kernel/linux.git/drivers/hv/Kconfig, branch v6.18.22

Drivers: hv: Make CONFIG_HYPERV bool

2025-10-01T00:00:45+00:00

With CONFIG_HYPERV and CONFIG_HYPERV_VMBUS separated, change CONFIG_HYPERV to bool from tristate. CONFIG_HYPERV now becomes the core Hyper-V hypervisor support, such as hypercalls, clocks/timers, Confidential Computing setup, PCI passthru, etc. that doesn't involve VMBus or VMBus devices. Signed-off-by: Mukesh Rathor Signed-off-by: Wei Liu

Drivers: hv: Add CONFIG_HYPERV_VMBUS option

2025-10-01T00:00:42+00:00

At present VMBus driver is hinged off of CONFIG_HYPERV which entails lot of builtin code and encompasses too much. It's not always clear what depends on builtin hv code and what depends on VMBus. Setting CONFIG_HYPERV as a module and fudging the Makefile to switch to builtin adds even more confusion. VMBus is an independent module and should have its own config option. Also, there are scenarios like baremetal dom0/root where support is built in with CONFIG_HYPERV but without VMBus. Lastly, there are more features coming down that use CONFIG_HYPERV and add more dependencies on it. So, create a fine grained HYPERV_VMBUS option and update Kconfigs for dependency on VMBus. Signed-off-by: Mukesh Rathor Acked-by: Bjorn Helgaas # drivers/pci Signed-off-by: Wei Liu

x86/hyperv: Switch to msi_create_parent_irq_domain()

2025-09-30T22:50:48+00:00

Move away from the legacy MSI domain setup, switch to use msi_create_parent_irq_domain(). While doing the conversion, I noticed that hv_irq_compose_msi_msg() is doing more than it is supposed to (composing message content). The interrupt allocation bits should be moved into hv_msi_domain_alloc(). However, I have no hardware to test this change, therefore I leave a TODO note. Signed-off-by: Nam Cao Acked-by: Thomas Gleixner Tested-by: Nuno Das Neves Reviewed-by: Nuno Das Neves Signed-off-by: Wei Liu

mshv: Use common "entry virt" APIs to do work in root before running guest

2025-09-30T22:50:48+00:00

Use the kernel's common "entry virt" APIs to handle pending work prior to (re)entering guest mode, now that the virt APIs don't have a superfluous dependency on KVM. No functional change intended. Signed-off-by: Sean Christopherson Tested-by: Nuno Das Neves Reviewed-by: Nuno Das Neves Signed-off-by: Wei Liu

Drivers: hv: Select CONFIG_SYSFB only if EFI is enabled

2025-07-09T22:39:40+00:00

Commit 96959283a58d ("Drivers: hv: Always select CONFIG_SYSFB for Hyper-V guests") selects CONFIG_SYSFB for Hyper-V guests so that screen_info is available to the VMBus driver to get the location of the framebuffer in Generation 2 VMs. However, if CONFIG_HYPERV is enabled but CONFIG_EFI is not, a kernel link error results in ARM64 builds because screen_info is provided by the EFI firmware interface. While configuring an ARM64 Hyper-V guest without EFI isn't useful since EFI is required to boot, the configuration is still possible and the link error should be prevented. Fix this by making the selection of CONFIG_SYSFB conditional on CONFIG_EFI being defined. For Generation 1 VMs on x86/x64, which don't use EFI, the additional condition is OK because such VMs get the framebuffer information via a mechanism that doesn't use screen_info. Fixes: 96959283a58d ("Drivers: hv: Always select CONFIG_SYSFB for Hyper-V guests") Reported-by: Arnd Bergmann Closes: https://lore.kernel.org/linux-hyperv/20250610091810.2638058-1-arnd@kernel.org/ Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202506080820.1wmkQufc-lkp@intel.com/ Signed-off-by: Michael Kelley Link: https://lore.kernel.org/stable/20250613230059.380483-1-mhklinux%40outlook.com Reviewed-by: Roman Kisel Link: https://lore.kernel.org/r/20250613230059.380483-1-mhklinux@outlook.com Signed-off-by: Wei Liu Message-ID: <20250613230059.380483-1-mhklinux@outlook.com>

