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, 43 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-pps-gen b/Documentation/ABI/testing/sysfs-pps-gen
new file mode 100644
index 000000000..2519207b8
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-pps-gen
@@ -0,0 +1,43 @@
+What:		/sys/class/pps-gen/
+Date:		February 2025
+KernelVersion:  6.13
+Contact:	Rodolfo Giometti <giometti@enneenne.com>
+Description:
+		The /sys/class/pps-gen/ directory contains files and
+		directories that provide a unified interface to the PPS
+		generators.
+
+What:		/sys/class/pps-gen/pps-genX/
+Date:		February 2025
+KernelVersion:  6.13
+Contact:	Rodolfo Giometti <giometti@enneenne.com>
+Description:
+		The /sys/class/pps-gen/pps-genX/ directory is related to X-th
+		PPS generator in the system. Each directory contain files to
+		manage and control its PPS generator.
+
+What:		/sys/class/pps-gen/pps-genX/enable
+Date:		February 2025
+KernelVersion:  6.13
+Contact:	Rodolfo Giometti <giometti@enneenne.com>
+Description:
+		This write-only file enables or disables generation of the
+		PPS signal.
+
+What:		/sys/class/pps-gen/pps-genX/system
+Date:		February 2025
+KernelVersion:  6.13
+Contact:	Rodolfo Giometti <giometti@enneenne.com>
+Description:
+		This read-only file returns "1" if the generator takes the
+		timing from the system clock, while it returns "0" if not
+		(i.e. from a peripheral device clock).
+
+What:		/sys/class/pps-gen/pps-genX/time
+Date:		February 2025
+KernelVersion:  6.13
+Contact:	Rodolfo Giometti <giometti@enneenne.com>
+Description:
+		This read-only file contains the current time stored into the
+		generator clock as two integers representing the current time
+		seconds and nanoseconds.