linux.git/drivers/hv, branch v7.2 Linux kernel source tree mshv_vtl: bounds-check cpu index in vtl mmap fault handler 2026-07-31T20:02:04+00:00 Yi Xie xieyi@kylinos.cn 2026-07-09T02:19:47+00:00 22dfdc17ceadd2783a609947af621a7f697b7765 cpu is taken from pgoff & 0xffff. cpu_online() does not reject cpu >= nr_cpu_ids, and per_cpu_ptr() can then walk off __per_cpu_offset. Signed-off-by: Yi Xie <xieyi@kylinos.cn> Reviewed-by: Naman Jain <namjain@linux.microsoft.com> Signed-off-by: Wei Liu <wei.liu@kernel.org> 
cpu is taken from pgoff & 0xffff.  cpu_online() does not reject cpu >=
nr_cpu_ids, and per_cpu_ptr() can then walk off __per_cpu_offset.

Signed-off-by: Yi Xie <xieyi@kylinos.cn>
Reviewed-by: Naman Jain <namjain@linux.microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
mshv: Publish VP to pt_vp_array before installing the file descriptor 2026-07-31T20:02:03+00:00 Stanislav Kinsburskii skinsburskii@linux.microsoft.com 2026-05-07T15:44:32+00:00 72e3b0311aa90568a4b42a64445d1d3e1dc5a34d mshv_partition_ioctl_create_vp() called anon_inode_getfd() before publishing the new VP into partition->pt_vp_array. anon_inode_getfd() includes fd_install(), so the fd was live in current->files before the publish ran. A concurrent MSHV_RUN_VP ioctl on that fd does not serialise against the in-progress MSHV_CREATE_VP — it takes vp->vp_mutex, not the partition mutex. Once the VP starts running and traps, mshv_intercept_isr() can look up partition->pt_vp_array[vp_index] and observe NULL, silently dropping the intercept message. Split the fd creation: reserve an fd with get_unused_fd_flags(), create the file with anon_inode_getfile(), publish the VP via smp_store_release(), and finally call fd_install() as the userspace-visibility commit point. Fixes: 621191d709b14 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs") Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com> Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com> Signed-off-by: Wei Liu <wei.liu@kernel.org> 
mshv_partition_ioctl_create_vp() called anon_inode_getfd() before
publishing the new VP into partition->pt_vp_array.  anon_inode_getfd()
includes fd_install(), so the fd was live in current->files before the
publish ran.

A concurrent MSHV_RUN_VP ioctl on that fd does not serialise against the
in-progress MSHV_CREATE_VP — it takes vp->vp_mutex, not the partition
mutex.  Once the VP starts running and traps, mshv_intercept_isr() can look
up partition->pt_vp_array[vp_index] and observe NULL, silently dropping the
intercept message.

Split the fd creation: reserve an fd with get_unused_fd_flags(), create the
file with anon_inode_getfile(), publish the VP via smp_store_release(), and
finally call fd_install() as the userspace-visibility commit point.

