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, 131 insertions, 0 deletions

diff --git a/arch/mips/bcm63xx/dev-flash.c b/arch/mips/bcm63xx/dev-flash.c
new file mode 100644
index 000000000..f9cc015d3
--- /dev/null
+++ b/arch/mips/bcm63xx/dev-flash.c
@@ -0,0 +1,131 @@
+/*
+ * Broadcom BCM63xx flash registration
+ *
+ * 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.
+ *
+ * Copyright (C) 2008 Maxime Bizon <mbizon@freebox.fr>
+ * Copyright (C) 2008 Florian Fainelli <florian@openwrt.org>
+ * Copyright (C) 2012 Jonas Gorski <jonas.gorski@gmail.com>
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/partitions.h>
+#include <linux/mtd/physmap.h>
+
+#include <bcm63xx_cpu.h>
+#include <bcm63xx_dev_flash.h>
+#include <bcm63xx_regs.h>
+#include <bcm63xx_io.h>
+
+static struct mtd_partition mtd_partitions[] = {
+	{
+		.name		= "cfe",
+		.offset		= 0x0,
+		.size		= 0x40000,
+	}
+};
+
+static const char *bcm63xx_part_types[] = { "bcm63xxpart", NULL };
+
+static struct physmap_flash_data flash_data = {
+	.width			= 2,
+	.parts			= mtd_partitions,
+	.part_probe_types	= bcm63xx_part_types,
+};
+
+static struct resource mtd_resources[] = {
+	{
+		.start		= 0,	/* filled at runtime */
+		.end		= 0,	/* filled at runtime */
+		.flags		= IORESOURCE_MEM,
+	}
+};
+
+static struct platform_device mtd_dev = {
+	.name			= "physmap-flash",
+	.resource		= mtd_resources,
+	.num_resources		= ARRAY_SIZE(mtd_resources),
+	.dev			= {
+		.platform_data	= &flash_data,
+	},
+};
+
+static int __init bcm63xx_detect_flash_type(void)
+{
+	u32 val;
+
+	switch (bcm63xx_get_cpu_id()) {
+	case BCM6328_CPU_ID:
+		val = bcm_misc_readl(MISC_STRAPBUS_6328_REG);
+		if (val & STRAPBUS_6328_BOOT_SEL_SERIAL)
+			return BCM63XX_FLASH_TYPE_SERIAL;
+		else
+			return BCM63XX_FLASH_TYPE_NAND;
+	case BCM6338_CPU_ID:
+	case BCM6345_CPU_ID:
+	case BCM6348_CPU_ID:
+		/* no way to auto detect so assume parallel */
+		return BCM63XX_FLASH_TYPE_PARALLEL;
+	case BCM3368_CPU_ID:
+	case BCM6358_CPU_ID:
+		val = bcm_gpio_readl(GPIO_STRAPBUS_REG);
+		if (val & STRAPBUS_6358_BOOT_SEL_PARALLEL)
+			return BCM63XX_FLASH_TYPE_PARALLEL;
+		else
+			return BCM63XX_FLASH_TYPE_SERIAL;
+	case BCM6362_CPU_ID:
+		val = bcm_misc_readl(MISC_STRAPBUS_6362_REG);
+		if (val & STRAPBUS_6362_BOOT_SEL_SERIAL)
+			return BCM63XX_FLASH_TYPE_SERIAL;
+		else
+			return BCM63XX_FLASH_TYPE_NAND;
+	case BCM6368_CPU_ID:
+		val = bcm_gpio_readl(GPIO_STRAPBUS_REG);
+		switch (val & STRAPBUS_6368_BOOT_SEL_MASK) {
+		case STRAPBUS_6368_BOOT_SEL_NAND:
+			return BCM63XX_FLASH_TYPE_NAND;
+		case STRAPBUS_6368_BOOT_SEL_SERIAL:
+			return BCM63XX_FLASH_TYPE_SERIAL;
+		case STRAPBUS_6368_BOOT_SEL_PARALLEL:
+			return BCM63XX_FLASH_TYPE_PARALLEL;
+		}
+		fallthrough;
+	default:
+		return -EINVAL;
+	}
+}
+
+int __init bcm63xx_flash_register(void)
+{
+	int flash_type;
+	u32 val;
+
+	flash_type = bcm63xx_detect_flash_type();
+
+	switch (flash_type) {
+	case BCM63XX_FLASH_TYPE_PARALLEL:
+		/* read base address of boot chip select (0) */
+		val = bcm_mpi_readl(MPI_CSBASE_REG(0));
+		val &= MPI_CSBASE_BASE_MASK;
+
+		mtd_resources[0].start = val;
+		mtd_resources[0].end = 0x1FFFFFFF;
+
+		return platform_device_register(&mtd_dev);
+	case BCM63XX_FLASH_TYPE_SERIAL:
+		pr_warn("unsupported serial flash detected\n");
+		return -ENODEV;
+	case BCM63XX_FLASH_TYPE_NAND:
+		pr_warn("unsupported NAND flash detected\n");
+		return -ENODEV;
+	default:
+		pr_err("flash detection failed for BCM%x: %d\n",
+		       bcm63xx_get_cpu_id(), flash_type);
+		return -ENODEV;
+	}
+}