kernel/linux.git/drivers/hv/hyperv_vmbus.h, branch linux-7.1.y

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

2026-05-13T22:29:32+00:00

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

Merge tag 'hyperv-next-signed-20260421' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux

2026-04-22T16:50:46+00:00

Pull Hyper-V updates from Wei Liu: - Fix cross-compilation for hv tools (Aditya Garg) - Fix vmemmap_shift exceeding MAX_FOLIO_ORDER in mshv_vtl (Naman Jain) - Limit channel interrupt scan to relid high water mark (Michael Kelley) - Export hv_vmbus_exists() and use it in pci-hyperv (Dexuan Cui) - Fix cleanup and shutdown issues for MSHV (Jork Loeser) - Introduce more tracing support for MSHV (Stanislav Kinsburskii) * tag 'hyperv-next-signed-20260421' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux: x86/hyperv: Skip LP/VP creation on kexec x86/hyperv: move stimer cleanup to hv_machine_shutdown() Drivers: hv: vmbus: fix hyperv_cpuhp_online variable shadowing mshv: Add tracepoint for GPA intercept handling mshv_vtl: Fix vmemmap_shift exceeding MAX_FOLIO_ORDER tools: hv: Fix cross-compilation Drivers: hv: vmbus: Export hv_vmbus_exists() and use it in pci-hyperv mshv: Introduce tracing support Drivers: hv: vmbus: Limit channel interrupt scan to relid high water mark

Drivers: hv: vmbus: Limit channel interrupt scan to relid high water mark

2026-04-14T04:42:02+00:00

When checking for VMBus channel interrupts, current code always scans the full SynIC receive interrupt bit array to get the relid of the interrupting channels. The array has HV_EVENT_FLAGS_COUNT (2048) bits. But VMs rarely have more than 100 channels, and the relid is typically a small integer that is densely assigned by the Hyper-V host. It's wasteful to scan 2048 bits when it is highly unlikely that anything will be found past bit 100. The waste is double with Confidential VMBus because there are two receive interrupt arrays that must be scanned: one for the hypervisor SynIC and one for the paravisor SynIC. Improve the scanning by tracking the largest relid that has been offered by the Hyper-V host. Then when checking for VMBus channel interrupts, only scan up to this high water mark. When channels are rescinded, it's not worth the complexity to recalculate the high water mark. Hyper-V tends to reuse the rescinded relids for any new channels that are subsequently added, and the performance benefit of exactly tracking the high water mark would be minimal. Signed-off-by: Michael Kelley Tested-by: Roman Kisel Reviewed-by: Roman Kisel Signed-off-by: Wei Liu

drivers: hv: vmbus: replace deprecated mmap hook with mmap_prepare

2026-04-05T20:53:44+00:00

The f_op->mmap interface is deprecated, so update the vmbus driver to use its successor, mmap_prepare. This updates all callbacks which referenced the function pointer hv_mmap_ring_buffer to instead reference hv_mmap_prepare_ring_buffer, utilising the newly introduced compat_set_desc_from_vma() and __compat_vma_mmap() to be able to implement this change. The UIO HV generic driver is the only user of hv_create_ring_sysfs(), which is the only function which references vmbus_channel->mmap_prepare_ring_buffer which, in turn, is the only external interface to hv_mmap_prepare_ring_buffer. This patch therefore updates this caller to use mmap_prepare instead, which also previously used vm_iomap_memory(), so this change replaces it with its mmap_prepare equivalent, mmap_action_simple_ioremap(). [akpm@linux-foundation.org: restore struct vmbus_channel comment, per Michael Kelley] Link: https://lkml.kernel.org/r/05467cb62267d750e5c770147517d4df0246cda6.1774045440.git.ljs@kernel.org Signed-off-by: Lorenzo Stoakes (Oracle) Reviewed-by: Michael Kelley Tested-by: Michael Kelley Acked-by: Vlastimil Babka (SUSE) Cc: Alexander Shishkin Cc: Alexandre Torgue Cc: Al Viro Cc: Arnd Bergmann Cc: Bodo Stroesser Cc: Christian Brauner Cc: Clemens Ladisch Cc: David Hildenbrand Cc: David Howells Cc: Dexuan Cui Cc: Greg Kroah-Hartman Cc: Haiyang Zhang Cc: Jan Kara Cc: Jann Horn Cc: Jonathan Corbet Cc: K. Y. Srinivasan Cc: Liam Howlett Cc: Long Li Cc: Marc Dionne Cc: "Martin K. Petersen" Cc: Maxime Coquelin Cc: Michal Hocko Cc: Mike Rapoport Cc: Miquel Raynal Cc: Pedro Falcato Cc: Richard Weinberger Cc: Ryan Roberts Cc: Suren Baghdasaryan Cc: Vignesh Raghavendra Cc: Wei Liu Signed-off-by: Andrew Morton