Fixes: 621191d709b14 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs")
Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Drivers: hv: vmbus: add VTL2 redirect connection ID 2026-07-31T20:02:03+00:00 Hardik Garg hargar@linux.microsoft.com 2026-07-17T00:18:37+00:00 92d0593128023cf93ae61b7728dcc3062f8d514f VMBus sends CHANNELMSG_INITIATE_CONTACT through a Hyper-V message connection ID. Older protocol versions use VMBUS_MESSAGE_CONNECTION_ID, while protocol version 5.0 and newer normally use VMBUS_MESSAGE_CONNECTION_ID_4. For a VTL2 kernel using VMBus protocol 5.0 or newer, the host may expect INITIATE_CONTACT on either the redirect connection ID or VMBUS_MESSAGE_CONNECTION_ID_4. There is no capability indication that identifies which ID is active, so the driver must determine it at runtime. During VMBus negotiation, the redirect ID is tried first because it is used by VTL2 configurations with VMBus redirection enabled. If the redirect ID is unavailable, the host rejects it synchronously with HV_STATUS_INVALID_CONNECTION_ID, allowing fallback to the standard ID. Return a distinct error for an invalid Initiate Contact connection ID so this fallback does not mask other post-message failures or protocol-version rejections. Preserve the existing connection ID selection for older protocol versions or when running below VTL2. Signed-off-by: Hardik Garg <hargar@linux.microsoft.com> Reviewed-by: Tianyu Lan <Tianyu.Lan@microsoft.com> Reviewed-by: Saurabh Sengar <ssengar@linux.microsoft.com> Reviewed-by: Naman Jain <namjain@linux.microsoft.com> Reviewed-by: Michael Kelley <mhklinux@outlook.com> Signed-off-by: Wei Liu <wei.liu@kernel.org> 
VMBus sends CHANNELMSG_INITIATE_CONTACT through a Hyper-V message
connection ID. Older protocol versions use VMBUS_MESSAGE_CONNECTION_ID,
while protocol version 5.0 and newer normally use
VMBUS_MESSAGE_CONNECTION_ID_4.

For a VTL2 kernel using VMBus protocol 5.0 or newer, the host
may expect INITIATE_CONTACT on either the redirect connection ID or
VMBUS_MESSAGE_CONNECTION_ID_4. There is no capability indication that
identifies which ID is active, so the driver must determine it at runtime.

During VMBus negotiation, the redirect ID is tried first because it is
used by VTL2 configurations with VMBus redirection enabled. If the
redirect ID is unavailable, the host rejects it synchronously with
HV_STATUS_INVALID_CONNECTION_ID, allowing fallback to the standard ID.

Return a distinct error for an invalid Initiate Contact connection ID so
this fallback does not mask other post-message failures or
protocol-version rejections. Preserve the existing connection ID
selection for older protocol versions or when running below VTL2.

Signed-off-by: Hardik Garg <hargar@linux.microsoft.com>
Reviewed-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
Reviewed-by: Saurabh Sengar <ssengar@linux.microsoft.com>
Reviewed-by: Naman Jain <namjain@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
mshv: Order pt_vp_array publish against irqfd assertion path 2026-07-31T20:01:59+00:00 Stanislav Kinsburskii skinsburskii@linux.microsoft.com 2026-07-23T00:28:11+00:00 b098dc869219c15dc49bf9cf63fb5fc1481d3373 mshv_partition_ioctl_create_vp() initialises a VP struct (allocations, mutex_init, init_waitqueue_head, page mappings) and then publishes the pointer into partition->pt_vp_array. Several ISR paths read this array locklessly: the intercept ISR, the two scheduler ISRs, and mshv_try_assert_irq_fast() on the irqfd fast path. Of these, only mshv_try_assert_irq_fast() can structurally race the publish. It runs from an eventfd waker without holding pt_mutex, and MSHV_IRQFD does not require the target lapic_apic_id (== vp_index) to refer to an existing VP at registration time. A user can therefore register an irqfd targeting a yet-to-be-created VP, then trigger mshv_try_assert_irq_fast() concurrently with MSHV_CREATE_VP for the same index. On weakly-ordered architectures the reader can observe a non-NULL pointer in pt_vp_array before the initialising stores to the VP struct become visible, leading to use of partially-initialised fields (e.g. vp_register_page). The other ISR readers cannot reach this race: the hypervisor will not generate intercept or scheduler messages for a VP that has never been told to run, and the user can only call MSHV_RUN_VP on the VP fd returned by MSHV_CREATE_VP, which by construction is returned after the publish. Leave those readers as plain loads. Use smp_store_release() in mshv_partition_ioctl_create_vp() to publish the pointer, and pair it with smp_load_acquire() in mshv_try_assert_irq_fast(). On x86 these compile to plain accesses under TSO; on ARM64 they emit one-instruction acquire/release barriers, acceptable on this fast path. The destroy-side path (destroy_partition() clearing pt_vp_array[i] to NULL after kfree(vp)) has a separate ordering and lifetime concern that is out of scope here. Fixes: 621191d709b14 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs") Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com> Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com> Signed-off-by: Wei Liu <wei.liu@kernel.org> 
mshv_partition_ioctl_create_vp() initialises a VP struct (allocations,
mutex_init, init_waitqueue_head, page mappings) and then publishes the
pointer into partition->pt_vp_array.  Several ISR paths read this array
locklessly: the intercept ISR, the two scheduler ISRs, and
mshv_try_assert_irq_fast() on the irqfd fast path.