Drivers: hv: Always select CONFIG_SYSFB for Hyper-V guests

2025-05-23T16:39:37+00:00

The Hyper-V host provides guest VMs with a range of MMIO addresses that guest VMBus drivers can use. The VMBus driver in Linux manages that MMIO space, and allocates portions to drivers upon request. As part of managing that MMIO space in a Generation 2 VM, the VMBus driver must reserve the portion of the MMIO space that Hyper-V has designated for the synthetic frame buffer, and not allocate this space to VMBus drivers other than graphics framebuffer drivers. The synthetic frame buffer MMIO area is described by the screen_info data structure that is passed to the Linux kernel at boot time, so the VMBus driver must access screen_info for Generation 2 VMs. (In Generation 1 VMs, the framebuffer MMIO space is communicated to the guest via a PCI pseudo-device, and access to screen_info is not needed.) In commit a07b50d80ab6 ("hyperv: avoid dependency on screen_info") the VMBus driver's access to screen_info is restricted to when CONFIG_SYSFB is enabled. CONFIG_SYSFB is typically enabled in kernels built for Hyper-V by virtue of having at least one of CONFIG_FB_EFI, CONFIG_FB_VESA, or CONFIG_SYSFB_SIMPLEFB enabled, so the restriction doesn't usually affect anything. But it's valid to have none of these enabled, in which case CONFIG_SYSFB is not enabled, and the VMBus driver is unable to properly reserve the framebuffer MMIO space for graphics framebuffer drivers. The framebuffer MMIO space may be assigned to some other VMBus driver, with undefined results. As an example, if a VM is using a PCI pass-thru NVMe controller to host the OS disk, the PCI NVMe controller is probed before any graphics devices, and the NVMe controller is assigned a portion of the framebuffer MMIO space. Hyper-V reports an error to Linux during the probe, and the OS disk fails to get setup. Then Linux fails to boot in the VM. Fix this by having CONFIG_HYPERV always select SYSFB. Then the VMBus driver in a Gen 2 VM can always reserve the MMIO space for the graphics framebuffer driver, and prevent the undefined behavior. But don't select SYSFB when building for HYPERV_VTL_MODE as VTLs other than VTL 0 don't have a framebuffer and aren't subject to the issue. Adding SYSFB in such cases is harmless, but would increase the image size for no purpose. Fixes: a07b50d80ab6 ("hyperv: avoid dependency on screen_info") Signed-off-by: Michael Kelley Reviewed-by: Saurabh Sengar Link: https://lore.kernel.org/stable/20250520040143.6964-1-mhklinux%40outlook.com Link: https://lore.kernel.org/r/20250520040143.6964-1-mhklinux@outlook.com Signed-off-by: Wei Liu Message-ID: <20250520040143.6964-1-mhklinux@outlook.com>

Drivers: hv: Enable VTL mode for arm64

2025-05-23T16:30:55+00:00

Kconfig dependencies for arm64 guests on Hyper-V require that be ACPI enabled, and limit VTL mode to x86/x64. To enable VTL mode on arm64 as well, update the dependencies. Since VTL mode requires DeviceTree instead of ACPI, don’t require arm64 guests on Hyper-V to have ACPI unconditionally. Signed-off-by: Roman Kisel Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20250428210742.435282-4-romank@linux.microsoft.com Signed-off-by: Wei Liu Message-ID: <20250428210742.435282-4-romank@linux.microsoft.com>

Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs

2025-03-21T18:24:22+00:00

Provide a set of IOCTLs for creating and managing child partitions when running as root partition on Hyper-V. The new driver is enabled via CONFIG_MSHV_ROOT. A brief overview of the interface: MSHV_CREATE_PARTITION is the entry point, returning a file descriptor representing a child partition. IOCTLs on this fd can be used to map memory, create VPs, etc. Creating a VP returns another file descriptor representing that VP which in turn has another set of corresponding IOCTLs for running the VP, getting/setting state, etc. MSHV_ROOT_HVCALL is a generic "passthrough" hypercall IOCTL which can be used for a number of partition or VP hypercalls. This is for hypercalls that do not affect any state in the kernel driver, such as getting and setting VP registers and partition properties, translating addresses, etc. It is "passthrough" because the binary input and output for the hypercall is only interpreted by the VMM - the kernel driver does nothing but insert the VP and partition id where necessary (which are always in the same place), and execute the hypercall. Co-developed-by: Anirudh Rayabharam Signed-off-by: Anirudh Rayabharam Co-developed-by: Jinank Jain Signed-off-by: Jinank Jain Co-developed-by: Mukesh Rathor Signed-off-by: Mukesh Rathor Co-developed-by: Muminul Islam Signed-off-by: Muminul Islam Co-developed-by: Praveen K Paladugu Signed-off-by: Praveen K Paladugu Co-developed-by: Stanislav Kinsburskii Signed-off-by: Stanislav Kinsburskii Co-developed-by: Wei Liu Signed-off-by: Nuno Das Neves Reviewed-by: Roman Kisel Link: https://lore.kernel.org/r/1741980536-3865-11-git-send-email-nunodasneves@linux.microsoft.com Signed-off-by: Wei Liu Message-ID: <1741980536-3865-11-git-send-email-nunodasneves@linux.microsoft.com>

hyperv: Add CONFIG_MSHV_ROOT to gate root partition support

2025-03-20T21:22:58+00:00

CONFIG_MSHV_ROOT allows kernels built to run as a normal Hyper-V guest to exclude the root partition code, which is expected to grow significantly over time. This option is a tristate so future driver code can be built as a (m)odule, allowing faster development iteration cycles. If CONFIG_MSHV_ROOT is disabled, don't compile hv_proc.c, and stub hv_root_partition() to return false unconditionally. This allows the compiler to optimize away root partition code blocks since they will be disabled at compile time. In the case of booting as root partition *without* CONFIG_MSHV_ROOT enabled, print a critical error (the kernel will likely crash). Signed-off-by: Nuno Das Neves Reviewed-by: Easwar Hariharan Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/1740167795-13296-4-git-send-email-nunodasneves@linux.microsoft.com Signed-off-by: Wei Liu Message-ID: <1740167795-13296-4-git-send-email-nunodasneves@linux.microsoft.com>

x86/hyperv: Use per cpu initial stack for vtl context

2024-03-08T23:40:09+00:00

Currently, the secondary CPUs in Hyper-V VTL context lack support for parallel startup. Therefore, relying on the single initial_stack fetched from the current task structure suffices for all vCPUs. However, common initial_stack risks stack corruption when parallel startup is enabled. In order to facilitate parallel startup, use the initial_stack from the per CPU idle thread instead of the current task. Fixes: 3be1bc2fe9d2 ("x86/hyperv: VTL support for Hyper-V") Signed-off-by: Saurabh Sengar Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/1709452896-13342-1-git-send-email-ssengar@linux.microsoft.com Signed-off-by: Wei Liu Message-ID: <1709452896-13342-1-git-send-email-ssengar@linux.microsoft.com>