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, 217 insertions, 0 deletions

diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
new file mode 100644
index 000000000..44f5a4397
--- /dev/null
+++ b/arch/riscv/Makefile
@@ -0,0 +1,217 @@
+# 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.
+#
+
+LDFLAGS_vmlinux := -z norelro
+ifeq ($(CONFIG_RELOCATABLE),y)
+	LDFLAGS_vmlinux += -shared -Bsymbolic -z notext
+	KBUILD_CFLAGS += -fPIE
+endif
+ifeq ($(CONFIG_DYNAMIC_FTRACE),y)
+	LDFLAGS_vmlinux += --no-relax
+	KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
+ifeq ($(CONFIG_RISCV_ISA_C),y)
+	CC_FLAGS_FTRACE := -fpatchable-function-entry=8,4
+else
+	CC_FLAGS_FTRACE := -fpatchable-function-entry=4,2
+endif
+endif
+
+ifeq ($(CONFIG_CMODEL_MEDLOW),y)
+KBUILD_CFLAGS_MODULE += -mcmodel=medany
+endif
+
+export BITS
+ifeq ($(CONFIG_ARCH_RV64I),y)
+	BITS := 64
+
+	KBUILD_CFLAGS += -mabi=lp64
+	KBUILD_AFLAGS += -mabi=lp64
+
+	KBUILD_LDFLAGS += -melf64lriscv
+
+	KBUILD_RUSTFLAGS += -Ctarget-cpu=generic-rv64 --target=riscv64imac-unknown-none-elf \
+			    -Cno-redzone
+else
+	BITS := 32
+
+	KBUILD_CFLAGS += -mabi=ilp32
+	KBUILD_AFLAGS += -mabi=ilp32
+	KBUILD_LDFLAGS += -melf32lriscv
+endif
+
+UTS_MACHINE := riscv$(BITS)
+
+# LLVM has an issue with target-features and LTO: https://github.com/llvm/llvm-project/issues/59350
+# Ensure it is aware of linker relaxation with LTO, otherwise relocations may
+# be incorrect: https://github.com/llvm/llvm-project/issues/65090
+ifeq ($(CONFIG_LTO_CLANG),y)
+	KBUILD_LDFLAGS += -mllvm -mattr=+c -mllvm -mattr=+relax
+endif
+
+ifeq ($(CONFIG_SHADOW_CALL_STACK),y)
+	KBUILD_LDFLAGS += --no-relax-gp
+endif
+
+# ISA string setting
+riscv-march-$(CONFIG_ARCH_RV32I)	:= rv32ima
+riscv-march-$(CONFIG_ARCH_RV64I)	:= rv64ima
+riscv-march-$(CONFIG_FPU)		:= $(riscv-march-y)fd
+riscv-march-$(CONFIG_RISCV_ISA_C)	:= $(riscv-march-y)c
+riscv-march-$(CONFIG_RISCV_ISA_V)	:= $(riscv-march-y)v
+
+ifneq ($(CONFIG_RISCV_ISA_C),y)
+	KBUILD_RUSTFLAGS += -Ctarget-feature=-c
+endif
+
+ifdef CONFIG_TOOLCHAIN_NEEDS_OLD_ISA_SPEC
+KBUILD_CFLAGS += -Wa,-misa-spec=2.2
+KBUILD_AFLAGS += -Wa,-misa-spec=2.2
+else
+riscv-march-$(CONFIG_TOOLCHAIN_NEEDS_EXPLICIT_ZICSR_ZIFENCEI) := $(riscv-march-y)_zicsr_zifencei
+endif
+
+KBUILD_BASE_ISA = -march=$(shell echo $(riscv-march-y) | sed -E 's/(rv32ima|rv64ima)fd([^v_]*)v?/\1\2/')
+export KBUILD_BASE_ISA
+
+# Remove F,D,V from isa string for all. Keep extensions between "fd" and "v" by
+# matching non-v and non-multi-letter extensions out with the filter ([^v_]*)
+KBUILD_CFLAGS += $(KBUILD_BASE_ISA)
+
+KBUILD_AFLAGS += -march=$(riscv-march-y)
+
+# For C code built with floating-point support, exclude V but keep F and D.
