kernel/linux.git/drivers/hv, branch v7.0.13

hv: utils: handle and propagate errors in kvp_register

2026-06-19T11:48:03+00:00

commit 3fcf923302a8f5c0dc3af3d2ca2657cb5fae4297 upstream. Make kvp_register() return an error code instead of silently ignoring failures, and propagate the error from kvp_handle_handshake() instead of returning success. This propagates both kzalloc_obj() and hvutil_transport_send() failures to kvp_handle_handshake() and thus to kvp_on_msg(). Fixes: 245ba56a52a3 ("Staging: hv: Implement key/value pair (KVP)") Cc: stable@vger.kernel.org Signed-off-by: Thorsten Blum Reviewed-by: Long Li Signed-off-by: Wei Liu Signed-off-by: Greg Kroah-Hartman

Drivers: hv: vmbus: Improve the logic of reserving fb_mmio on Gen2 VMs

2026-06-19T11:48:02+00:00

commit 016a25e4b0df4d77e7c258edee4aaf982e4ee809 upstream. If vmbus_reserve_fb() in the kdump/kexec kernel fails to properly reserve the framebuffer MMIO range (which is below 4GB) due to a Gen2 VM's screen.lfb_base being zero [1], there is an MMIO conflict between the drivers hyperv-drm and pci-hyperv: when the driver pci-hyperv's hv_allocate_config_window() calls vmbus_allocate_mmio() to get an MMIO range, typically it gets a 32-bit MMIO range that overlaps with the framebuffer MMIO range, and later hv_pci_enter_d0() fails with an error message "PCI Pass-through VSP failed D0 Entry with status" since the host thinks that PCI devices must not use MMIO space that the host has assigned to the framebuffer. This is especially an issue if pci-hyperv is built-in and hyperv-drm is built as a module. Consequently, the kdump/kexec kernel fails to detect PCI devices via pci-hyperv, and may fail to mount the root file system, which may reside in a NVMe disk. The issue described here has existed for SR-IOV VF NICs since day one of the pci-hyperv driver, and has been worked around on x64 when possible. With the recent introduction of ARM64 VMs that boot from NVMe, there is no workaround, so we need a formal fix. On Gen2 VMs, if the screen.lfb_base is 0 in the kdump/kexec kernel [1], fall back to the low MMIO base, which should be equal to the framebuffer MMIO base [2] (the statement is true according to my testing on x64 Windows Server 2016, and on x64 and ARM64 Windows Server 2025 and on Azure. I checked with the Hyper-V team and they said the statement should continue to be true for Gen2 VMs). In the first kernel, screen.lfb_base is not 0; if the user specifies a very high resolution, it's not enough to only reserve 8MB: let's always reserve half of the space below 4GB, but cap the reservation to 128MB, which is the required framebuffer size of the highest resolution 7680*4320 supported by Hyper-V. While at it, fix the comparison "end > VTPM_BASE_ADDRESS" by changing the > to >=. Here the 'end' is an inclusive end (typically, it's 0xFFFF_FFFF for the low MMIO range). Note: vmbus_reserve_fb() now also reserves an MMIO range at the beginning of the low MMIO range on CVMs, which have no framebuffers (the 'screen.lfb_base' in vmbus_reserve_fb() is 0 for CVMs), just in case the host might treat the beginning of the low MMIO range specially [3]. BTW, the OpenHCL kernel is not affected by the change, because that kernel boots with DeviceTree rather than ACPI (so vmbus_reserve_fb() won't run there), and there is no framebuffer device for that kernel. Note: normally Gen1 VMs don't have the MMIO conflict issue because the framebuffer MMIO range (which is hardcoded to base=4GB-128MB and size=64MB for Gen1 VMs by the host) is always reported via the legacy PCI graphics device's BAR, so the kdump/kexec kernel can reserve the 64MB MMIO range; however, if the VM is configured to use a very high resolution and the required framebuffer size exceeds 64MB (AFAIK, in practice, this isn't a typical configuration by users), the hyperv-drm driver may need to allocate an MMIO range above 4GB and change the framebuffer MMIO location to the allocated MMIO range -- in this case, there can still be issues [4] which can't be easily fixed: any possible affected Gen1 users would have to use a resolution whose framebuffer size is <= 64MB, or switch to Gen2 VMs. [1] https://lore.kernel.org/all/SA1PR21MB692176C1BC53BFC9EAE5CF8EBF51A@SA1PR21MB6921.namprd21.prod.outlook.com/ [2] https://lore.kernel.org/all/SA1PR21MB69218F955B62DFF62E3E88D2BF222@SA1PR21MB6921.namprd21.prod.outlook.com/ [3] https://lore.kernel.org/all/SN6PR02MB415726B17D5A6027CD1717E8D4342@SN6PR02MB4157.namprd02.prod.outlook.com/ [4] https://lore.kernel.org/all/SA1PR21MB69213486F821CA5A2C793C81BF342@SA1PR21MB6921.namprd21.prod.outlook.com/ Fixes: 4daace0d8ce8 ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V VMs") CC: stable@vger.kernel.org Reviewed-by: Michael Kelley Tested-by: Krister Johansen Tested-by: Matthew Ruffell Signed-off-by: Dexuan Cui Signed-off-by: Wei Liu Signed-off-by: Greg Kroah-Hartman

