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, 41 insertions, 0 deletions

diff --git a/arch/mips/kvm/Kconfig b/arch/mips/kvm/Kconfig
new file mode 100644
index 000000000..b1b9a1d67
--- /dev/null
+++ b/arch/mips/kvm/Kconfig
@@ -0,0 +1,41 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# KVM configuration
+#
+source "virt/kvm/Kconfig"
+
+menuconfig VIRTUALIZATION
+	bool "Virtualization"
+	help
+	  Say Y here to get to see options for using your Linux host to run
+	  other operating systems inside virtual machines (guests).
+	  This option alone does not add any kernel code.
+
+	  If you say N, all options in this submenu will be skipped and disabled.
+
+if VIRTUALIZATION
+
+config KVM
+	tristate "Kernel-based Virtual Machine (KVM) support"
+	depends on CPU_SUPPORTS_VZ
+	depends on MIPS_FP_SUPPORT
+	select EXPORT_UASM
+	select KVM_COMMON
+	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
+	select KVM_MMIO
+	select KVM_GENERIC_HARDWARE_ENABLING
+	select HAVE_KVM_READONLY_MEM
+	help
+	  Support for hosting Guest kernels.
+
+config KVM_MIPS_DEBUG_COP0_COUNTERS
+	bool "Maintain counters for COP0 accesses"
+	depends on KVM
+	help
+	  Maintain statistics for Guest COP0 accesses.
+	  A histogram of COP0 accesses is printed when the VM is
+	  shutdown.
+
+	  If unsure, say N.
+
+endif # VIRTUALIZATION