kernel/linux.git/drivers/hv, branch v6.18.36

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

2026-06-19T11:43:56+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 protocol version 6.0

2026-06-19T11:43:55+00:00

[ Upstream commit 6802d8af47d1dccd9a74a1f708fb9129244ef843 ] The confidential VMBus is supported starting from the protocol version 6.0 onwards. Provide the required definitions. No functional changes. Signed-off-by: Roman Kisel Reviewed-by: Alok Tiwari Reviewed-by: Michael Kelley Signed-off-by: Wei Liu Stable-dep-of: c5c3ef8d49e1 ("Drivers: hv: vmbus: Provide option to skip VMBus unload on panic") Signed-off-by: Sasha Levin

hv: Select CONFIG_SYSFB only for CONFIG_HYPERV_VMBUS

2026-05-14T13:30:17+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: clear eventfd counter on irqfd shutdown

2026-03-04T12:20:39+00:00

[ Upstream commit 2b4246153e2184e3a3b4edc8cc35337d7a2455a6 ] While unhooking from the irqfd waitqueue, clear the internal eventfd counter by using eventfd_ctx_remove_wait_queue() instead of remove_wait_queue(), preventing potential spurious interrupts. This removes the need to store a pointer into the workqueue, as the eventfd already keeps track of it. This mimicks what other similar subsystems do on their equivalent paths with their irqfds (KVM, Xen, ACRN support, etc). Signed-off-by: Carlos López Signed-off-by: Wei Liu Signed-off-by: Sasha Levin

Drivers: hv: vmbus: Use kthread for vmbus interrupts on PREEMPT_RT

2026-02-26T22:59:47+00:00

commit f8e6343b7a89c7c649db5a9e309ba7aa20401813 upstream. Resolves the following lockdep report when booting PREEMPT_RT on Hyper-V with related guest support enabled: [ 1.127941] hv_vmbus: registering driver hyperv_drm [ 1.132518] ============================= [ 1.132519] [ BUG: Invalid wait context ] [ 1.132521] 6.19.0-rc8+ #9 Not tainted [ 1.132524] ----------------------------- [ 1.132525] swapper/0/0 is trying to lock: [ 1.132526] ffff8b9381bb3c90 (&channel->sched_lock){....}-{3:3}, at: vmbus_chan_sched+0xc4/0x2b0 [ 1.132543] other info that might help us debug this: [ 1.132544] context-{2:2} [ 1.132545] 1 lock held by swapper/0/0: [ 1.132547] #0: ffffffffa010c4c0 (rcu_read_lock){....}-{1:3}, at: vmbus_chan_sched+0x31/0x2b0 [ 1.132557] stack backtrace: [ 1.132560] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.19.0-rc8+ #9 PREEMPT_{RT,(lazy)} [ 1.132565] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.1 09/25/2025 [ 1.132567] Call Trace: [ 1.132570] [ 1.132573] dump_stack_lvl+0x6e/0xa0 [ 1.132581] __lock_acquire+0xee0/0x21b0 [ 1.132592] lock_acquire+0xd5/0x2d0 [ 1.132598] ? vmbus_chan_sched+0xc4/0x2b0 [ 1.132606] ? lock_acquire+0xd5/0x2d0 [ 1.132613] ? vmbus_chan_sched+0x31/0x2b0 [ 1.132619] rt_spin_lock+0x3f/0x1f0 [ 1.132623] ? vmbus_chan_sched+0xc4/0x2b0 [ 1.132629] ? vmbus_chan_sched+0x31/0x2b0 [ 1.132634] vmbus_chan_sched+0xc4/0x2b0 [ 1.132641] vmbus_isr+0x2c/0x150 [ 1.132648] __sysvec_hyperv_callback+0x5f/0xa0 [ 1.132654] sysvec_hyperv_callback+0x88/0xb0 [ 1.132658] [ 1.132659] [ 1.132660] asm_sysvec_hyperv_callback+0x1a/0x20 As code paths that handle vmbus IRQs use sleepy locks under PREEMPT_RT, the vmbus_isr execution needs to be moved into thread context. Open- coding this allows to skip the IPI that irq_work would additionally bring and which we do not need, being an IRQ, never an NMI. This affects both x86 and arm64, therefore hook into the common driver logic. Signed-off-by: Jan Kiszka Reviewed-by: Florian Bezdeka Tested-by: Florian Bezdeka Reviewed-by: Michael Kelley Tested-by: Michael Kelley Signed-off-by: Wei Liu Signed-off-by: Greg Kroah-Hartman