+CC_FLAGS_FPU  := -march=$(shell echo $(riscv-march-y) | sed -E 's/(rv32ima|rv64ima)([^v_]*)v?/\1\2/')
+
+KBUILD_CFLAGS += -mno-save-restore
+
+ifeq ($(CONFIG_CMODEL_MEDLOW),y)
+	KBUILD_CFLAGS += -mcmodel=medlow
+endif
+ifeq ($(CONFIG_CMODEL_MEDANY),y)
+	KBUILD_CFLAGS += -mcmodel=medany
+endif
+
+# Avoid generating .eh_frame sections.
+KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables
+
+# The RISC-V attributes frequently cause compatibility issues and provide no
+# information, so just turn them off.
+KBUILD_CFLAGS += $(call cc-option,-mno-riscv-attribute)
+KBUILD_AFLAGS += $(call cc-option,-mno-riscv-attribute)
+KBUILD_CFLAGS += $(call as-option,-Wa$(comma)-mno-arch-attr)
+KBUILD_AFLAGS += $(call as-option,-Wa$(comma)-mno-arch-attr)
+
+KBUILD_CFLAGS_MODULE += $(call cc-option,-mno-relax)
+KBUILD_AFLAGS_MODULE += $(call as-option,-Wa$(comma)-mno-relax)
+
+# GCC versions that support the "-mstrict-align" option default to allowing
+# unaligned accesses.  While unaligned accesses are explicitly allowed in the
+# RISC-V ISA, they're emulated by machine mode traps on all extant
+# architectures.  It's faster to have GCC emit only aligned accesses.
+ifneq ($(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS),y)
+KBUILD_CFLAGS += $(call cc-option,-mstrict-align)
+endif
+
+ifeq ($(CONFIG_STACKPROTECTOR_PER_TASK),y)
+prepare: stack_protector_prepare
+stack_protector_prepare: prepare0
+	$(eval KBUILD_CFLAGS += -mstack-protector-guard=tls		  \
+				-mstack-protector-guard-reg=tp		  \
+				-mstack-protector-guard-offset=$(shell	  \
+			awk '{if ($$2 == "TSK_STACK_CANARY") print $$3;}' \
+				$(objtree)/include/generated/asm-offsets.h))
+endif
+
+# arch specific predefines for sparse
+CHECKFLAGS += -D__riscv -D__riscv_xlen=$(BITS)
+
+# Default target when executing plain make
+boot					:= arch/riscv/boot
+boot-image-y				:= Image
+boot-image-$(CONFIG_KERNEL_BZIP2)	:= Image.bz2
+boot-image-$(CONFIG_KERNEL_GZIP)	:= Image.gz
+boot-image-$(CONFIG_KERNEL_LZ4)		:= Image.lz4
+boot-image-$(CONFIG_KERNEL_LZMA)	:= Image.lzma
+boot-image-$(CONFIG_KERNEL_LZO)		:= Image.lzo
+boot-image-$(CONFIG_KERNEL_ZSTD)	:= Image.zst
+boot-image-$(CONFIG_KERNEL_XZ)		:= Image.xz
+ifdef CONFIG_RISCV_M_MODE
+boot-image-$(CONFIG_SOC_CANAAN_K210)	:= loader.bin
+endif
+boot-image-$(CONFIG_EFI_ZBOOT)		:= vmlinuz.efi
+KBUILD_IMAGE				:= $(boot)/$(boot-image-y)
+
+libs-y += arch/riscv/lib/
+libs-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
+
+ifeq ($(KBUILD_EXTMOD),)
+ifeq ($(CONFIG_MMU),y)
+prepare: vdso_prepare
+vdso_prepare: prepare0
+	$(Q)$(MAKE) $(build)=arch/riscv/kernel/vdso include/generated/vdso-offsets.h
