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>

3 files changed, 371 insertions, 0 deletions

diff --git a/tools/testing/selftests/watchdog/.gitignore b/tools/testing/selftests/watchdog/.gitignore
new file mode 100644
index 000000000..61d7b89cd
--- /dev/null
+++ b/tools/testing/selftests/watchdog/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+watchdog-test
diff --git a/tools/testing/selftests/watchdog/Makefile b/tools/testing/selftests/watchdog/Makefile
new file mode 100644
index 000000000..6b5598b55
--- /dev/null
+++ b/tools/testing/selftests/watchdog/Makefile
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0
+TEST_GEN_PROGS := watchdog-test
+
+include ../lib.mk
diff --git a/tools/testing/selftests/watchdog/watchdog-test.c b/tools/testing/selftests/watchdog/watchdog-test.c
new file mode 100644
index 000000000..4f09c5db0
--- /dev/null
+++ b/tools/testing/selftests/watchdog/watchdog-test.c
@@ -0,0 +1,365 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+* Watchdog Driver Test Program
+* - Tests all ioctls
+* - Tests Magic Close - CONFIG_WATCHDOG_NOWAYOUT
+* - Could be tested against softdog driver on systems that
+*   don't have watchdog hardware.
+* - TODO:
+* - Enhance test to add coverage for WDIOC_GETTEMP.
+*
+* Reference: Documentation/watchdog/watchdog-api.rst
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <getopt.h>
+#include <sys/ioctl.h>
+#include <linux/types.h>
+#include <linux/watchdog.h>
+
+#define DEFAULT_PING_RATE	1
+
+int fd;
+const char v = 'V';
+static const char sopts[] = "bdehp:st:Tn:NLf:i";
+static const struct option lopts[] = {
+	{"bootstatus",          no_argument, NULL, 'b'},
+	{"disable",             no_argument, NULL, 'd'},
+	{"enable",              no_argument, NULL, 'e'},
+	{"help",                no_argument, NULL, 'h'},
+	{"pingrate",      required_argument, NULL, 'p'},
+	{"status",              no_argument, NULL, 's'},
+	{"timeout",       required_argument, NULL, 't'},
+	{"gettimeout",          no_argument, NULL, 'T'},
+	{"pretimeout",    required_argument, NULL, 'n'},
+	{"getpretimeout",       no_argument, NULL, 'N'},
+	{"gettimeleft",		no_argument, NULL, 'L'},
+	{"file",          required_argument, NULL, 'f'},
+	{"info",		no_argument, NULL, 'i'},
+	{NULL,                  no_argument, NULL, 0x0}
+};
+
+/*
+ * This function simply sends an IOCTL to the driver, which in turn ticks
+ * the PC Watchdog card to reset its internal timer so it doesn't trigger
+ * a computer reset.
+ */
+static void keep_alive(void)
+{
+	int dummy;
+	int ret;
+
+	ret = ioctl(fd, WDIOC_KEEPALIVE, &dummy);
+	if (!ret)
+		printf(".");
+}
+
+/*
+ * The main program.  Run the program with "-d" to disable the card,
+ * or "-e" to enable the card.
+ */
+
+static void term(int sig)
+{
+	int ret = write(fd, &v, 1);
+
+	close(fd);
+	if (ret < 0)
+		printf("\nStopping watchdog ticks failed (%d)...\n", errno);
+	else
+		printf("\nStopping watchdog ticks...\n");
+	exit(0);
+}
+
+static void usage(char *progname)
+{
+	printf("Usage: %s [options]\n", progname);
+	printf(" -f, --file\t\tOpen watchdog device file\n");
+	printf("\t\t\tDefault is /dev/watchdog\n");
+	printf(" -i, --info\t\tShow watchdog_info\n");
+	printf(" -s, --status\t\tGet status & supported features\n");
+	printf(" -b, --bootstatus\tGet last boot status (Watchdog/POR)\n");
+	printf(" -d, --disable\t\tTurn off the watchdog timer\n");
+	printf(" -e, --enable\t\tTurn on the watchdog timer\n");
+	printf(" -h, --help\t\tPrint the help message\n");
+	printf(" -p, --pingrate=P\tSet ping rate to P seconds (default %d)\n",
