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, 92 insertions, 0 deletions

diff --git a/arch/arm/boot/Makefile b/arch/arm/boot/Makefile
new file mode 100644
index 000000000..ba9b9a802
--- /dev/null
+++ b/arch/arm/boot/Makefile
@@ -0,0 +1,92 @@
+#
+# arch/arm/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) 1995-2002 Russell King
+#
+OBJCOPYFLAGS	:=-O binary -R .comment -S
+
+#   ZRELADDR == virt_to_phys(PAGE_OFFSET + TEXT_OFFSET)
+ifdef CONFIG_PHYS_OFFSET
+add_hex = $(shell printf 0x%x $$(( $(1) + $(2) )) )
+ZRELADDR    := $(call add_hex, $(CONFIG_PHYS_OFFSET), $(TEXT_OFFSET))
+endif
+
+PHYS_OFFSET := $(CONFIG_PHYS_OFFSET)
+export ZRELADDR PARAMS_PHYS PHYS_OFFSET
+
+targets := Image zImage xipImage bootpImage uImage
+
+ifeq ($(CONFIG_XIP_KERNEL),y)
+
+cmd_deflate_xip_data = $(CONFIG_SHELL) -c '$(src)/deflate_xip_data.sh $< $@'
+
+ifeq ($(CONFIG_XIP_DEFLATED_DATA),y)
+quiet_cmd_mkxip = XIPZ    $@
+cmd_mkxip = $(cmd_objcopy) && $(cmd_deflate_xip_data)
+else
+quiet_cmd_mkxip = $(quiet_cmd_objcopy)
+cmd_mkxip = $(cmd_objcopy)
+endif
+
+$(obj)/xipImage: vmlinux FORCE
+	$(call if_changed,mkxip)
+	@$(kecho) '  Physical Address of xipImage: $(CONFIG_XIP_PHYS_ADDR)'
+
+$(obj)/Image $(obj)/zImage: FORCE
+	@echo 'Kernel configured for XIP (CONFIG_XIP_KERNEL=y)'
+	@echo 'Only the xipImage target is available in this case'
+	@false
+
+else
+
+$(obj)/xipImage: FORCE
+	@echo 'Kernel not configured for XIP (CONFIG_XIP_KERNEL!=y)'
+	@false
+
+$(obj)/Image: vmlinux FORCE
+	$(call if_changed,objcopy)
+
+$(obj)/compressed/vmlinux: $(obj)/Image FORCE
+	$(Q)$(MAKE) $(build)=$(obj)/compressed $@
+
+$(obj)/zImage:	$(obj)/compressed/vmlinux FORCE
+	$(call if_changed,objcopy)
+
+endif
+
+ifneq ($(LOADADDR),)
+  UIMAGE_LOADADDR=$(LOADADDR)
+else
+  ifeq ($(CONFIG_ZBOOT_ROM),y)
+    UIMAGE_LOADADDR=$(CONFIG_ZBOOT_ROM_TEXT)
+  else
+    UIMAGE_LOADADDR=$(ZRELADDR)
+  endif
+endif
+
+check_for_multiple_loadaddr = \
+if [ $(words $(UIMAGE_LOADADDR)) -ne 1 ]; then \
+	echo 'multiple (or no) load addresses: $(UIMAGE_LOADADDR)'; \
+	echo 'This is incompatible with uImages'; \
+	echo 'Specify LOADADDR on the commandline to build an uImage'; \
+	false; \
+fi
+
+$(obj)/uImage:	$(obj)/zImage FORCE
+	@$(check_for_multiple_loadaddr)
+	$(call if_changed,uimage)
+
+$(obj)/bootp/bootp: $(obj)/zImage FORCE
+	$(Q)$(MAKE) $(build)=$(obj)/bootp $@
+
+$(obj)/bootpImage: $(obj)/bootp/bootp FORCE
+	$(call if_changed,objcopy)
+
+subdir-	    := bootp compressed dts