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, 50 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-block-loop b/Documentation/ABI/testing/sysfs-block-loop
new file mode 100644
index 000000000..627f4eb87
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-block-loop
@@ -0,0 +1,50 @@
+What:		/sys/block/loopX/loop/autoclear
+Date:		Aug, 2010
+KernelVersion:	v2.6.37
+Contact:	linux-block@vger.kernel.org
+Description:
+		(RO) Shows if the device is in autoclear mode or not ( "1" or
+		"0"). Autoclear (if set) indicates that the loopback device will
+		self-distruct after last close.
+
+What:		/sys/block/loopX/loop/backing_file
+Date:		Aug, 2010
+KernelVersion:	v2.6.37
+Contact:	linux-block@vger.kernel.org
+Description:
+		(RO) The path of the backing file that the loop device maps its
+		data blocks to.
+
+What:		/sys/block/loopX/loop/offset
+Date:		Aug, 2010
+KernelVersion:	v2.6.37
+Contact:	linux-block@vger.kernel.org
+Description:
+		(RO) Start offset (in bytes).
+
+What:		/sys/block/loopX/loop/sizelimit
+Date:		Aug, 2010
+KernelVersion:	v2.6.37
+Contact:	linux-block@vger.kernel.org
+Description:
+		(RO) The size (in bytes) that the block device maps, starting
+		from the offset.
+
+What:		/sys/block/loopX/loop/partscan
+Date:		Aug, 2011
+KernelVersion:	v3.10
+Contact:	linux-block@vger.kernel.org
+Description:
+		(RO) Shows if automatic partition scanning is enabled for the
+		device or not ("1" or "0"). This can be requested individually
+		per loop device during its setup by setting LO_FLAGS_PARTSCAN in
+		in the ioctl request. By default, no partition tables are
+		scanned.
+
+What:		/sys/block/loopX/loop/dio
+Date:		Aug, 2015
+KernelVersion:	v4.10
+Contact:	linux-block@vger.kernel.org
+Description:
+		(RO) Shows if direct IO is being used to access backing file or
+		not ("1 or "0").