Of these, only mshv_try_assert_irq_fast() can structurally race the
publish.  It runs from an eventfd waker without holding pt_mutex, and
MSHV_IRQFD does not require the target lapic_apic_id (== vp_index) to
refer to an existing VP at registration time.  A user can therefore
register an irqfd targeting a yet-to-be-created VP, then trigger
mshv_try_assert_irq_fast() concurrently with MSHV_CREATE_VP for the
same index.  On weakly-ordered architectures the reader can observe a
non-NULL pointer in pt_vp_array before the initialising stores to the
VP struct become visible, leading to use of partially-initialised
fields (e.g. vp_register_page).

The other ISR readers cannot reach this race: the hypervisor will not
generate intercept or scheduler messages for a VP that has never been
told to run, and the user can only call MSHV_RUN_VP on the VP fd
returned by MSHV_CREATE_VP, which by construction is returned after
the publish.  Leave those readers as plain loads.

Use smp_store_release() in mshv_partition_ioctl_create_vp() to publish
the pointer, and pair it with smp_load_acquire() in
mshv_try_assert_irq_fast().  On x86 these compile to plain accesses
under TSO; on ARM64 they emit one-instruction acquire/release barriers,
acceptable on this fast path.

The destroy-side path (destroy_partition() clearing pt_vp_array[i] to
NULL after kfree(vp)) has a separate ordering and lifetime concern
that is out of scope here.

Fixes: 621191d709b14 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs")
Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
mshv: Fix missing error code on VP allocation failure 2026-07-31T20:01:57+00:00 Stanislav Kinsburskii skinsburskii@linux.microsoft.com 2026-05-07T15:44:37+00:00 f546be6a19d24d02be576d8617cb26c7acb61594 In mshv_partition_ioctl_create_vp(), when kzalloc for the VP struct fails, the code jumps to the cleanup path without setting ret. At that point ret is 0 from the preceding successful mshv_vp_stats_map() call, so the function returns success to userspace despite having failed to create the VP. No fd is installed and no VP is registered in pt_vp_array, but userspace has no way to know the operation failed. Set ret to -ENOMEM before jumping to the cleanup path. Fixes: 621191d709b14 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs") Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com> Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com> Signed-off-by: Wei Liu <wei.liu@kernel.org> 
In mshv_partition_ioctl_create_vp(), when kzalloc for the VP struct
fails, the code jumps to the cleanup path without setting ret. At that
point ret is 0 from the preceding successful mshv_vp_stats_map() call,
so the function returns success to userspace despite having failed to
create the VP. No fd is installed and no VP is registered in pt_vp_array,
but userspace has no way to know the operation failed.

Set ret to -ENOMEM before jumping to the cleanup path.