Drivers: hv: vmbus: Provide option to skip VMBus unload on panic

2026-06-19T11:47:47+00:00

[ Upstream commit c5c3ef8d49e15d2fc1cec4ad7c91d81b99977440 ] Currently, VMBus code initiates a VMBus unload in the panic path so that if a kdump kernel is loaded, it can start fresh in setting up its own VMBus connection. However, a driver for the VMBus virtual frame buffer may need to flush dirty portions of the frame buffer back to the Hyper-V host so that panic information is visible in the graphics console. To support such flushing, provide exported functions for the frame buffer driver to specify that the VMBus unload should not be done by the VMBus driver, and to initiate the VMBus unload itself. Together these allow a frame buffer driver to delay the VMBus unload until after it has completed the flush. Ideally, the VMBus driver could use its own panic-path callback to do the unload after all frame buffer drivers have finished. But DRM frame buffer drivers use the kmsg dump callback, and there are no callbacks after that in the panic path. Hence this somewhat messy approach to properly sequencing the frame buffer flush and the VMBus unload. Fixes: 3671f3777758 ("drm/hyperv: Add support for drm_panic") Signed-off-by: Michael Kelley Reviewed-by: Long Li Signed-off-by: Wei Liu Signed-off-by: Sasha Levin

Drivers: hv: vmbus: fix hyperv_cpuhp_online variable shadowing

2026-05-23T11:09:16+00:00

[ Upstream commit 3c42b33433796b73ddecd8f60bda419b1648d997 ] vmbus_alloc_synic_and_connect() declares a local 'int hyperv_cpuhp_online' that shadows the file-scope global of the same name. The cpuhp state returned by cpuhp_setup_state() is stored in the local, leaving the global at 0 (CPUHP_OFFLINE). When hv_kexec_handler() or hv_machine_shutdown() later call cpuhp_remove_state(hyperv_cpuhp_online) they pass 0, which hits the BUG_ON in __cpuhp_remove_state_cpuslocked(). Remove the local declaration so the cpuhp state is stored in the file-scope global where hv_kexec_handler() and hv_machine_shutdown() expect it. Fixes: 2647c96649ba ("Drivers: hv: Support establishing the confidential VMBus connection") Signed-off-by: Jork Loeser Reviewed-by: Stanislav Kinsburskii Reviewed-by: Anirudh Rayabharam (Microsoft) Signed-off-by: Wei Liu Signed-off-by: Sasha Levin

hv: Select CONFIG_SYSFB only for CONFIG_HYPERV_VMBUS

2026-05-14T13:31:10+00:00

commit d33db956c9618e7cb08c2520ce708437914214ec upstream. 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 Signed-off-by: Greg Kroah-Hartman