+	$(if $(CONFIG_RISCV_USER_CFI),$(Q)$(MAKE) \
+		$(build)=arch/riscv/kernel/vdso_cfi include/generated/vdso-cfi-offsets.h)
+	$(if $(CONFIG_COMPAT),$(Q)$(MAKE) \
+		$(build)=arch/riscv/kernel/compat_vdso include/generated/compat_vdso-offsets.h)
+
+endif
+endif
+
+vdso-install-$(CONFIG_MMU)		+= arch/riscv/kernel/vdso/vdso.so.dbg
+vdso-install-$(CONFIG_RISCV_USER_CFI)	+= arch/riscv/kernel/vdso_cfi/vdso-cfi.so.dbg
+vdso-install-$(CONFIG_COMPAT)	+= arch/riscv/kernel/compat_vdso/compat_vdso.so.dbg
+
+BOOT_TARGETS := Image Image.gz Image.bz2 Image.lz4 Image.lzma Image.lzo Image.zst Image.xz loader loader.bin vmlinuz.efi
+
+all:	$(notdir $(KBUILD_IMAGE))
+
+loader.bin: loader
+Image.gz Image.bz2 Image.lz4 Image.lzma Image.lzo Image.zst Image.xz loader vmlinuz.efi: Image
+
+$(BOOT_TARGETS): vmlinux
+	$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
+	@$(kecho) '  Kernel: $(boot)/$@ is ready'
+
+# the install target always installs KBUILD_IMAGE (which may be compressed)
+# but keep the zinstall target for compatibility with older releases
+install zinstall:
+	$(call cmd,install)
+
+PHONY += rv32_randconfig
+rv32_randconfig:
+	$(Q)$(MAKE) KCONFIG_ALLCONFIG=$(srctree)/arch/riscv/configs/32-bit.config \
+		-f $(srctree)/Makefile randconfig
+
+PHONY += rv64_randconfig
+rv64_randconfig:
+	$(Q)$(MAKE) KCONFIG_ALLCONFIG=$(srctree)/arch/riscv/configs/64-bit.config \
+		-f $(srctree)/Makefile randconfig
+
+PHONY += rv32_defconfig
+rv32_defconfig:
+	$(Q)$(MAKE) -f $(srctree)/Makefile defconfig 32-bit.config
+
+PHONY += rv32_nommu_virt_defconfig
+rv32_nommu_virt_defconfig:
+	$(Q)$(MAKE) -f $(srctree)/Makefile nommu_virt_defconfig 32-bit.config
+
+define archhelp
+  echo  '  Image		- Uncompressed kernel image (arch/riscv/boot/Image)'
+  echo  '  Image.gz	- Compressed kernel image (arch/riscv/boot/Image.gz)'
+  echo  '  Image.bz2	- Compressed kernel image (arch/riscv/boot/Image.bz2)'
+  echo  '  Image.lz4	- Compressed kernel image (arch/riscv/boot/Image.lz4)'
+  echo  '  Image.lzma	- Compressed kernel image (arch/riscv/boot/Image.lzma)'
+  echo  '  Image.lzo	- Compressed kernel image (arch/riscv/boot/Image.lzo)'
+  echo  '  Image.zst	- Compressed kernel image (arch/riscv/boot/Image.zst)'
+  echo  '  Image.xz	- Compressed kernel image (arch/riscv/boot/Image.xz)'
+  echo  '  vmlinuz.efi	- Compressed EFI kernel image (arch/riscv/boot/vmlinuz.efi)'
+  echo  '		  Default when CONFIG_EFI_ZBOOT=y'
+  echo  '  install	- Install kernel using (your) ~/bin/$(INSTALLKERNEL) or'
+  echo  '		  (distribution) /sbin/$(INSTALLKERNEL) or install to '
+  echo  '		  $$(INSTALL_PATH)'
+endef