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/procfs-diskstats b/Documentation/ABI/testing/procfs-diskstats
new file mode 100644
index 000000000..6a719cf20
--- /dev/null
+++ b/Documentation/ABI/testing/procfs-diskstats
@@ -0,0 +1,43 @@
+What:		/proc/diskstats
+Date:		February 2008
+Contact:	Jerome Marchand <jmarchan@redhat.com>
+Description:
+		The /proc/diskstats file displays the I/O statistics
+		of block devices. Each line contains the following 14
+		fields:
+
+		==  ===================================
+		 1  major number
+		 2  minor number
+		 3  device name
+		 4  reads completed successfully
+		 5  reads merged
+		 6  sectors read
+		 7  time spent reading (ms)
+		 8  writes completed
+		 9  writes merged
+		10  sectors written
+		11  time spent writing (ms)
+		12  I/Os currently in progress
+		13  time spent doing I/Os (ms)
+		14  weighted time spent doing I/Os (ms)
+		==  ===================================
+
+		Kernel 4.18+ appends four more fields for discard
+		tracking putting the total at 18:
+
+		==  ===================================
+		15  discards completed successfully
+		16  discards merged
+		17  sectors discarded
+		18  time spent discarding
+		==  ===================================
+
+		Kernel 5.5+ appends two more fields for flush requests:
+
+		==  =====================================
+		19  flush requests completed successfully
+		20  time spent flushing
+		==  =====================================
+
+		For more details refer to Documentation/admin-guide/iostats.rst