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, 40 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-kernel-reboot b/Documentation/ABI/testing/sysfs-kernel-reboot
new file mode 100644
index 000000000..52571fd5d
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-reboot
@@ -0,0 +1,40 @@
+What:		/sys/kernel/reboot
+Date:		November 2020
+KernelVersion:	5.11
+Contact:	Matteo Croce <teknoraver@meta.com>
+Description:	Interface to set the kernel reboot behavior, similarly to
+		what can be done via the reboot= cmdline option.
+		(see Documentation/admin-guide/kernel-parameters.txt)
+
+What:		/sys/kernel/reboot/mode
+Date:		November 2020
+KernelVersion:	5.11
+Contact:	Matteo Croce <teknoraver@meta.com>
+Description:	Reboot mode. Valid values are: cold warm hard soft gpio
+
+What:		/sys/kernel/reboot/type
+Date:		November 2020
+KernelVersion:	5.11
+Contact:	Matteo Croce <teknoraver@meta.com>
+Description:	Reboot type. Valid values are: bios acpi kbd triple efi pci
+
+What:		/sys/kernel/reboot/cpu
+Date:		November 2020
+KernelVersion:	5.11
+Contact:	Matteo Croce <teknoraver@meta.com>
+Description:	CPU number to use to reboot.
+
+What:		/sys/kernel/reboot/force
+Date:		November 2020
+KernelVersion:	5.11
+Contact:	Matteo Croce <teknoraver@meta.com>
+Description:	Don't wait for any other CPUs on reboot and
+		avoid anything that could hang.
+
+What:		/sys/kernel/reboot/hw_protection
+Date:		April 2025
+KernelVersion:	6.15
+Contact:	Ahmad Fatoum <a.fatoum@pengutronix.de>
+Description:	Hardware protection action taken on critical events like
+		overtemperature or imminent voltage loss.
+		Valid values are: reboot shutdown