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, 91 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/debugfs-driver-genwqe b/Documentation/ABI/testing/debugfs-driver-genwqe
new file mode 100644
index 000000000..b45b01654
--- /dev/null
+++ b/Documentation/ABI/testing/debugfs-driver-genwqe
@@ -0,0 +1,91 @@
+What:           /sys/kernel/debug/genwqe/genwqe<n>_card/ddcb_info
+Date:           Oct 2013
+Contact:        haver@linux.vnet.ibm.com
+Description:    DDCB queue dump used for debugging queueing problems.
+
+What:           /sys/kernel/debug/genwqe/genwqe<n>_card/curr_regs
+Date:           Oct 2013
+Contact:        haver@linux.vnet.ibm.com
+Description:    Dump of the current error registers.
+                Only available for PF.
+
+What:           /sys/kernel/debug/genwqe/genwqe<n>_card/curr_dbg_uid0
+Date:           Oct 2013
+Contact:        haver@linux.vnet.ibm.com
+Description:    Internal chip state of UID0 (unit id 0).
+                Only available for PF.
+
+What:           /sys/kernel/debug/genwqe/genwqe<n>_card/curr_dbg_uid1
+Date:           Oct 2013
+Contact:        haver@linux.vnet.ibm.com
+Description:    Internal chip state of UID1.
+                Only available for PF.
+
+What:           /sys/kernel/debug/genwqe/genwqe<n>_card/curr_dbg_uid2
+Date:           Oct 2013
+Contact:        haver@linux.vnet.ibm.com
+Description:    Internal chip state of UID2.
+                Only available for PF.
+
+What:           /sys/kernel/debug/genwqe/genwqe<n>_card/prev_regs
+Date:           Oct 2013
+Contact:        haver@linux.vnet.ibm.com
+Description:    Dump of the error registers before the last reset of
+                the card occurred.
+                Only available for PF.
+
+What:           /sys/kernel/debug/genwqe/genwqe<n>_card/prev_dbg_uid0
+Date:           Oct 2013
+Contact:        haver@linux.vnet.ibm.com
+Description:    Internal chip state of UID0 before card was reset.
+                Only available for PF.
+
+What:           /sys/kernel/debug/genwqe/genwqe<n>_card/prev_dbg_uid1
+Date:           Oct 2013
+Contact:        haver@linux.vnet.ibm.com
+Description:    Internal chip state of UID1 before card was reset.
+                Only available for PF.
+
+What:           /sys/kernel/debug/genwqe/genwqe<n>_card/prev_dbg_uid2
+Date:           Oct 2013
+Contact:        haver@linux.vnet.ibm.com
+Description:    Internal chip state of UID2 before card was reset.
+                Only available for PF.
+
+What:           /sys/kernel/debug/genwqe/genwqe<n>_card/info
+Date:           Oct 2013
+Contact:        haver@linux.vnet.ibm.com
+Description:    Comprehensive summary of bitstream version and software
+                version. Used bitstream and bitstream clocking information.
+
+What:           /sys/kernel/debug/genwqe/genwqe<n>_card/err_inject
+Date:           Oct 2013
+Contact:        haver@linux.vnet.ibm.com
+Description:    Possibility to inject error cases to ensure that the drivers
+                error handling code works well.
+
+What:           /sys/kernel/debug/genwqe/genwqe<n>_card/vf<0..14>_jobtimeout_msec
+Date:           Oct 2013
+Contact:        haver@linux.vnet.ibm.com
+Description:    Default VF timeout 250ms. Testing might require 1000ms.
+                Using 0 will use the cards default value (whatever that is).
+
+                The timeout depends on the max number of available cards
+                in the system and the maximum allowed queue size.
+
+                The driver ensures that the settings are done just before
+                the VFs get enabled. Changing the timeouts in flight is not
+                possible.
+                Only available for PF.
+
+What:           /sys/kernel/debug/genwqe/genwqe<n>_card/jobtimer
+Date:           Oct 2013
+Contact:        haver@linux.vnet.ibm.com
+Description:    Dump job timeout register values for PF and VFs.
+                Only available for PF.
+
+What:           /sys/kernel/debug/genwqe/genwqe<n>_card/queue_working_time
+Date:           Dec 2013
+Contact:        haver@linux.vnet.ibm.com
+Description:    Dump queue working time register values for PF and VFs.
+                Only available for PF.