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, 131 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/debugfs-amd-iommu b/Documentation/ABI/testing/debugfs-amd-iommu
new file mode 100644
index 000000000..5621a66aa
--- /dev/null
+++ b/Documentation/ABI/testing/debugfs-amd-iommu
@@ -0,0 +1,131 @@
+What:		/sys/kernel/debug/iommu/amd/iommu<x>/mmio
+Date:		January 2025
+Contact:	Dheeraj Kumar Srivastava <dheerajkumar.srivastava@amd.com>
+Description:
+		This file provides read/write access for user input. Users specify the
+		MMIO register offset for iommu<x>, and the file outputs the corresponding
+		MMIO register value of iommu<x>
+
+		Example::
+
+		  $ echo "0x18" > /sys/kernel/debug/iommu/amd/iommu00/mmio
+		  $ cat /sys/kernel/debug/iommu/amd/iommu00/mmio
+
+		Output::
+
+		  Offset:0x18 Value:0x000c22000003f48d
+
+What:		/sys/kernel/debug/iommu/amd/iommu<x>/capability
+Date:		January 2025
+Contact:	Dheeraj Kumar Srivastava <dheerajkumar.srivastava@amd.com>
+Description:
+		This file provides read/write access for user input. Users specify the
+		capability register offset for iommu<x>, and the file outputs the
+		corresponding capability register value of iommu<x>.
+
+		Example::
+
+		  $ echo "0x10" > /sys/kernel/debug/iommu/amd/iommu00/capability
+		  $ cat /sys/kernel/debug/iommu/amd/iommu00/capability
+
+		Output::
+
+		  Offset:0x10 Value:0x00203040
+
+What:		/sys/kernel/debug/iommu/amd/iommu<x>/cmdbuf
+Date:		January 2025
+Contact:	Dheeraj Kumar Srivastava <dheerajkumar.srivastava@amd.com>
+Description:
+		This file is a read-only output file containing iommu<x> command
+		buffer entries.
+
+		Examples::
+
+		  $ cat /sys/kernel/debug/iommu/amd/iommu<x>/cmdbuf
+
+		Output::
+
+		  CMD Buffer Head Offset:339 Tail Offset:339
+		    0: 00835001 10000001 00003c00 00000000
+		    1: 00000000 30000005 fffff003 7fffffff
+		    2: 00835001 10000001 00003c01 00000000
+		    3: 00000000 30000005 fffff003 7fffffff
+		    4: 00835001 10000001 00003c02 00000000
+		    5: 00000000 30000005 fffff003 7fffffff
+		    6: 00835001 10000001 00003c03 00000000
+		    7: 00000000 30000005 fffff003 7fffffff
+		    8: 00835001 10000001 00003c04 00000000
+		    9: 00000000 30000005 fffff003 7fffffff
+		   10: 00835001 10000001 00003c05 00000000
+		   11: 00000000 30000005 fffff003 7fffffff
+		  [...]
+
+What:		/sys/kernel/debug/iommu/amd/devid
+Date:		January 2025
+Contact:	Dheeraj Kumar Srivastava <dheerajkumar.srivastava@amd.com>
+Description:
+		This file provides read/write access for user input. Users specify the
+		device ID, which can be used to dump IOMMU data structures such as the
+		interrupt remapping table and device table.
+
+		Example:
+
+		1.
+		  ::
+
+		    $ echo 0000:01:00.0 > /sys/kernel/debug/iommu/amd/devid
+		    $ cat /sys/kernel/debug/iommu/amd/devid
+
+		  Output::
+
+		    0000:01:00.0
+
+		2.
+		  ::
+
+		    $ echo 01:00.0 > /sys/kernel/debug/iommu/amd/devid
+		    $ cat /sys/kernel/debug/iommu/amd/devid
+
+		  Output::
+
+		    0000:01:00.0
+
+What:		/sys/kernel/debug/iommu/amd/devtbl
+Date:		January 2025
+Contact:	Dheeraj Kumar Srivastava <dheerajkumar.srivastava@amd.com>
+Description:
+		This file is a read-only output file containing the device table entry
+		for the device ID provided in /sys/kernel/debug/iommu/amd/devid.
+
+		Example::
+
+		  $ cat /sys/kernel/debug/iommu/amd/devtbl
+
+		Output::
+
+		  DeviceId             QWORD[3]         QWORD[2]         QWORD[1]         QWORD[0] iommu
+		  0000:01:00.0 0000000000000000 20000001373b8013 0000000000000038 6000000114d7b603 iommu3
+
+What:		/sys/kernel/debug/iommu/amd/irqtbl
+Date:		January 2025
+Contact:	Dheeraj Kumar Srivastava <dheerajkumar.srivastava@amd.com>
+Description:
+		This file is a read-only output file containing valid IRT table entries
+		for the device ID provided in /sys/kernel/debug/iommu/amd/devid.
+
+		Example::
+
+		  $ cat /sys/kernel/debug/iommu/amd/irqtbl
+
+		Output::
+
+		  DeviceId 0000:01:00.0
+		  IRT[0000] 0000000000000020 0000000000000241
+		  IRT[0001] 0000000000000020 0000000000000841
+		  IRT[0002] 0000000000000020 0000000000002041
+		  IRT[0003] 0000000000000020 0000000000008041
+		  IRT[0004] 0000000000000020 0000000000020041
+		  IRT[0005] 0000000000000020 0000000000080041
+		  IRT[0006] 0000000000000020 0000000000200041
+		  IRT[0007] 0000000000000020 0000000000800041
+		  [...]