mshv_vtl: Fix vmemmap_shift exceeding MAX_FOLIO_ORDER

2026-04-27T13:30:19+00:00

commit 404cd6bffe17e25e0f94ed2775ffdd6cd10ac3fd upstream. When registering VTL0 memory via MSHV_ADD_VTL0_MEMORY, the kernel computes pgmap->vmemmap_shift as the number of trailing zeros in the OR of start_pfn and last_pfn, intending to use the largest compound page order both endpoints are aligned to. However, this value is not clamped to MAX_FOLIO_ORDER, so a sufficiently aligned range (e.g. physical range [0x800000000000, 0x800080000000), corresponding to start_pfn=0x800000000 with 35 trailing zeros) can produce a shift larger than what memremap_pages() accepts, triggering a WARN and returning -EINVAL: WARNING: ... memremap_pages+0x512/0x650 requested folio size unsupported The MAX_FOLIO_ORDER check was added by commit 646b67d57589 ("mm/memremap: reject unreasonable folio/compound page sizes in memremap_pages()"). Fix this by clamping vmemmap_shift to MAX_FOLIO_ORDER so we always request the largest order the kernel supports, in those cases, rather than an out-of-range value. Also fix the error path to propagate the actual error code from devm_memremap_pages() instead of hard-coding -EFAULT, which was masking the real -EINVAL return. Fixes: 7bfe3b8ea6e3 ("Drivers: hv: Introduce mshv_vtl driver") Cc: stable@vger.kernel.org Signed-off-by: Naman Jain Reviewed-by: Michael Kelley Signed-off-by: Wei Liu Signed-off-by: Greg Kroah-Hartman

mshv: Fix infinite fault loop on permission-denied GPA intercepts

2026-04-04T05:25:53+00:00

Prevent infinite fault loops when guests access memory regions without proper permissions. Currently, mshv_handle_gpa_intercept() attempts to remap pages for all faults on movable memory regions, regardless of whether the access type is permitted. When a guest writes to a read-only region, the remap succeeds but the region remains read-only, causing immediate re-fault and spinning the vCPU indefinitely. Validate intercept access type against region permissions before attempting remaps. Reject writes to non-writable regions and executes to non-executable regions early, returning false to let the VMM handle the intercept appropriately. This also closes a potential DoS vector where malicious guests could intentionally trigger these fault loops to consume host resources. Fixes: b9a66cd5ccbb ("mshv: Add support for movable memory regions") Signed-off-by: Stanislav Kinsburskii Reviewed-by: Anirudh Rayabharam (Microsoft) Signed-off-by: Wei Liu

mshv: Fix error handling in mshv_region_pin

2026-03-18T16:18:49+00:00

The current error handling has two issues: First, pin_user_pages_fast() can return a short pin count (less than requested but greater than zero) when it cannot pin all requested pages. This is treated as success, leading to partially pinned regions being used, which causes memory corruption. Second, when an error occurs mid-loop, already pinned pages from the current batch are not properly accounted for before calling mshv_region_invalidate_pages(), causing a page reference leak. Treat short pins as errors and fix partial batch accounting before cleanup. Signed-off-by: Stanislav Kinsburskii Reviewed-by: Michael Kelley Signed-off-by: Wei Liu

mshv: Fix use-after-free in mshv_map_user_memory error path

2026-03-13T21:11:18+00:00

In the error path of mshv_map_user_memory(), calling vfree() directly on the region leaves the MMU notifier registered. When userspace later unmaps the memory, the notifier fires and accesses the freed region, causing a use-after-free and potential kernel panic. Replace vfree() with mshv_partition_put() to properly unregister the MMU notifier before freeing the region. Fixes: b9a66cd5ccbb9 ("mshv: Add support for movable memory regions") Signed-off-by: Stanislav Kinsburskii Signed-off-by: Wei Liu

mshv: pass struct mshv_user_mem_region by reference

2026-03-12T04:32:21+00:00

For unstated reasons, function mshv_partition_ioctl_set_memory passes struct mshv_user_mem_region by value instead of by reference. Change it to pass by reference. Signed-off-by: Mukesh R Reviewed-by: Michael Kelley Signed-off-by: Wei Liu