From 93de2a6a4b91b72607136dd656edf03fb399d27f Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 23 Sep 2026 09:37:21 -0700 Subject: KVM: SEV: Do cache maintenance on the source VM during intra-host migration 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 Signed-off-by: Sean Christopherson Message-ID: <20260923163721.1584779-3-seanjc@google.com> Signed-off-by: Paolo Bonzini --- tools/testing/selftests/splice/.gitignore | 3 + tools/testing/selftests/splice/Makefile | 5 + tools/testing/selftests/splice/config | 1 + .../selftests/splice/default_file_splice_read.c | 9 ++ .../selftests/splice/default_file_splice_read.sh | 8 ++ tools/testing/selftests/splice/settings | 1 + .../testing/selftests/splice/short_splice_read.sh | 133 +++++++++++++++++++++ tools/testing/selftests/splice/splice_read.c | 57 +++++++++ 8 files changed, 217 insertions(+) create mode 100644 tools/testing/selftests/splice/.gitignore create mode 100644 tools/testing/selftests/splice/Makefile create mode 100644 tools/testing/selftests/splice/config create mode 100644 tools/testing/selftests/splice/default_file_splice_read.c create mode 100755 tools/testing/selftests/splice/default_file_splice_read.sh create mode 100644 tools/testing/selftests/splice/settings create mode 100755 tools/testing/selftests/splice/short_splice_read.sh create mode 100644 tools/testing/selftests/splice/splice_read.c (limited to 'tools/testing/selftests/splice') diff --git a/tools/testing/selftests/splice/.gitignore b/tools/testing/selftests/splice/.gitignore new file mode 100644 index 000000000..be8266f5d --- /dev/null +++ b/tools/testing/selftests/splice/.gitignore @@ -0,0 +1,3 @@ +# SPDX-License-Identifier: GPL-2.0-only +default_file_splice_read +splice_read diff --git a/tools/testing/selftests/splice/Makefile b/tools/testing/selftests/splice/Makefile new file mode 100644 index 000000000..541cd826d --- /dev/null +++ b/tools/testing/selftests/splice/Makefile @@ -0,0 +1,5 @@ +# SPDX-License-Identifier: GPL-2.0 +TEST_PROGS := default_file_splice_read.sh short_splice_read.sh +TEST_GEN_PROGS_EXTENDED := default_file_splice_read splice_read + +include ../lib.mk diff --git a/tools/testing/selftests/splice/config b/tools/testing/selftests/splice/config new file mode 100644 index 000000000..058c92836 --- /dev/null +++ b/tools/testing/selftests/splice/config @@ -0,0 +1 @@ +CONFIG_TEST_LKM=m diff --git a/tools/testing/selftests/splice/default_file_splice_read.c b/tools/testing/selftests/splice/default_file_splice_read.c new file mode 100644 index 000000000..a3c6e5672 --- /dev/null +++ b/tools/testing/selftests/splice/default_file_splice_read.c @@ -0,0 +1,9 @@ +// SPDX-License-Identifier: GPL-2.0 +#define _GNU_SOURCE +#include + +int main(int argc, char **argv) +{ + splice(0, 0, 1, 0, 1<<30, 0); + return 0; +} diff --git a/tools/testing/selftests/splice/default_file_splice_read.sh b/tools/testing/selftests/splice/default_file_splice_read.sh new file mode 100755 index 000000000..490db5a2e --- /dev/null +++ b/tools/testing/selftests/splice/default_file_splice_read.sh @@ -0,0 +1,8 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0 +n=`./default_file_splice_read &2 + echo "$title ..." >&2 + + set +e + "$@" + rc=$? + set -e + + case "$rc" in + 0) + echo "ok: $title succeeded" >&2 + ;; + 1) + echo "FAIL: $title should work" >&2 + ret=$(( ret + 1 )) + ;; + *) + echo "FAIL: something else went wrong" >&2 + ret=$(( ret + 1 )) + ;; + esac +} + +expect_failure() +{ + title="$1" + shift + + echo "" >&2 + echo "$title ..." >&2 + + set +e + "$@" + rc=$? + set -e + + case "$rc" in + 0) + echo "FAIL: $title unexpectedly worked" >&2 + ret=$(( ret + 1 )) + ;; + 1) + echo "ok: $title correctly failed" >&2 + ;; + *) + echo "FAIL: something else went wrong" >&2 + ret=$(( ret + 1 )) + ;; + esac +} + +do_splice() +{ + filename="$1" + bytes="$2" + expected="$3" + report="$4" + + out=$("$DIR"/splice_read "$filename" "$bytes" | cat) + if [ "$out" = "$expected" ] ; then + echo " matched $report" >&2 + return 0 + else + echo " no match: '$out' vs $report" >&2 + return 1 + fi +} + +test_splice() +{ + filename="$1" + + echo " checking $filename ..." >&2 + + full=$(cat "$filename") + rc=$? + if [ $rc -ne 0 ] ; then + return 2 + fi + + two=$(echo "$full" | grep -m1 . | cut -c-2) + + # Make sure full splice has the same contents as a standard read. + echo " splicing 4096 bytes ..." >&2 + if ! do_splice "$filename" 4096 "$full" "full read" ; then + return 1 + fi + + # Make sure a partial splice see the first two characters. + echo " splicing 2 bytes ..." >&2 + if ! do_splice "$filename" 2 "$two" "'$two'" ; then + return 1 + fi + + return 0 +} + +### /proc/$pid/ has no splice interface; these should all fail. +expect_failure "proc_single_open(), seq_read() splice" test_splice /proc/$$/limits +expect_failure "special open(), seq_read() splice" test_splice /proc/$$/comm + +### /proc/sys/ has a splice interface; these should all succeed. +expect_success "proc_handler: proc_dointvec_minmax() splice" test_splice /proc/sys/fs/nr_open +expect_success "proc_handler: proc_dostring() splice" test_splice /proc/sys/kernel/modprobe +expect_success "proc_handler: special read splice" test_splice /proc/sys/kernel/version + +### /sys/ has no splice interface; these should all fail. +if ! [ -d /sys/module/test_module/sections ] ; then + expect_success "test_module kernel module load" modprobe test_module +fi +expect_success "kernfs attr splice" test_splice /sys/module/test_module/coresize +expect_success "kernfs binattr splice" test_splice /sys/module/test_module/sections/.init.text + +exit $ret diff --git a/tools/testing/selftests/splice/splice_read.c b/tools/testing/selftests/splice/splice_read.c new file mode 100644 index 000000000..46dae6a25 --- /dev/null +++ b/tools/testing/selftests/splice/splice_read.c @@ -0,0 +1,57 @@ +// SPDX-License-Identifier: GPL-2.0 +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include + +int main(int argc, char *argv[]) +{ + int fd; + size_t size; + ssize_t spliced; + + if (argc < 2) { + fprintf(stderr, "Usage: %s INPUT [BYTES]\n", argv[0]); + return EXIT_FAILURE; + } + + fd = open(argv[1], O_RDONLY); + if (fd < 0) { + perror(argv[1]); + return EXIT_FAILURE; + } + + if (argc == 3) + size = atol(argv[2]); + else { + struct stat statbuf; + + if (fstat(fd, &statbuf) < 0) { + perror(argv[1]); + return EXIT_FAILURE; + } + + if (statbuf.st_size > INT_MAX) { + fprintf(stderr, "%s: Too big\n", argv[1]); + return EXIT_FAILURE; + } + + size = statbuf.st_size; + } + + /* splice(2) file to stdout. */ + spliced = splice(fd, NULL, STDOUT_FILENO, NULL, + size, SPLICE_F_MOVE); + if (spliced < 0) { + perror("splice"); + return EXIT_FAILURE; + } + + close(fd); + return EXIT_SUCCESS; +} -- cgit v1.3.1