+	       DEFAULT_PING_RATE);
+	printf(" -t, --timeout=T\tSet timeout to T seconds\n");
+	printf(" -T, --gettimeout\tGet the timeout\n");
+	printf(" -n, --pretimeout=T\tSet the pretimeout to T seconds\n");
+	printf(" -N, --getpretimeout\tGet the pretimeout\n");
+	printf(" -L, --gettimeleft\tGet the time left until timer expires\n");
+	printf("\n");
+	printf("Parameters are parsed left-to-right in real-time.\n");
+	printf("Example: %s -d -t 10 -p 5 -e\n", progname);
+	printf("Example: %s -t 12 -T -n 7 -N\n", progname);
+}
+
+struct wdiof_status {
+	int flag;
+	const char *status_str;
+};
+
+#define WDIOF_NUM_STATUS 8
+
+static const struct wdiof_status wdiof_status[WDIOF_NUM_STATUS] = {
+	{WDIOF_SETTIMEOUT,  "Set timeout (in seconds)"},
+	{WDIOF_MAGICCLOSE,  "Supports magic close char"},
+	{WDIOF_PRETIMEOUT,  "Pretimeout (in seconds), get/set"},
+	{WDIOF_ALARMONLY,  "Watchdog triggers a management or other external alarm not a reboot"},
+	{WDIOF_KEEPALIVEPING,  "Keep alive ping reply"},
+	{WDIOS_DISABLECARD,  "Turn off the watchdog timer"},
+	{WDIOS_ENABLECARD,  "Turn on the watchdog timer"},
+	{WDIOS_TEMPPANIC,  "Kernel panic on temperature trip"},
+};
+
+static void print_status(int flags)
+{
+	int wdiof = 0;
+
+	if (flags == WDIOS_UNKNOWN) {
+		printf("Unknown status error from WDIOC_GETSTATUS\n");
+		return;
+	}
+
+	for (wdiof = 0; wdiof < WDIOF_NUM_STATUS; wdiof++) {
+		if (flags & wdiof_status[wdiof].flag)
+			printf("Support/Status: %s\n",
+				wdiof_status[wdiof].status_str);
+	}
+}
+
+#define WDIOF_NUM_BOOTSTATUS 7
+
+static const struct wdiof_status wdiof_bootstatus[WDIOF_NUM_BOOTSTATUS] = {
+	{WDIOF_OVERHEAT, "Reset due to CPU overheat"},
+	{WDIOF_FANFAULT, "Fan failed"},
+	{WDIOF_EXTERN1, "External relay 1"},
+	{WDIOF_EXTERN2, "External relay 2"},
+	{WDIOF_POWERUNDER, "Power bad/power fault"},
+	{WDIOF_CARDRESET, "Card previously reset the CPU"},
+	{WDIOF_POWEROVER,  "Power over voltage"},
+};
+
+static void print_boot_status(int flags)
+{
+	int wdiof = 0;
+
+	if (flags == WDIOF_UNKNOWN) {
+		printf("Unknown flag error from WDIOC_GETBOOTSTATUS\n");
+		return;
+	}
+
+	if (flags == 0) {
+		printf("Last boot is caused by: Power-On-Reset\n");
+		return;
+	}
+
+	for (wdiof = 0; wdiof < WDIOF_NUM_BOOTSTATUS; wdiof++) {
+		if (flags & wdiof_bootstatus[wdiof].flag)
+			printf("Last boot is caused by: %s\n",
+				wdiof_bootstatus[wdiof].status_str);
+	}
+}
+
+int main(int argc, char *argv[])
+{
+	int flags;
+	unsigned int ping_rate = DEFAULT_PING_RATE;
+	int ret;
+	int c;
+	int oneshot = 0;
+	char *file = "/dev/watchdog";
+	struct watchdog_info info;
+	int temperature;
+
+	setbuf(stdout, NULL);
+
+	while ((c = getopt_long(argc, argv, sopts, lopts, NULL)) != -1) {
+		if (c == 'f')
+			file = optarg;
+	}
+
+	fd = open(file, O_WRONLY);
+
+	if (fd == -1) {
+		if (errno == ENOENT)
+			printf("Watchdog device (%s) not found.\n", file);
+		else if (errno == EACCES)
+			printf("Run watchdog as root.\n");
+		else
+			printf("Watchdog device open failed %s\n",
+				strerror(errno));
+		exit(-1);
+	}
+
+	/*
+	 * Validate that `file` is a watchdog device
+	 */
+	ret = ioctl(fd, WDIOC_GETSUPPORT, &info);
+	if (ret) {
+		printf("WDIOC_GETSUPPORT error '%s'\n", strerror(errno));
+		close(fd);
+		exit(ret);
+	}
+
+	optind = 0;
+
+	while ((c = getopt_long(argc, argv, sopts, lopts, NULL)) != -1) {
+		switch (c) {
+		case 'b':
+			flags = 0;
+			oneshot = 1;
+			ret = ioctl(fd, WDIOC_GETBOOTSTATUS, &flags);
+			if (!ret)
+				print_boot_status(flags);
+			else
+				printf("WDIOC_GETBOOTSTATUS error '%s'\n", strerror(errno));