Fixes: 621191d709b14 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs")
Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
mshv: Fix level-triggered check on uninitialized data 2026-07-31T20:01:57+00:00 Stanislav Kinsburskii skinsburskii@linux.microsoft.com 2026-05-07T15:43:43+00:00 0289a67cd70bf9d3807e289f4efd643e16a6c6b4 In mshv_irqfd_assign(), the level-triggered validation for resample irqfds checks irqfd_lapic_irq.lapic_control.level_triggered before mshv_irqfd_update() has populated the field. Since the irqfd struct is zero-allocated, level_triggered is always 0 at that point, causing the check to always reject resample irqfds with -EINVAL. This makes level-triggered interrupt resampling — used to avoid interrupt storms with assigned devices — completely non-functional. Move the check after the mshv_irqfd_update() call, which resolves the IRQ routing entry and populates irqfd_lapic_irq with the actual trigger mode. Fixes: 621191d709b14 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs") Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com> Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com> Signed-off-by: Wei Liu <wei.liu@kernel.org> 
In mshv_irqfd_assign(), the level-triggered validation for resample
irqfds checks irqfd_lapic_irq.lapic_control.level_triggered before
mshv_irqfd_update() has populated the field. Since the irqfd struct is
zero-allocated, level_triggered is always 0 at that point, causing the
check to always reject resample irqfds with -EINVAL. This makes
level-triggered interrupt resampling — used to avoid interrupt storms
with assigned devices — completely non-functional.

Move the check after the mshv_irqfd_update() call, which resolves the
IRQ routing entry and populates irqfd_lapic_irq with the actual trigger
mode.

Fixes: 621191d709b14 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs")
Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
mshv: Fix race in mshv_irqfd_deassign 2026-07-31T20:01:56+00:00 Stanislav Kinsburskii skinsburskii@linux.microsoft.com 2026-05-07T15:43:15+00:00 0762262ac3e70f65b3bb843fe892f8bac1562d08 mshv_irqfd_deactivate() and the hlist traversal of pt_irqfds_list require pt->pt_irqfds_lock to be held, but mshv_irqfd_deassign() omits it. This races with the EPOLLHUP path in mshv_irqfd_wakeup(), which does take the lock before calling mshv_irqfd_deactivate(). Additionally, mshv_irqfd_deactivate() uses hlist_del() which poisons the node pointers rather than resetting them. Since mshv_irqfd_is_active() relies on hlist_unhashed() (checks pprev == NULL), a poisoned node still appears active. If a concurrent path calls mshv_irqfd_deactivate() again on the same irqfd, the guard fails to prevent a double hlist_del() on poisoned pointers. Fix both issues: - Add the missing spin_lock_irq/spin_unlock_irq around the list traversal in mshv_irqfd_deassign(), matching mshv_irqfd_release(). - Use hlist_del_init() instead of hlist_del() so the node is properly marked as unhashed after removal, making the is_active guard reliable. Fixes: 621191d709b14 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs") Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com> Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com> Signed-off-by: Wei Liu <wei.liu@kernel.org> 
mshv_irqfd_deactivate() and the hlist traversal of pt_irqfds_list
require pt->pt_irqfds_lock to be held, but mshv_irqfd_deassign()
omits it. This races with the EPOLLHUP path in mshv_irqfd_wakeup(),
which does take the lock before calling mshv_irqfd_deactivate().

Additionally, mshv_irqfd_deactivate() uses hlist_del() which poisons
the node pointers rather than resetting them. Since
mshv_irqfd_is_active() relies on hlist_unhashed() (checks pprev ==
NULL), a poisoned node still appears active. If a concurrent path calls
mshv_irqfd_deactivate() again on the same irqfd, the guard fails to
prevent a double hlist_del() on poisoned pointers.

Fix both issues:
- Add the missing spin_lock_irq/spin_unlock_irq around the list
  traversal in mshv_irqfd_deassign(), matching mshv_irqfd_release().
- Use hlist_del_init() instead of hlist_del() so the node is properly
  marked as unhashed after removal, making the is_active guard reliable.

