kernel/linux.git/include/uapi/linux/kvm.h, branch v6.18.21

KVM: guest_memfd: Add INIT_SHARED flag, reject user page faults if not set

2025-10-10T21:25:23+00:00

Add a guest_memfd flag to allow userspace to state that the underlying memory should be configured to be initialized as shared, and reject user page faults if the guest_memfd instance's memory isn't shared. Because KVM doesn't yet support in-place private<=>shared conversions, all guest_memfd memory effectively follows the initial state. Alternatively, KVM could deduce the initial state based on MMAP, which for all intents and purposes is what KVM currently does. However, implicitly deriving the default state based on MMAP will result in a messy ABI when support for in-place conversions is added. For x86 CoCo VMs, which don't yet support MMAP, memory is currently private by default (otherwise the memory would be unusable). If MMAP implies memory is shared by default, then the default state for CoCo VMs will vary based on MMAP, and from userspace's perspective, will change when in-place conversion support is added. I.e. to maintain guest<=>host ABI, userspace would need to immediately convert all memory from shared=>private, which is both ugly and inefficient. The inefficiency could be avoided by adding a flag to state that memory is _private_ by default, irrespective of MMAP, but that would lead to an equally messy and hard to document ABI. Bite the bullet and immediately add a flag to control the default state so that the effective behavior is explicit and straightforward. Fixes: 3d3a04fad25a ("KVM: Allow and advertise support for host mmap() on guest_memfd files") Cc: David Hildenbrand Reviewed-by: Fuad Tabba Tested-by: Fuad Tabba Reviewed-by: Ackerley Tng Tested-by: Ackerley Tng Reviewed-by: David Hildenbrand Link: https://lore.kernel.org/r/20251003232606.4070510-3-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: Rework KVM_CAP_GUEST_MEMFD_MMAP into KVM_CAP_GUEST_MEMFD_FLAGS

2025-10-10T21:25:22+00:00

Rework the not-yet-released KVM_CAP_GUEST_MEMFD_MMAP into a more generic KVM_CAP_GUEST_MEMFD_FLAGS capability so that adding new flags doesn't require a new capability, and so that developers aren't tempted to bundle multiple flags into a single capability. Note, kvm_vm_ioctl_check_extension_generic() can only return a 32-bit value, but that limitation can be easily circumvented by adding e.g. KVM_CAP_GUEST_MEMFD_FLAGS2 in the unlikely event guest_memfd supports more than 32 flags. Reviewed-by: Ackerley Tng Tested-by: Ackerley Tng Reviewed-by: David Hildenbrand Link: https://lore.kernel.org/r/20251003232606.4070510-2-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: Allow and advertise support for host mmap() on guest_memfd files

2025-08-27T08:37:03+00:00

Now that all the x86 and arm64 plumbing for mmap() on guest_memfd is in place, allow userspace to set GUEST_MEMFD_FLAG_MMAP and advertise support via a new capability, KVM_CAP_GUEST_MEMFD_MMAP. The availability of this capability is determined per architecture, and its enablement for a specific guest_memfd instance is controlled by the GUEST_MEMFD_FLAG_MMAP flag at creation time. Update the KVM API documentation to detail the KVM_CAP_GUEST_MEMFD_MMAP capability, the associated GUEST_MEMFD_FLAG_MMAP, and provide essential information regarding support for mmap in guest_memfd. Reviewed-by: David Hildenbrand Reviewed-by: Gavin Shan Reviewed-by: Shivank Garg Reviewed-by: Xiaoyao Li Signed-off-by: Fuad Tabba Signed-off-by: Sean Christopherson Message-ID: <20250729225455.670324-22-seanjc@google.com> Signed-off-by: Paolo Bonzini

Merge tag 'kvmarm-6.17' of https://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD

2025-07-29T16:27:40+00:00

KVM/arm64 changes for 6.17, round #1 - Host driver for GICv5, the next generation interrupt controller for arm64, including support for interrupt routing, MSIs, interrupt translation and wired interrupts. - Use FEAT_GCIE_LEGACY on GICv5 systems to virtualize GICv3 VMs on GICv5 hardware, leveraging the legacy VGIC interface. - Userspace control of the 'nASSGIcap' GICv3 feature, allowing userspace to disable support for SGIs w/o an active state on hardware that previously advertised it unconditionally. - Map supporting endpoints with cacheable memory attributes on systems with FEAT_S2FWB and DIC where KVM no longer needs to perform cache maintenance on the address range. - Nested support for FEAT_RAS and FEAT_DoubleFault2, allowing the guest hypervisor to inject external aborts into an L2 VM and take traps of masked external aborts to the hypervisor. - Convert more system register sanitization to the config-driven implementation. - Fixes to the visibility of EL2 registers, namely making VGICv3 system registers accessible through the VGIC device instead of the ONE_REG vCPU ioctls. - Various cleanups and minor fixes.

