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, 49 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-driver-xdata b/Documentation/ABI/testing/sysfs-driver-xdata
new file mode 100644
index 000000000..f574e8e6d
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-xdata
@@ -0,0 +1,49 @@
+What:		/sys/class/misc/drivers/dw-xdata-pcie.<device>/write
+Date:		April 2021
+KernelVersion:	5.13
+Contact:	Gustavo Pimentel <gustavo.pimentel@synopsys.com>
+Description:	Allows the user to enable the PCIe traffic generator which
+		will create write TLPs frames - from the Root Complex to the
+		Endpoint direction or to disable the PCIe traffic generator
+		in all directions.
+
+		Write y/1/on to enable, n/0/off to disable
+
+		Usage e.g.
+		 echo 1 > /sys/class/misc/dw-xdata-pcie.<device>/write
+		or
+		 echo 0 > /sys/class/misc/dw-xdata-pcie.<device>/write
+
+		The user can read the current PCIe link throughput generated
+		through this generator in MB/s.
+
+		Usage e.g.
+		 cat /sys/class/misc/dw-xdata-pcie.<device>/write
+		 204
+
+		The file is read and write.
+
+What:		/sys/class/misc/dw-xdata-pcie.<device>/read
+Date:		April 2021
+KernelVersion:	5.13
+Contact:	Gustavo Pimentel <gustavo.pimentel@synopsys.com>
+Description:	Allows the user to enable the PCIe traffic generator which
+		will create read TLPs frames - from the Endpoint to the Root
+		Complex direction or to disable the PCIe traffic generator
+                in all directions.
+
+		Write y/1/on to enable, n/0/off to disable
+
+		Usage e.g.
+		 echo 1 > /sys/class/misc/dw-xdata-pcie.<device>/read
+		or
+		 echo 0 > /sys/class/misc/dw-xdata-pcie.<device>/read
+
+		The user can read the current PCIe link throughput generated
+		through this generator in MB/s.
+
+		Usage e.g.
+		 cat /sys/class/misc/dw-xdata-pcie.<device>/read
+		 199
+
+		The file is read and write.