Fixes: 621191d709b14 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs")
Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
mshv: Use kfree_rcu in mshv_portid_free 2026-07-31T20:01:43+00:00 Stanislav Kinsburskii skinsburskii@linux.microsoft.com 2026-07-22T23:56:46+00:00 5cb5c2f4a8373eb4c8fdbfdc857bb28f28f71fe0 mshv_portid_free() uses synchronize_rcu() followed by kfree() to reclaim port table entries. This blocks the caller until a full RCU grace period elapses, which is unnecessary since the same module already uses the non-blocking kfree_rcu() pattern in mshv_port_table_fini(). Replace with kfree_rcu() to avoid the blocking wait and keep the reclamation strategy consistent across the file. Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com> Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com> Signed-off-by: Wei Liu <wei.liu@kernel.org> 
mshv_portid_free() uses synchronize_rcu() followed by kfree() to
reclaim port table entries. This blocks the caller until a full RCU
grace period elapses, which is unnecessary since the same module already
uses the non-blocking kfree_rcu() pattern in mshv_port_table_fini().

Replace with kfree_rcu() to avoid the blocking wait and keep the
reclamation strategy consistent across the file.

Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
mshv: Fix sleeping under spinlock in mshv_portid_alloc 2026-07-22T23:51:30+00:00 Stanislav Kinsburskii skinsburskii@linux.microsoft.com 2026-05-07T15:43:59+00:00 a9708e550d11a53b22d932cdbfaa10c26346a2d0 idr_alloc() is called with GFP_KERNEL inside idr_lock(), which holds a spinlock. GFP_KERNEL allows the allocator to sleep, triggering a sleeping-while-atomic bug. Fix by using idr_preload(GFP_KERNEL) before taking the lock to pre-allocate memory in a sleepable context, then idr_alloc() with GFP_NOWAIT inside the spinlock-protected section. Fixes: 621191d709b1 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs") Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com> Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com> Signed-off-by: Wei Liu <wei.liu@kernel.org> 
idr_alloc() is called with GFP_KERNEL inside idr_lock(), which holds a
spinlock. GFP_KERNEL allows the allocator to sleep, triggering a
sleeping-while-atomic bug.

Fix by using idr_preload(GFP_KERNEL) before taking the lock to
pre-allocate memory in a sleepable context, then idr_alloc() with
GFP_NOWAIT inside the spinlock-protected section.

Fixes: 621191d709b1 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs")
Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
mshv: Fix duplicate GSI detection for GSI 0 2026-07-22T23:51:25+00:00 Stanislav Kinsburskii skinsburskii@linux.microsoft.com 2026-05-07T15:43:49+00:00 649dd135491945afa544351e3e6d4a727de87020 The duplicate routing entry check in mshv_update_routing_table() uses guest_irq_num != 0 to detect whether a GSI slot is already occupied. This fails for GSI 0 because its guest_irq_num is 0 both when the slot is unused (zero-initialized) and when legitimately assigned. As a result, duplicate entries for GSI 0 are silently accepted, with the second entry overwriting the first — corrupting the routing table without any error reported to userspace. While GSI 0 (legacy timer) is unlikely to appear in MSI-based routing in practice, the check is semantically wrong — it conflates "uninitialized" with "GSI number 0." Use girq_entry_valid instead, which is explicitly set to true when an entry is populated and remains zero for unused slots regardless of the GSI number. Fixes: 621191d709b14 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs") Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com> Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com> Signed-off-by: Wei Liu <wei.liu@kernel.org> 
The duplicate routing entry check in mshv_update_routing_table() uses
guest_irq_num != 0 to detect whether a GSI slot is already occupied.
This fails for GSI 0 because its guest_irq_num is 0 both when the slot
is unused (zero-initialized) and when legitimately assigned. As a
result, duplicate entries for GSI 0 are silently accepted, with the
second entry overwriting the first — corrupting the routing table
without any error reported to userspace.

While GSI 0 (legacy timer) is unlikely to appear in MSI-based routing
in practice, the check is semantically wrong — it conflates
"uninitialized" with "GSI number 0." Use girq_entry_valid instead,
which is explicitly set to true when an entry is populated and remains
zero for unused slots regardless of the GSI number.

Fixes: 621191d709b14 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs")
Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@anirudhrb.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>