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, 115 insertions, 0 deletions

diff --git a/tools/include/nolibc/Makefile b/tools/include/nolibc/Makefile
new file mode 100644
index 000000000..6d213d372
--- /dev/null
+++ b/tools/include/nolibc/Makefile
@@ -0,0 +1,115 @@
+# SPDX-License-Identifier: GPL-2.0
+# Makefile for nolibc installation and tests
+include ../../scripts/Makefile.include
+
+# we're in ".../tools/include/nolibc"
+ifeq ($(srctree),)
+srctree := $(patsubst %/tools/include/,%,$(dir $(CURDIR)))
+endif
+
+# when run as make -C tools/ nolibc_<foo> the arch is not set
+ifeq ($(ARCH),)
+include $(srctree)/scripts/subarch.include
+ARCH = $(SUBARCH)
+endif
+
+# OUTPUT is only set when run from the main makefile, otherwise
+# it defaults to this nolibc directory.
+OUTPUT ?= $(CURDIR)/
+
+architectures := alpha arm arm64 loongarch m68k mips openrisc parisc powerpc riscv s390 sh sparc x86
+arch_files := arch.h $(addsuffix .h, $(addprefix arch-, $(architectures)))
+all_files := \
+		alloca.h \
+		assert.h \
+		byteswap.h \
+		compiler.h \
+		crt.h \
+		ctype.h \
+		dirent.h \
+		elf.h \
+		endian.h \
+		err.h \
+		errno.h \
+		fcntl.h \
+		getopt.h \
+		inttypes.h \
+		limits.h \
+		math.h \
+		nolibc.h \
+		poll.h \
+		sched.h \
+		signal.h \
+		stackprotector.h \
+		std.h \
+		stdarg.h \
+		stdbool.h \
+		stddef.h \
+		stdint.h \
+		stdlib.h \
+		string.h \
+		sys.h \
+		sys/auxv.h \
+		sys/ioctl.h \
+		sys/mman.h \
+		sys/mount.h \
+		sys/prctl.h \
+		sys/ptrace.h \
+		sys/random.h \
+		sys/reboot.h \
+		sys/resource.h \
+		sys/select.h \
+		sys/stat.h \
+		sys/syscall.h \
+		sys/sysmacros.h \
+		sys/time.h \
+		sys/timerfd.h \
+		sys/types.h \
+		sys/uio.h \
+		sys/utsname.h \
+		sys/wait.h \
+		time.h \
+		types.h \
+		unistd.h \
+		stdio.h \
+
+
+# install all headers needed to support a bare-metal compiler
+all: headers
+
+install: help
+
+help:
+	@echo "Supported targets under nolibc:"
+	@echo "  all                 call \"headers\""
+	@echo "  clean               clean the sysroot"
+	@echo "  headers             prepare a multi-arch sysroot in \$${OUTPUT}sysroot"
+	@echo "  headers_standalone  like \"headers\", and also install kernel headers"
+	@echo "  help                this help"
+	@echo ""
+	@echo "These targets may also be called from tools as \"make nolibc_<target>\"."
+	@echo ""
+	@echo "Currently using the following variables:"
+	@echo "  ARCH    = $(ARCH)"
+	@echo "  OUTPUT  = $(OUTPUT)"
+	@echo ""
+
+# installs headers for all archs at once.
+headers:
+	$(Q)mkdir -p "$(OUTPUT)sysroot/include"
+	$(Q)cp --parents $(arch_files) $(all_files) "$(OUTPUT)sysroot/include/"
+
+headers_standalone: headers
+	$(Q)$(MAKE) -C $(srctree) headers_install INSTALL_HDR_PATH=$(OUTPUT)sysroot
+
+CFLAGS_s390 := -m64
+CFLAGS := $(CFLAGS_$(ARCH))
+
+headers_check: headers_standalone
+	$(Q)for header in $(filter-out crt.h std.h,$(all_files)); do \
+		$(CC) $(CFLAGS) $(CLANG_CROSS_FLAGS) -Wall -Werror -nostdinc -fsyntax-only -x c /dev/null \
+			-I$(or $(objtree),$(srctree))/usr/include -include $$header -include $$header || exit 1; \
+	done
+
+clean:
+	$(call QUIET_CLEAN, nolibc) rm -rf "$(OUTPUT)sysroot"