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, 57 insertions, 0 deletions

diff --git a/arch/arm64/boot/Makefile b/arch/arm64/boot/Makefile
new file mode 100644
index 000000000..b5a08333b
--- /dev/null
+++ b/arch/arm64/boot/Makefile
@@ -0,0 +1,57 @@
+#
+# arch/arm64/boot/Makefile
+#
+# This file is included by the global makefile so that you can add your own
+# architecture-specific flags and dependencies.
+#
+# This file is subject to the terms and conditions of the GNU General Public
+# License.  See the file "COPYING" in the main directory of this archive
+# for more details.
+#
+# Copyright (C) 2012, ARM Ltd.
+# Author: Will Deacon <will.deacon@arm.com>
+#
+# Based on the ia64 boot/Makefile.
+#
+
+OBJCOPYFLAGS_Image :=-O binary -R .note -R .note.gnu.build-id -R .comment -S
+
+targets := Image Image.bz2 Image.gz Image.lz4 Image.lzma Image.lzo \
+	Image.zst Image.xz image.fit
+
+$(obj)/Image: vmlinux FORCE
+	$(call if_changed,objcopy)
+
+$(obj)/Image.bz2: $(obj)/Image FORCE
+	$(call if_changed,bzip2)
+
+$(obj)/Image.gz: $(obj)/Image FORCE
+	$(call if_changed,gzip)
+
+$(obj)/Image.lz4: $(obj)/Image FORCE
+	$(call if_changed,lz4)
+
+$(obj)/Image.lzma: $(obj)/Image FORCE
+	$(call if_changed,lzma)
+
+$(obj)/Image.lzo: $(obj)/Image FORCE
+	$(call if_changed,lzo)
+
+$(obj)/Image.zst: $(obj)/Image FORCE
+	$(call if_changed,zstd)
+
+$(obj)/Image.xz: $(obj)/Image FORCE
+	$(call if_changed,xzkern)
+
+$(obj)/image.fit: $(obj)/Image $(obj)/dts/dtbs-list FORCE
+	$(call if_changed,fit)
+
+EFI_ZBOOT_PAYLOAD	:= Image
+EFI_ZBOOT_BFD_TARGET	:= elf64-littleaarch64
+EFI_ZBOOT_MACH_TYPE	:= ARM64
+EFI_ZBOOT_FORWARD_CFI	:= $(CONFIG_ARM64_BTI_KERNEL)
+
+EFI_ZBOOT_OBJCOPY_FLAGS	= --add-symbol zboot_code_size=0x$$( \
+				$(NM) vmlinux|grep _kernel_codesize|cut -d' ' -f1)
+
+include $(srctree)/drivers/firmware/efi/libstub/Makefile.zboot