kernel/linux.git/drivers/hv/Kconfig, branch v7.1

mshv: Add conditional VMBus dependency

2026-05-27T22:11:05+00:00

When the VMBus driver is not part of the kernel (CONFIG_HYPERV_VMBUS=n), the MSHV root driver fails to link: ERROR: modpost: "hv_vmbus_exists" [drivers/hv/mshv_root.ko] undefined! Fix this while meeting these requirements: * It must be possible to include the MSHV root driver without the VMBus driver. In such case, the MSHV root driver can be built-in to the kernel image, or it can be built as a separate module. * If both the MSHV root driver and the VMBus driver are present, the MSHV root driver and VMBus driver can both be built-in, or they can both be separate modules. Or the MSHV root driver can be a module while the VMBus driver can be built-in, but the reverse is disallowed. Regardless of the build choices, the VMBus driver must be loaded before the MSHV driver in order for the SynIC to be managed properly (see comments in the MSHV SynIC code). The fix has two parts: * Add a Kconfig entry for MSHV_ROOT to depend on HYPERV_VMBUS if HYPERV_VMBUS is present. The entry disallows MSHV_ROOT being built-in when HYPERV_VMBUS is a module, but without requiring that HYPERV_VMBUS be built. * Add a stub implementation of hv_vmbus_exists() for when the VMBus driver is not present so that the MSHV root driver has no module dependency on VMBus. When the VMBus driver *is* present, the module dependency ensures that the VMBus driver loads first when both are built as modules. Existing code ensures that the VMBus driver loads first if it is built-in. The VMBus driver uses subsys_initcall(), which is initcall level 4. The MSHV root driver uses module_init(), which becomes device_init() when built-in, and device_init() is initcall level 6. Reported-by: Arnd Bergmann Closes: https://lore.kernel.org/all/20260520074044.923728-1-arnd@kernel.org/ Signed-off-by: Michael Kelley Acked-by: Arnd Bergmann Reviewed-by: Jork Loeser Reviewed-by: Hardik Garg Signed-off-by: Wei Liu

hv: Select CONFIG_SYSFB only for CONFIG_HYPERV_VMBUS

2026-04-15T13:37:09+00:00

Hyperv's sysfb access only exists in the VMBUS support. Therefore only select CONFIG_SYSFB for CONFIG_HYPERV_VMBUS. Avoids sysfb code on systems that don't need it. Signed-off-by: Thomas Zimmermann Fixes: 96959283a58d ("Drivers: hv: Always select CONFIG_SYSFB for Hyper-V guests") Cc: Michael Kelley Cc: Saurabh Sengar Cc: Wei Liu Cc: "K. Y. Srinivasan" Cc: Haiyang Zhang Cc: Dexuan Cui Cc: Long Li Cc: linux-hyperv@vger.kernel.org Cc: # v6.16+ Reviewed-by: Saurabh Sengar Link: https://patch.msgid.link/20260402092305.208728-2-tzimmermann@suse.de

mshv: Add support for movable memory regions

2025-12-05T23:20:49+00:00

Introduce support for movable memory regions in the Hyper-V root partition driver to improve memory management flexibility and enable advanced use cases such as dynamic memory remapping. Mirror the address space between the Linux root partition and guest VMs using HMM. The root partition owns the memory, while guest VMs act as devices with page tables managed via hypercalls. MSHV handles VP intercepts by invoking hmm_range_fault() and updating SLAT entries. When memory is reclaimed, HMM invalidates the relevant regions, prompting MSHV to clear SLAT entries; guest VMs will fault again on access. Integrate mmu_interval_notifier for movable regions, implement handlers for HMM faults and memory invalidation, and update memory region mapping logic to support movable regions. While MMU notifiers are commonly used in virtualization drivers, this implementation leverages HMM (Heterogeneous Memory Management) for its specialized functionality. HMM provides a framework for mirroring, invalidation, and fault handling, reducing boilerplate and improving maintainability compared to generic MMU notifiers. Signed-off-by: Stanislav Kinsburskii Reviewed-by: Nuno Das Neves Signed-off-by: Wei Liu

Drivers: hv: Introduce mshv_vtl driver

2025-12-05T23:16:26+00:00

Provide an interface for Virtual Machine Monitor like OpenVMM and its use as OpenHCL paravisor to control VTL0 (Virtual trust Level). Expose devices and support IOCTLs for features like VTL creation, VTL0 memory management, context switch, making hypercalls, mapping VTL0 address space to VTL2 userspace, getting new VMBus messages and channel events in VTL2 etc. Co-developed-by: Roman Kisel Signed-off-by: Roman Kisel Co-developed-by: Saurabh Sengar Signed-off-by: Saurabh Sengar Reviewed-by: Michael Kelley Signed-off-by: Naman Jain Signed-off-by: Wei Liu

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>