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, 73 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-issei b/Documentation/ABI/testing/sysfs-class-issei
new file mode 100644
index 000000000..73a01f462
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-issei
@@ -0,0 +1,73 @@
+What:		/sys/class/issei/
+Date:		June 2026
+KernelVersion:	7.2
+Contact:	Alexander Usyskin <alexander.usyskin@intel.com>
+Description:
+		The issei/ class sub-directory belongs to issei device class
+
+What:		/sys/class/issei/issei<N>/
+Date:		June 2026
+KernelVersion:	7.2
+Contact:	Alexander Usyskin <alexander.usyskin@intel.com>
+Description:
+		The /sys/class/issei/isseiN directory is created for
+		each probed issei device
+
+What:		/sys/class/issei/issei<N>/fw_ver
+Date:		June 2026
+KernelVersion:	7.2
+Contact:	Alexander Usyskin <alexander.usyskin@intel.com>
+Description:	Display the ISSE firmware version.
+
+		The version of the ISSE firmware is in format:
+		<major>.<minor>.<milestone>.<build_no>.
+
+What:		/sys/class/issei/issei<N>/fw_clients
+Date:		June 2026
+KernelVersion:	7.2
+Contact:	Alexander Usyskin <alexander.usyskin@intel.com>
+Description:
+		The fw_clients directory stores all firmware clients on the
+		probed issei device
+
+What:		/sys/class/issei/issei<N>/fw_clients/<M>
+Date:		June 2026
+KernelVersion:	7.2
+Contact:	Alexander Usyskin <alexander.usyskin@intel.com>
+Description:
+		The /sys/class/issei/isseiN/fw_client/M directory is created for
+		each firmware client on the probed issei device where M is the
+		id of firmware client.
+
+What:		/sys/class/issei/issei<N>/fw_clients/<M>/id
+Date:		June 2026
+KernelVersion:	7.2
+Contact:	Alexander Usyskin <alexander.usyskin@intel.com>
+Description:    Displays id of the firmware client
+
+		The id of firmware client is it's number in client enumeration order,
+		starting from 1.
+
+What:		/sys/class/issei/issei<N>/fw_clients/<M>/uuid
+Date:		June 2026
+KernelVersion:	7.2
+Contact:	Alexander Usyskin <alexander.usyskin@intel.com>
+Description:    Displays uuid of the firmware client
+
+		The universally unique identifier of the firmware client
+
+What:		/sys/class/issei/issei<N>/fw_clients/<M>/mtu
+Date:		June 2026
+KernelVersion:	7.2
+Contact:	Alexander Usyskin <alexander.usyskin@intel.com>
+Description:    Displays maximum transmission unit of the firmware client
+
+		The maximum transmission unit (in bytes) used by the firmware client.
+
+What:		/sys/class/issei/issei<N>/fw_clients/<M>/ver
+Date:		June 2026
+KernelVersion:	7.2
+Contact:	Alexander Usyskin <alexander.usyskin@intel.com>
+Description:    Displays version of the firmware client
+
+		The version of the firmware client