KVM: x86: Provide a capability to disable APERF/MPERF read intercepts

2025-07-09T16:33:37+00:00

Allow a guest to read the physical IA32_APERF and IA32_MPERF MSRs without interception. The IA32_APERF and IA32_MPERF MSRs are not virtualized. Writes are not handled at all. The MSR values are not zeroed on vCPU creation, saved on suspend, or restored on resume. No accommodation is made for processor migration or for sharing a logical processor with other tasks. No adjustments are made for non-unit TSC multipliers. The MSRs do not account for time the same way as the comparable PMU events, whether the PMU is virtualized by the traditional emulation method or the new mediated pass-through approach. Nonetheless, in a properly constrained environment, this capability can be combined with a guest CPUID table that advertises support for CPUID.6:ECX.APERFMPERF[bit 0] to induce a Linux guest to report the effective physical CPU frequency in /proc/cpuinfo. Moreover, there is no performance cost for this capability. Signed-off-by: Jim Mattson Link: https://lore.kernel.org/r/20250530185239.2335185-3-jmattson@google.com Reviewed-by: Xiaoyao Li Link: https://lore.kernel.org/r/20250626001225.744268-3-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: arm64: Expose new KVM cap for cacheable PFNMAP

2025-07-07T23:54:52+00:00

Introduce a new KVM capability to expose to the userspace whether cacheable mapping of PFNMAP is supported. The ability to safely do the cacheable mapping of PFNMAP is contingent on S2FWB and ARM64_HAS_CACHE_DIC. S2FWB allows KVM to avoid flushing the D cache, ARM64_HAS_CACHE_DIC allows KVM to avoid flushing the icache and turns icache_inval_pou() into a NOP. The cap would be false if those requirements are missing and is checked by making use of kvm_arch_supports_cacheable_pfnmap. This capability would allow userspace to discover the support. It could for instance be used by userspace to prevent live-migration across FWB and non-FWB hosts. CC: Catalin Marinas CC: Jason Gunthorpe CC: Oliver Upton CC: David Hildenbrand Suggested-by: Marc Zyngier Reviewed-by: Jason Gunthorpe Tested-by: Donald Dutile Signed-off-by: Ankit Agrawal Reviewed-by: Catalin Marinas Link: https://lore.kernel.org/r/20250705071717.5062-7-ankita@nvidia.com Signed-off-by: Oliver Upton

KVM: TDX: Exit to userspace for SetupEventNotifyInterrupt

2025-06-20T18:09:50+00:00

Signed-off-by: Paolo Bonzini

KVM: TDX: Exit to userspace for GetTdVmCallInfo

2025-06-20T17:55:47+00:00

Exit to userspace for TDG.VP.VMCALL via KVM_EXIT_TDX, to allow userspace to provide information about the support of TDVMCALLs when r12 is 1 for the TDVMCALLs beyond the GHCI base API. GHCI spec defines the GHCI base TDVMCALLs: , , , , <#VE.RequestMMIO>, , , and . They must be supported by VMM to support TDX guests. For GetTdVmCallInfo - When leaf (r12) to enumerate TDVMCALL functionality is set to 0, successful execution indicates all GHCI base TDVMCALLs listed above are supported. Update the KVM TDX document with the set of the GHCI base APIs. - When leaf (r12) to enumerate TDVMCALL functionality is set to 1, it indicates the TDX guest is querying the supported TDVMCALLs beyond the GHCI base TDVMCALLs. Exit to userspace to let userspace set the TDVMCALL sub-function bit(s) accordingly to the leaf outputs. KVM could set the TDVMCALL bit(s) supported by itself when the TDVMCALLs don't need support from userspace after returning from userspace and before entering guest. Currently, no such TDVMCALLs implemented, KVM just sets the values returned from userspace. Suggested-by: Paolo Bonzini Signed-off-by: Binbin Wu [Adjust userspace API. - Paolo] Signed-off-by: Paolo Bonzini

KVM: TDX: Handle TDG.VP.VMCALL

2025-06-20T17:09:32+00:00

Handle TDVMCALL for GetQuote to generate a TD-Quote. GetQuote is a doorbell-like interface used by TDX guests to request VMM to generate a TD-Quote signed by a service hosting TD-Quoting Enclave operating on the host. A TDX guest passes a TD Report (TDREPORT_STRUCT) in a shared-memory area as parameter. Host VMM can access it and queue the operation for a service hosting TD-Quoting enclave. When completed, the Quote is returned via the same shared-memory area. KVM only checks the GPA from the TDX guest has the shared-bit set and drops the shared-bit before exiting to userspace to avoid bleeding the shared-bit into KVM's exit ABI. KVM forwards the request to userspace VMM (e.g. QEMU) and userspace VMM queues the operation asynchronously. KVM sets the return code according to the 'ret' field set by userspace to notify the TDX guest whether the request has been queued successfully or not. When the request has been queued successfully, the TDX guest can poll the status field in the shared-memory area to check whether the Quote generation is completed or not. When completed, the generated Quote is returned via the same buffer. Add KVM_EXIT_TDX as a new exit reason to userspace. Userspace is required to handle the KVM exit reason as the initial support for TDX, by reentering KVM to ensure that the TDVMCALL is complete. While at it, add a note that KVM_EXIT_HYPERCALL also requires reentry with KVM_RUN. Signed-off-by: Binbin Wu Tested-by: Mikko Ylinen Acked-by: Kai Huang [Adjust userspace API. - Paolo] Signed-off-by: Paolo Bonzini

Merge tag 'kvm-riscv-6.16-1' of https://github.com/kvm-riscv/linux into HEAD

2025-05-26T20:27:00+00:00

KVM/riscv changes for 6.16 - Add vector registers to get-reg-list selftest - VCPU reset related improvements - Remove scounteren initialization from VCPU reset - Support VCPU reset from userspace using set_mpstate() ioctl