. + * U_BUSY if PATE cannot be currently written to. + * U_FUNCTION if functionality is not supported. + * U_PARAMETER if ``lpid`` is invalid. + * U_P2 if ``dw0`` is invalid. + * U_P3 if the ``dw1`` address is invalid. + * U_PERMISSION if the Hypervisor is attempting to change the PATE + of a secure virtual machine or if called from a + context other than Hypervisor. + +Description +~~~~~~~~~~~ + + Validate and write a LPID and its partition-table-entry for the given + LPID. If the LPID is already allocated and initialized, this call + results in changing the partition table entry. + +Use cases +~~~~~~~~~ + + #. The Partition table resides in Secure memory and its entries, + called PATE (Partition Table Entries), point to the partition- + scoped page tables for the Hypervisor as well as each of the + virtual machines (both secure and normal). The Hypervisor + operates in partition 0 and its partition-scoped page tables + reside in normal memory. + + #. This ultracall allows the Hypervisor to register the partition- + scoped and process-scoped page table entries for the Hypervisor + and other partitions (virtual machines) with the Ultravisor. + + #. If the value of the PATE for an existing partition (VM) changes, + the TLB cache for the partition is flushed. + + #. The Hypervisor is responsible for allocating LPID. The LPID and + its PATE entry are registered together. The Hypervisor manages + the PATE entries for a normal VM and can change the PATE entry + anytime. Ultravisor manages the PATE entries for an SVM and + Hypervisor is not allowed to modify them. + +UV_RETURN +--------- + + Return control from the Hypervisor back to the Ultravisor after + processing an hypercall or interrupt that was forwarded (aka + *reflected*) to the Hypervisor. + +Syntax +~~~~~~ + +.. code-block:: c + + uint64_t ultracall(const uint64_t UV_RETURN) + +Return values +~~~~~~~~~~~~~ + + This call never returns to Hypervisor on success. It returns + U_INVALID if ultracall is not made from a Hypervisor context. + +Description +~~~~~~~~~~~ + + When an SVM makes an hypercall or incurs some other exception, the + Ultravisor usually forwards (aka *reflects*) the exceptions to the + Hypervisor. After processing the exception, Hypervisor uses the + ``UV_RETURN`` ultracall to return control back to the SVM. + + The expected register state on entry to this ultracall is: + + * Non-volatile registers are restored to their original values. + * If returning from an hypercall, register R0 contains the return + value (**unlike other ultracalls**) and, registers R4 through R12 + contain any output values of the hypercall. + * R3 contains the ultracall number, i.e UV_RETURN. + * If returning with a synthesized interrupt, R2 contains the + synthesized interrupt number. + +Use cases +~~~~~~~~~ + + #. Ultravisor relies on the Hypervisor to provide several services to + the SVM such as processing hypercall and other exceptions. After + processing the exception, Hypervisor uses UV_RETURN to return + control back to the Ultravisor. + + #. Hypervisor has to use this ultracall to return control to the SVM. + + +UV_REGISTER_MEM_SLOT +-------------------- + + Register an SVM address-range with specified properties. + +Syntax +~~~~~~ + +.. code-block:: c + + uint64_t ultracall(const uint64_t UV_REGISTER_MEM_SLOT, + uint64_t lpid, /* LPAR ID of the SVM */ + uint64_t start_gpa, /* start guest physical address */ + uint64_t size, /* size of address range in bytes */ + uint64_t flags /* reserved for future expansion */ + uint16_t slotid) /* slot identifier */ + +Return values +~~~~~~~~~~~~~ + + One of the following values: + + * U_SUCCESS on success. + * U_PARAMETER if ``lpid`` is invalid. + * U_P2 if ``start_gpa`` is invalid. + * U_P3 if ``size`` is invalid. + * U_P4 if any bit in the ``flags`` is unrecognized. + * U_P5 if the ``slotid`` parameter is unsupported. + * U_PERMISSION if called from context other than Hypervisor. + * U_FUNCTION if functionality is not supported. + + +Description +~~~~~~~~~~~ + + Register a memory range for an SVM. The memory range starts at the + guest physical address ``start_gpa`` and is ``size`` bytes long. + +Use cases +~~~~~~~~~ + + + #. When a virtual machine goes secure, all the memory slots managed by + the Hypervisor move into secure memory. The Hypervisor iterates + through each of memory slots, and registers the slot with + Ultravisor. Hypervisor may discard some slots such as those used + for firmware (SLOF). + + #. When new memory is hot-plugged, a new memory slot gets registered. + + +UV_UNREGISTER_MEM_SLOT +---------------------- + + Unregister an SVM address-range that was previously registered using + UV_REGISTER_MEM_SLOT. + +Syntax +~~~~~~ + +.. code-block:: c + + uint64_t ultracall(const uint64_t UV_UNREGISTER_MEM_SLOT, + uint64_t lpid, /* LPAR ID of the SVM */ + uint64_t slotid) /* reservation slotid */ + +Return values +~~~~~~~~~~~~~ + + One of the following values: + + * U_SUCCESS on success. + * U_FUNCTION if functionality is not supported. + * U_PARAMETER if ``lpid`` is invalid. + * U_P2 if ``slotid`` is invalid. + * U_PERMISSION if called from context other than Hypervisor. + +Description +~~~~~~~~~~~ + + Release the memory slot identified by ``slotid`` and free any + resources allocated towards the reservation. + +Use cases +~~~~~~~~~ + + #. Memory hot-remove. + + +UV_SVM_TERMINATE +---------------- + + Terminate an SVM and release its resources. + +Syntax +~~~~~~ + +.. code-block:: c + + uint64_t ultracall(const uint64_t UV_SVM_TERMINATE, + uint64_t lpid, /* LPAR ID of the SVM */) + +Return values +~~~~~~~~~~~~~ + + One of the following values: + + * U_SUCCESS on success. + * U_FUNCTION if functionality is not supported. + * U_PARAMETER if ``lpid`` is invalid. + * U_INVALID if VM is not secure. + * U_PERMISSION if not called from a Hypervisor context. + +Description +~~~~~~~~~~~ + + Terminate an SVM and release all its resources. + +Use cases +~~~~~~~~~ + + #. Called by Hypervisor when terminating an SVM. + + +Ultracalls used by SVM +====================== + +UV_SHARE_PAGE +------------- + + Share a set of guest physical pages with the Hypervisor. + +Syntax +~~~~~~ + +.. code-block:: c + + uint64_t ultracall(const uint64_t UV_SHARE_PAGE, + uint64_t gfn, /* guest page frame number */ + uint64_t num) /* number of pages of size PAGE_SIZE */ + +Return values +~~~~~~~~~~~~~ + + One of the following values: + + * U_SUCCESS on success. + * U_FUNCTION if functionality is not supported. + * U_INVALID if the VM is not secure. + * U_PARAMETER if ``gfn`` is invalid. + * U_P2 if ``num`` is invalid. + +Description +~~~~~~~~~~~ + + Share the ``num`` pages starting at guest physical frame number ``gfn`` + with the Hypervisor. Assume page size is PAGE_SIZE bytes. Zero the + pages before returning. + + If the address is already backed by a secure page, unmap the page and + back it with an insecure page, with the help of the Hypervisor. If it + is not backed by any page yet, mark the PTE as insecure and back it + with an insecure page when the address is accessed. If it is already + backed by an insecure page, zero the page and return. + +Use cases +~~~~~~~~~ + + #. The Hypervisor cannot access the SVM pages since they are backed by + secure pages. Hence an SVM must explicitly request Ultravisor for + pages it can share with Hypervisor. + + #. Shared pages are needed to support virtio and Virtual Processor Area + (VPA) in SVMs. + + +UV_UNSHARE_PAGE +--------------- + + Restore a shared SVM page to its initial state. + +Syntax +~~~~~~ + +.. code-block:: c + + uint64_t ultracall(const uint64_t UV_UNSHARE_PAGE, + uint64_t gfn, /* guest page frame number */ + uint73 num) /* number of pages of size PAGE_SIZE*/ + +Return values +~~~~~~~~~~~~~ + + One of the following values: + + * U_SUCCESS on success. + * U_FUNCTION if functionality is not supported. + * U_INVALID if VM is not secure. + * U_PARAMETER if ``gfn`` is invalid. + * U_P2 if ``num`` is invalid. + +Description +~~~~~~~~~~~ + + Stop sharing ``num`` pages starting at ``gfn`` with the Hypervisor. + Assume that the page size is PAGE_SIZE. Zero the pages before + returning. + + If the address is already backed by an insecure page, unmap the page + and back it with a secure page. Inform the Hypervisor to release + reference to its shared page. If the address is not backed by a page + yet, mark the PTE as secure and back it with a secure page when that + address is accessed. If it is already backed by an secure page zero + the page and return. + +Use cases +~~~~~~~~~ + + #. The SVM may decide to unshare a page from the Hypervisor. + + +UV_UNSHARE_ALL_PAGES +-------------------- + + Unshare all pages the SVM has shared with Hypervisor. + +Syntax +~~~~~~ + +.. code-block:: c + + uint64_t ultracall(const uint64_t UV_UNSHARE_ALL_PAGES) + +Return values +~~~~~~~~~~~~~ + + One of the following values: + + * U_SUCCESS on success. + * U_FUNCTION if functionality is not supported. + * U_INVAL if VM is not secure. + +Description +~~~~~~~~~~~ + + Unshare all shared pages from the Hypervisor. All unshared pages are + zeroed on return. Only pages explicitly shared by the SVM with the + Hypervisor (using UV_SHARE_PAGE ultracall) are unshared. Ultravisor + may internally share some pages with the Hypervisor without explicit + request from the SVM. These pages will not be unshared by this + ultracall. + +Use cases +~~~~~~~~~ + + #. This call is needed when ``kexec`` is used to boot a different + kernel. It may also be needed during SVM reset. + +UV_ESM +------ + + Secure the virtual machine (*enter secure mode*). + +Syntax +~~~~~~ + +.. code-block:: c + + uint64_t ultracall(const uint64_t UV_ESM, + uint64_t esm_blob_addr, /* location of the ESM blob */ + unint64_t fdt) /* Flattened device tree */ + +Return values +~~~~~~~~~~~~~ + + One of the following values: + + * U_SUCCESS on success (including if VM is already secure). + * U_FUNCTION if functionality is not supported. + * U_INVALID if VM is not secure. + * U_PARAMETER if ``esm_blob_addr`` is invalid. + * U_P2 if ``fdt`` is invalid. + * U_PERMISSION if any integrity checks fail. + * U_RETRY insufficient memory to create SVM. + * U_NO_KEY symmetric key unavailable. + +Description +~~~~~~~~~~~ + + Secure the virtual machine. On successful completion, return + control to the virtual machine at the address specified in the + ESM blob. + +Use cases +~~~~~~~~~ + + #. A normal virtual machine can choose to switch to a secure mode. + +Hypervisor Calls API +#################### + + This document describes the Hypervisor calls (hypercalls) that are + needed to support the Ultravisor. Hypercalls are services provided by + the Hypervisor to virtual machines and Ultravisor. + + Register usage for these hypercalls is identical to that of the other + hypercalls defined in the Power Architecture Platform Reference (PAPR) + document. i.e on input, register R3 identifies the specific service + that is being requested and registers R4 through R11 contain + additional parameters to the hypercall, if any. On output, register + R3 contains the return value and registers R4 through R9 contain any + other output values from the hypercall. + + This document only covers hypercalls currently implemented/planned + for Ultravisor usage but others can be added here when it makes sense. + + The full specification for all hypercalls/ultracalls will eventually + be made available in the public/OpenPower version of the PAPR + specification. + +Hypervisor calls to support Ultravisor +====================================== + + Following are the set of hypercalls needed to support Ultravisor. + +H_SVM_INIT_START +---------------- + + Begin the process of converting a normal virtual machine into an SVM. + +Syntax +~~~~~~ + +.. code-block:: c + + uint64_t hypercall(const uint64_t H_SVM_INIT_START) + +Return values +~~~~~~~~~~~~~ + + One of the following values: + + * H_SUCCESS on success. + +Description +~~~~~~~~~~~ + + Initiate the process of securing a virtual