mshv: fix SRCU protection in irqfd resampler ack handler

2026-02-26T22:59:42+00:00

[ Upstream commit 2e7577cd5ddc1f86d1b6c48caf3cfa87dbb14e34 ] Replace hlist_for_each_entry_rcu() with hlist_for_each_entry_srcu() in mshv_irqfd_resampler_ack() to correctly handle SRCU-protected linked list traversal. The function uses SRCU (sleepable RCU) synchronization via partition->pt_irq_srcu, but was incorrectly using the RCU variant for list iteration. This could lead to race conditions when the list is modified concurrently. Also add srcu_read_lock_held() assertion as required by hlist_for_each_entry_srcu() to ensure we're in the proper read-side critical section. Fixes: 621191d709b14 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs") Signed-off-by: Li RongQing Reviewed-by: Anirudh Rayabharam (Microsoft) Acked-by: Stanislav Kinsburskii Signed-off-by: Wei Liu Signed-off-by: Sasha Levin

Drivers: hv: Always do Hyper-V panic notification in hv_kmsg_dump()

2026-01-30T09:32:09+00:00

[ Upstream commit 49f49d47af67f8a7b221db1d758fc634242dc91a ] hv_kmsg_dump() currently skips the panic notification entirely if it doesn't get any message bytes to pass to Hyper-V due to an error from kmsg_dump_get_buffer(). Skipping the notification is undesirable because it leaves the Hyper-V host uncertain about the state of a panic'ed guest. Fix this by always doing the panic notification, even if bytes_written is zero. Also ensure that bytes_written is initialized, which fixes a kernel test robot warning. The warning is actually bogus because kmsg_dump_get_buffer() happens to set bytes_written even if it fails, and in the kernel test robot's CONFIG_PRINTK not set case, hv_kmsg_dump() is never called. But do the initialization for robustness and to quiet the static checker. Fixes: 9c318a1d9b50 ("Drivers: hv: move panic report code from vmbus to hv early init code") Reported-by: kernel test robot Reported-by: Dan Carpenter Closes: https://lore.kernel.org/all/202512172103.OcUspn1Z-lkp@intel.com/ Signed-off-by: Michael Kelley Reviewed-by: Roman Kisel Signed-off-by: Wei Liu Signed-off-by: Sasha Levin

mshv: Fix create memory region overlap check

2025-12-18T13:03:02+00:00

[ Upstream commit ba9eb9b86d232854e983203dc2fb1ba18e316681 ] The current check is incorrect; it only checks if the beginning or end of a region is within an existing region. This doesn't account for userspace specifying a region that begins before and ends after an existing region. Change the logic to a range intersection check against gfns and uaddrs for each region. Remove mshv_partition_region_by_uaddr() as it is no longer used. Fixes: 621191d709b1 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs") Reported-by: Michael Kelley Closes: https://lore.kernel.org/linux-hyperv/SN6PR02MB41575BE0406D3AB22E1D7DB5D4C2A@SN6PR02MB4157.namprd02.prod.outlook.com/ Signed-off-by: Nuno Das Neves Reviewed-by: Michael Kelley Signed-off-by: Wei Liu Signed-off-by: Sasha Levin

mshv: Fix deposit memory in MSHV_ROOT_HVCALL

2025-12-18T13:03:01+00:00

[ Upstream commit 4cc1aa469cd6b714adc958547a4866247bfd60a9 ] When the MSHV_ROOT_HVCALL ioctl is executing a hypercall, and gets HV_STATUS_INSUFFICIENT_MEMORY, it deposits memory and then returns -EAGAIN to userspace. The expectation is that the VMM will retry. However, some VMM code in the wild doesn't do this and simply fails. Rather than force the VMM to retry, change the ioctl to deposit memory on demand and immediately retry the hypercall as is done with all the other hypercall helper functions. In addition to making the ioctl easier to use, removing the need for multiple syscalls improves performance. There is a complication: unlike the other hypercall helper functions, in MSHV_ROOT_HVCALL the input is opaque to the kernel. This is problematic for rep hypercalls, because the next part of the input list can't be copied on each loop after depositing pages (this was the original reason for returning -EAGAIN in this case). Introduce hv_do_rep_hypercall_ex(), which adds a 'rep_start' parameter. This solves the issue, allowing the deposit loop in MSHV_ROOT_HVCALL to restart a rep hypercall after depositing pages partway through. Fixes: 621191d709b1 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs") Signed-off-by: Nuno Das Neves Reviewed-by: Michael Kelley Signed-off-by: Wei Liu Signed-off-by: Sasha Levin

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