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, 160 insertions, 0 deletions

diff --git a/drivers/mfd/vexpress-sysreg.c b/drivers/mfd/vexpress-sysreg.c
new file mode 100644
index 000000000..f49cee91f
--- /dev/null
+++ b/drivers/mfd/vexpress-sysreg.c
@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *
+ * Copyright (C) 2012 ARM Limited
+ */
+
+#include <linux/gpio/driver.h>
+#include <linux/gpio/generic.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+#include <linux/stat.h>
+
+#define SYS_ID			0x000
+#define SYS_SW			0x004
+#define SYS_LED			0x008
+#define SYS_100HZ		0x024
+#define SYS_FLAGSSET		0x030
+#define SYS_FLAGSCLR		0x034
+#define SYS_NVFLAGS		0x038
+#define SYS_NVFLAGSSET		0x038
+#define SYS_NVFLAGSCLR		0x03c
+#define SYS_MCI			0x048
+#define SYS_FLASH		0x04c
+#define SYS_CFGSW		0x058
+#define SYS_24MHZ		0x05c
+#define SYS_MISC		0x060
+#define SYS_DMA			0x064
+#define SYS_PROCID0		0x084
+#define SYS_PROCID1		0x088
+#define SYS_CFGDATA		0x0a0
+#define SYS_CFGCTRL		0x0a4
+#define SYS_CFGSTAT		0x0a8
+
+/* The sysreg block is just a random collection of various functions... */
+
+static const struct property_entry vexpress_sysreg_sys_led_props[] = {
+	PROPERTY_ENTRY_STRING("label", "sys_led"),
+	PROPERTY_ENTRY_U32("ngpios", 8),
+	{ }
+};
+
+static const struct software_node vexpress_sysreg_sys_led_swnode = {
+	.properties = vexpress_sysreg_sys_led_props,
+};
+
+static const struct property_entry vexpress_sysreg_sys_mci_props[] = {
+	PROPERTY_ENTRY_STRING("label", "sys_mci"),
+	PROPERTY_ENTRY_U32("ngpios", 2),
+	{ }
+};
+
+static const struct software_node vexpress_sysreg_sys_mci_swnode = {
+	.properties = vexpress_sysreg_sys_mci_props,
+};
+
+static const struct property_entry vexpress_sysreg_sys_flash_props[] = {
+	PROPERTY_ENTRY_STRING("label", "sys_flash"),
+	PROPERTY_ENTRY_U32("ngpios", 1),
+	{ }
+};
+
+static const struct software_node vexpress_sysreg_sys_flash_swnode = {
+	.properties = vexpress_sysreg_sys_flash_props,
+};
+
+static struct mfd_cell vexpress_sysreg_cells[] = {
+	{
+		.name = "basic-mmio-gpio",
+		.of_compatible = "arm,vexpress-sysreg,sys_led",
+		.num_resources = 1,
+		.resources = &DEFINE_RES_MEM_NAMED(SYS_LED, 0x4, "dat"),
+		.swnode = &vexpress_sysreg_sys_led_swnode,
+	}, {
+		.name = "basic-mmio-gpio",
+		.of_compatible = "arm,vexpress-sysreg,sys_mci",
+		.num_resources = 1,
+		.resources = &DEFINE_RES_MEM_NAMED(SYS_MCI, 0x4, "dat"),
+		.swnode = &vexpress_sysreg_sys_mci_swnode,
+	}, {
+		.name = "basic-mmio-gpio",
+		.of_compatible = "arm,vexpress-sysreg,sys_flash",
+		.num_resources = 1,
+		.resources = &DEFINE_RES_MEM_NAMED(SYS_FLASH, 0x4, "dat"),
+		.swnode = &vexpress_sysreg_sys_flash_swnode,
+	}, {
+		.name = "vexpress-syscfg",
+		.num_resources = 1,
+		.resources = &DEFINE_RES_MEM(SYS_MISC, 0x4c),
+	}
+};
+
+static int vexpress_sysreg_probe(struct platform_device *pdev)
+{
+	struct gpio_generic_chip *mmc_gpio_chip;
+	struct gpio_generic_chip_config config;
+	struct resource *mem;
+	void __iomem *base;
+	int ret;
+
+	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!mem)
+		return -EINVAL;
+
+	base = devm_ioremap(&pdev->dev, mem->start, resource_size(mem));
+	if (!base)
+		return -ENOMEM;
+
+	/*
+	 * Duplicated SYS_MCI pseudo-GPIO controller for compatibility with
+	 * older trees using sysreg node for MMC control lines.
+	 */
+	mmc_gpio_chip = devm_kzalloc(&pdev->dev, sizeof(*mmc_gpio_chip),
+			GFP_KERNEL);
+	if (!mmc_gpio_chip)
+		return -ENOMEM;
+
+	config = (struct gpio_generic_chip_config) {
+		.dev = &pdev->dev,
+		.sz = 4,
+		.dat = base + SYS_MCI,
+	};
+
+	ret = gpio_generic_chip_init(mmc_gpio_chip, &config);
+	if (ret)
+		return ret;
+
+	mmc_gpio_chip->gc.ngpio = 2;
+
+	ret = devm_gpiochip_add_data(&pdev->dev, &mmc_gpio_chip->gc, NULL);
+	if (ret)
+		return ret;
+
+	return devm_mfd_add_devices(&pdev->dev, PLATFORM_DEVID_AUTO,
+			vexpress_sysreg_cells,
+			ARRAY_SIZE(vexpress_sysreg_cells), mem, 0, NULL);
+}
+
+static const struct of_device_id vexpress_sysreg_match[] = {
+	{ .compatible = "arm,vexpress-sysreg", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, vexpress_sysreg_match);
+
+static struct platform_driver vexpress_sysreg_driver = {
+	.driver = {
+		.name = "vexpress-sysreg",
+		.of_match_table = vexpress_sysreg_match,
+	},
+	.probe = vexpress_sysreg_probe,
+};
+
+module_platform_driver(vexpress_sysreg_driver);
+MODULE_DESCRIPTION("Versatile Express system registers driver");
+MODULE_LICENSE("GPL v2");