KVM: SEV: Do cache maintenance on the source VM during intra-host migrationgrafted

Manually perform cache maintenance on the source VM during intra-host
migration to ensure no stale data is left in CPU caches after the VM is
destroyed.  Because the source VM is "converted" to a non-SEV VM, KVM's
memory reclaim flows won't trigger cache maintenance, e.g. when all guest
memory is reclaimed in response to detaching from the mmu_notifier.

Note, relying on the destination VM to do cache maintenance isn't an option
as KVM doesn't require identical guest memory configurations, i.e. the
source VM may have access to memory that the destination VM does not.
Enforcing equivalent memory configurations is infeasible, as it would
require a *deep* comparison of memslots, e.g. to verify that not only are
the memslot identical, but what the memslots point at is also identical.

Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
Cc: stable@vger.kernel.org
Reported-by: Stefan Teodorescu <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260923163721.1584779-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/debugfs-hisi-migration b/Documentation/ABI/testing/debugfs-hisi-migration
new file mode 100644
index 000000000..2c01b2d38
--- /dev/null
+++ b/Documentation/ABI/testing/debugfs-hisi-migration
@@ -0,0 +1,25 @@
+What:		/sys/kernel/debug/vfio/<device>/migration/hisi_acc/dev_data
+Date:		Jan 2025
+KernelVersion:  6.13
+Contact:	Longfang Liu <liulongfang@huawei.com>
+Description:	Read the configuration data and some status data
+		required for device live migration. These data include device
+		status data, queue configuration data, some task configuration
+		data and device attribute data. The output format of the data
+		is defined by the live migration driver.
+
+What:		/sys/kernel/debug/vfio/<device>/migration/hisi_acc/migf_data
+Date:		Jan 2025
+KernelVersion:  6.13
+Contact:	Longfang Liu <liulongfang@huawei.com>
+Description:	Read the data from the last completed live migration.
+		This data includes the same device status data as in "dev_data".
+		The migf_data is the dev_data that is migrated.
+
+What:		/sys/kernel/debug/vfio/<device>/migration/hisi_acc/cmd_state
+Date:		Jan 2025
+KernelVersion:  6.13
+Contact:	Longfang Liu <liulongfang@huawei.com>
+Description:	Used to obtain the device command sending and receiving
+		channel status. Returns failure or success logs based on the
+		results.