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, 152 insertions, 0 deletions

diff --git a/arch/powerpc/boot/serial.c b/arch/powerpc/boot/serial.c
new file mode 100644
index 000000000..1d221ff42
--- /dev/null
+++ b/arch/powerpc/boot/serial.c
@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Generic serial console support
+ *
+ * Author: Mark A. Greer <mgreer@mvista.com>
+ *
+ * Code in serial_edit_cmdline() copied from <file:arch/ppc/boot/simple/misc.c>
+ * and was written by Matt Porter <mporter@kernel.crashing.org>.
+ *
+ * 2001,2006 (c) MontaVista Software, Inc.
+ */
+#include <stdarg.h>
+#include <stddef.h>
+#include "types.h"
+#include "string.h"
+#include "stdio.h"
+#include "io.h"
+#include "ops.h"
+
+static int serial_open(void)
+{
+	struct serial_console_data *scdp = console_ops.data;
+	return scdp->open();
+}
+
+static void serial_write(const char *buf, int len)
+{
+	struct serial_console_data *scdp = console_ops.data;
+
+	while (*buf != '\0')
+		scdp->putc(*buf++);
+}
+
+static void serial_edit_cmdline(char *buf, int len, unsigned int timeout)
+{
+	int timer = 0, count;
+	char ch, *cp;
+	struct serial_console_data *scdp = console_ops.data;
+
+	count = strlen(buf);
+	cp = &buf[count];
+	count++;
+
+	do {
+		if (scdp->tstc()) {
+			while (((ch = scdp->getc()) != '\n') && (ch != '\r')) {
+				/* Test for backspace/delete */
+				if ((ch == '\b') || (ch == '\177')) {
+					if (cp != buf) {
+						cp--;
+						count--;
+						printf("\b \b");
+					}
+				/* Test for ^x/^u (and wipe the line) */
+				} else if ((ch == '\030') || (ch == '\025')) {
+					while (cp != buf) {
+						cp--;
+						count--;
+						printf("\b \b");
+					}
+				} else if (count < len) {
+						*cp++ = ch;
+						count++;
+						scdp->putc(ch);
+				}
+			}
+			break;  /* Exit 'timer' loop */
+		}
+		udelay(1000);  /* 1 msec */
+	} while (timer++ < timeout);
+	*cp = 0;
+}
+
+static void serial_close(void)
+{
+	struct serial_console_data *scdp = console_ops.data;
+
+	if (scdp->close)
+		scdp->close();
+}
+
+static void *serial_get_stdout_devp(void)
+{
+	void *devp;
+	char devtype[MAX_PROP_LEN];
+	char path[MAX_PATH_LEN];
+
+	devp = finddevice("/chosen");
+	if (devp == NULL)
+		goto err_out;
+
+	if (getprop(devp, "linux,stdout-path", path, MAX_PATH_LEN) > 0 ||
+		getprop(devp, "stdout-path", path, MAX_PATH_LEN) > 0) {
+		devp = finddevice(path);
+		if (devp == NULL)
+			goto err_out;
+
+		if ((getprop(devp, "device_type", devtype, sizeof(devtype)) > 0)
+				&& !strcmp(devtype, "serial"))
+			return devp;
+	}
+err_out:
+	return NULL;
+}
+
+static struct serial_console_data serial_cd;
+
+/* Node's "compatible" property determines which serial driver to use */
+int serial_console_init(void)
+{
+	void *devp;
+	int rc = -1;
+
+	devp = serial_get_stdout_devp();
+	if (devp == NULL)
+		goto err_out;
+
+	if (dt_is_compatible(devp, "ns16550") ||
+	    dt_is_compatible(devp, "pnpPNP,501"))
+		rc = ns16550_console_init(devp, &serial_cd);
+#ifdef CONFIG_CPM
+	else if (dt_is_compatible(devp, "fsl,cpm1-scc-uart") ||
+	         dt_is_compatible(devp, "fsl,cpm1-smc-uart") ||
+	         dt_is_compatible(devp, "fsl,cpm2-scc-uart") ||
+	         dt_is_compatible(devp, "fsl,cpm2-smc-uart"))
+		rc = cpm_console_init(devp, &serial_cd);
+#endif
+#ifdef CONFIG_PPC_MPC52xx
+	else if (dt_is_compatible(devp, "fsl,mpc5200-psc-uart"))
+		rc = mpc5200_psc_console_init(devp, &serial_cd);
+#endif
+#ifdef CONFIG_PPC_POWERNV
+	else if (dt_is_compatible(devp, "ibm,opal-console-raw"))
+		rc = opal_console_init(devp, &serial_cd);
+#endif
+
+	/* Add other serial console driver calls here */
+
+	if (!rc) {
+		console_ops.open = serial_open;
+		console_ops.write = serial_write;
+		console_ops.close = serial_close;
+		console_ops.data = &serial_cd;
+
+		if (serial_cd.getc)
+			console_ops.edit_cmdline = serial_edit_cmdline;
+
+		return 0;
+	}
+err_out:
+	return -1;
+}