machine. This involves + coordinating with the Ultravisor, using ultracalls, to allocate + resources in the Ultravisor for the new SVM, transferring the VM's + pages from normal to secure memory etc. When the process is + completed, Ultravisor issues the H_SVM_INIT_DONE hypercall. + +Use cases +~~~~~~~~~ + + #. Ultravisor uses this hypercall to inform Hypervisor that a VM + has initiated the process of switching to secure mode. + + +H_SVM_INIT_DONE +--------------- + + Complete the process of securing an SVM. + +Syntax +~~~~~~ + +.. code-block:: c + + uint64_t hypercall(const uint64_t H_SVM_INIT_DONE) + +Return values +~~~~~~~~~~~~~ + + One of the following values: + + * H_SUCCESS on success. + * H_UNSUPPORTED if called from the wrong context (e.g. + from an SVM or before an H_SVM_INIT_START + hypercall). + +Description +~~~~~~~~~~~ + + Complete the process of securing a virtual machine. This call must + be made after a prior call to ``H_SVM_INIT_START`` hypercall. + +Use cases +~~~~~~~~~ + + On successfully securing a virtual machine, the Ultravisor informs + Hypervisor about it. Hypervisor can use this call to finish setting + up its internal state for this virtual machine. + + +H_SVM_PAGE_IN +------------- + + Move the contents of a page from normal memory to secure memory. + +Syntax +~~~~~~ + +.. code-block:: c + + uint64_t hypercall(const uint64_t H_SVM_PAGE_IN, + uint64_t guest_pa, /* guest-physical-address */ + uint64_t flags, /* flags */ + uint64_t order) /* page size order */ + +Return values +~~~~~~~~~~~~~ + + One of the following values: + + * H_SUCCESS on success. + * H_PARAMETER if ``guest_pa`` is invalid. + * H_P2 if ``flags`` is invalid. + * H_P3 if ``order`` of page is invalid. + +Description +~~~~~~~~~~~ + + Retrieve the content of the page, belonging to the VM at the specified + guest physical address. + + Only valid value(s) in ``flags`` are: + + * H_PAGE_IN_SHARED which indicates that the page is to be shared + with the Ultravisor. + + * H_PAGE_IN_NONSHARED indicates that the UV is not anymore + interested in the page. Applicable if the page is a shared page. + + The ``order`` parameter must correspond to the configured page size. + +Use cases +~~~~~~~~~ + + #. When a normal VM becomes a secure VM (using the UV_ESM ultracall), + the Ultravisor uses this hypercall to move contents of each page of + the VM from normal memory to secure memory. + + #. Ultravisor uses this hypercall to ask Hypervisor to provide a page + in normal memory that can be shared between the SVM and Hypervisor. + + #. Ultravisor uses this hypercall to page-in a paged-out page. This + can happen when the SVM touches a paged-out page. + + #. If SVM wants to disable sharing of pages with Hypervisor, it can + inform Ultravisor to do so. Ultravisor will then use this hypercall + and inform Hypervisor that it has released access to the normal + page. + +H_SVM_PAGE_OUT +--------------- + + Move the contents of the page to normal memory. + +Syntax +~~~~~~ + +.. code-block:: c + + uint64_t hypercall(const uint64_t H_SVM_PAGE_OUT, + uint64_t guest_pa, /* guest-physical-address */ + uint64_t flags, /* flags (currently none) */ + uint64_t order) /* page size order */ + +Return values +~~~~~~~~~~~~~ + + One of the following values: + + * H_SUCCESS on success. + * H_PARAMETER if ``guest_pa`` is invalid. + * H_P2 if ``flags`` is invalid. + * H_P3 if ``order`` is invalid. + +Description +~~~~~~~~~~~ + + Move the contents of the page identified by ``guest_pa`` to normal + memory. + + Currently ``flags`` is unused and must be set to 0. The ``order`` + parameter must correspond to the configured page size. + +Use cases +~~~~~~~~~ + + #. If Ultravisor is running low on secure pages, it can move the + contents of some secure pages, into normal pages using this + hypercall. The content will be encrypted. + +References +########## + +- `Supporting Protected Computing on IBM Power Architecture <https://developer.ibm.com/articles/l-support-protected-computing/>`_ |