mshv: Use try_cmpxchg() instead of cmpxchg()

2026-02-18T23:27:20+00:00

Use !try_cmpxchg() instead of cmpxchg (*ptr, old, new) != old. x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after CMPXCHG. The generated assembly code improves from e.g.: 415: 48 8b 44 24 30 mov 0x30(%rsp),%rax 41a: 48 8b 54 24 38 mov 0x38(%rsp),%rdx 41f: f0 49 0f b1 91 a8 02 lock cmpxchg %rdx,0x2a8(%r9) 426: 00 00 428: 48 3b 44 24 30 cmp 0x30(%rsp),%rax 42d: 0f 84 09 ff ff ff je 33c <...> to: 415: 48 8b 44 24 30 mov 0x30(%rsp),%rax 41a: 48 8b 54 24 38 mov 0x38(%rsp),%rdx 41f: f0 49 0f b1 91 a8 02 lock cmpxchg %rdx,0x2a8(%r9) 426: 00 00 428: 0f 84 0e ff ff ff je 33c <...> No functional change intended. Signed-off-by: Uros Bizjak Cc: K. Y. Srinivasan Cc: Haiyang Zhang Cc: Wei Liu Cc: Dexuan Cui Cc: Long Li Signed-off-by: Wei Liu

Drivers: hv: vmbus: fix typo in function name reference

2026-01-15T07:00:13+00:00

Replace cmxchg by cmpxchg. Signed-off-by: Julia Lawall Reviewed-by: Roman Kisel Signed-off-by: Wei Liu

Drivers: hv: Export some symbols for mshv_vtl

2025-11-15T06:18:17+00:00

MSHV_VTL driver is going to be introduced, which is supposed to provide interface for Virtual Machine Monitors (VMMs) to control Virtual Trust Level (VTL). Export the symbols needed to make it work (vmbus_isr, hv_context and hv_post_message). Co-developed-by: Roman Kisel Signed-off-by: Roman Kisel Co-developed-by: Saurabh Sengar Signed-off-by: Saurabh Sengar Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202506110544.q0NDMQVc-lkp@intel.com/ Reviewed-by: Michael Kelley Signed-off-by: Naman Jain Signed-off-by: Wei Liu

Drivers: hv: Allocate encrypted buffers when requested

2025-11-15T06:18:15+00:00

Confidential VMBus is built around using buffers not shared with the host. Support allocating encrypted buffers when requested. Signed-off-by: Roman Kisel Reviewed-by: Tianyu Lan Reviewed-by: Michael Kelley Signed-off-by: Wei Liu

Drivers: hv: Rename the SynIC enable and disable routines

2025-11-15T06:18:15+00:00

The confidential VMBus requires support for the both hypervisor facing SynIC and the paravisor one. Rename the functions that enable and disable SynIC with the hypervisor. No functional changes. Signed-off-by: Roman Kisel Reviewed-by: Tianyu Lan Reviewed-by: Michael Kelley Signed-off-by: Wei Liu

Drivers: hv: Allocate the paravisor SynIC pages when required

2025-11-15T06:18:15+00:00

Confidential VMBus requires interacting with two SynICs -- one provided by the host hypervisor, and one provided by the paravisor. Each SynIC requires its own message and event pages. Refactor and extend the existing code to add allocating and freeing the message and event pages for the paravisor SynIC when it is present. Signed-off-by: Roman Kisel Reviewed-by: Tianyu Lan Reviewed-by: Michael Kelley Signed-off-by: Wei Liu