+			break;
+		case 'd':
+			flags = WDIOS_DISABLECARD;
+			ret = ioctl(fd, WDIOC_SETOPTIONS, &flags);
+			if (!ret)
+				printf("Watchdog card disabled.\n");
+			else {
+				printf("WDIOS_DISABLECARD error '%s'\n", strerror(errno));
+				oneshot = 1;
+			}
+			break;
+		case 'e':
+			flags = WDIOS_ENABLECARD;
+			ret = ioctl(fd, WDIOC_SETOPTIONS, &flags);
+			if (!ret)
+				printf("Watchdog card enabled.\n");
+			else {
+				printf("WDIOS_ENABLECARD error '%s'\n", strerror(errno));
+				oneshot = 1;
+			}
+			break;
+		case 'p':
+			ping_rate = strtoul(optarg, NULL, 0);
+			if (!ping_rate)
+				ping_rate = DEFAULT_PING_RATE;
+			printf("Watchdog ping rate set to %u seconds.\n", ping_rate);
+			break;
+		case 's':
+			flags = 0;
+			oneshot = 1;
+			ret = ioctl(fd, WDIOC_GETSTATUS, &flags);
+			if (!ret)
+				print_status(flags);
+			else
+				printf("WDIOC_GETSTATUS error '%s'\n", strerror(errno));
+			ret = ioctl(fd, WDIOC_GETTEMP, &temperature);
+			if (ret)
+				printf("WDIOC_GETTEMP: '%s'\n", strerror(errno));
+			else
+				printf("Temperature %d\n", temperature);
+
+			break;
+		case 't':
+			flags = strtoul(optarg, NULL, 0);
+			ret = ioctl(fd, WDIOC_SETTIMEOUT, &flags);
+			if (!ret)
+				printf("Watchdog timeout set to %u seconds.\n", flags);
+			else {
+				printf("WDIOC_SETTIMEOUT error '%s'\n", strerror(errno));
+				oneshot = 1;
+			}
+			break;
+		case 'T':
+			oneshot = 1;
+			ret = ioctl(fd, WDIOC_GETTIMEOUT, &flags);
+			if (!ret)
+				printf("WDIOC_GETTIMEOUT returns %u seconds.\n", flags);
+			else
+				printf("WDIOC_GETTIMEOUT error '%s'\n", strerror(errno));
+			break;
+		case 'n':
+			flags = strtoul(optarg, NULL, 0);
+			ret = ioctl(fd, WDIOC_SETPRETIMEOUT, &flags);
+			if (!ret)
+				printf("Watchdog pretimeout set to %u seconds.\n", flags);
+			else {
+				printf("WDIOC_SETPRETIMEOUT error '%s'\n", strerror(errno));
+				oneshot = 1;
+			}
+			break;
+		case 'N':
+			oneshot = 1;
+			ret = ioctl(fd, WDIOC_GETPRETIMEOUT, &flags);
+			if (!ret)
+				printf("WDIOC_GETPRETIMEOUT returns %u seconds.\n", flags);
+			else
+				printf("WDIOC_GETPRETIMEOUT error '%s'\n", strerror(errno));
+			break;
+		case 'L':
+			oneshot = 1;
+			ret = ioctl(fd, WDIOC_GETTIMELEFT, &flags);
+			if (!ret)
+				printf("WDIOC_GETTIMELEFT returns %u seconds.\n", flags);
+			else
+				printf("WDIOC_GETTIMELEFT error '%s'\n", strerror(errno));
+			break;
+		case 'f':
+			/* Handled above */
+			break;
+		case 'i':
+			/*
+			 * watchdog_info was obtained as part of file open
+			 * validation. So we just show it here.
+			 */
+			oneshot = 1;
+			printf("watchdog_info:\n");
+			printf(" identity:\t\t%s\n", info.identity);
+			printf(" firmware_version:\t%u\n",
+			       info.firmware_version);
+			print_status(info.options);
+			break;
+
+		default:
+			usage(argv[0]);
+			goto end;
+		}
+	}
+
+	if (oneshot)
+		goto end;
+
+	/* Check if WDIOF_KEEPALIVEPING is supported */
+	if (!(info.options & WDIOF_KEEPALIVEPING)) {
+		printf("WDIOC_KEEPALIVE not supported by this device\n");
+		goto end;
+	}
+
+	printf("Watchdog Ticking Away!\n");
+
+	/*
+	 * Register the signals
+	 */
+	signal(SIGINT, term);
+	signal(SIGTERM, term);
+	signal(SIGKILL, term);
+	signal(SIGQUIT, term);
+
+	while (1) {
+		keep_alive();
+		sleep(ping_rate);
+	}
+end:
+	/*
+	 * Send specific magic character 'V' just in case Magic Close is
+	 * enabled to ensure watchdog gets disabled on close.
+	 */
+	ret = write(fd, &v, 1);
+	if (ret < 0)
+		printf("Stopping watchdog ticks failed (%d)...\n", errno);
+	close(fd);
+	return 0;
+}