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, 34 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-spi-master b/Documentation/ABI/testing/sysfs-class-spi-master
new file mode 100644
index 000000000..0a524fcd9
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-spi-master
@@ -0,0 +1,34 @@
+What:		/sys/class/spi_master/spiB/new_device
+Date:		July 2026
+KernelVersion:	7.3
+Contact:	linux-spi@vger.kernel.org
+Description:	(WO) Instantiate a new SPI device on bus B, where B
+		is the bus number (0, 1, 2, ...). Takes parameters
+		in the format:
+
+		<modalias> <chip_select> [<max_speed_hz> [<mode>]]
+
+		where modalias is the driver name, chip_select is the
+		CS line number, and max_speed_hz and mode are optional.
+
+		The device can later be removed with delete_device.
+
+		Only devices created via this interface can be removed
+		with delete_device; platform and DT devices are not
+		affected.
+
+		Example:
+		# echo spidev 0 > /sys/class/spi_master/spi0/new_device
+		# echo spidev 0 10000000 > /sys/class/spi_master/spi0/new_device
+		# echo spidev 0 10000000 3 > /sys/class/spi_master/spi0/new_device
+
+What:		/sys/class/spi_master/spiB/delete_device
+Date:		July 2026
+KernelVersion:	7.3
+Contact:	linux-spi@vger.kernel.org
+Description:	(WO) Remove a SPI device previously created via
+		new_device. Takes a single parameter: the chip select
+		number of the device to remove.
+
+		Example:
+		# echo 0 > /sys/class/spi_master/spi0/delete_device