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, 157 insertions, 0 deletions

diff --git a/drivers/gpio/gpio-mlxbf.c b/drivers/gpio/gpio-mlxbf.c
new file mode 100644
index 000000000..a18fedbc4
--- /dev/null
+++ b/drivers/gpio/gpio-mlxbf.c
@@ -0,0 +1,157 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/acpi.h>
+#include <linux/bitops.h>
+#include <linux/device.h>
+#include <linux/gpio/driver.h>
+#include <linux/gpio/generic.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm.h>
+#include <linux/resource.h>
+#include <linux/types.h>
+
+/* Number of pins on BlueField */
+#define MLXBF_GPIO_NR 54
+
+/* Pad Electrical Controls. */
+#define MLXBF_GPIO_PAD_CONTROL_FIRST_WORD 0x0700
+#define MLXBF_GPIO_PAD_CONTROL_1_FIRST_WORD 0x0708
+#define MLXBF_GPIO_PAD_CONTROL_2_FIRST_WORD 0x0710
+#define MLXBF_GPIO_PAD_CONTROL_3_FIRST_WORD 0x0718
+
+#define MLXBF_GPIO_PIN_DIR_I 0x1040
+#define MLXBF_GPIO_PIN_DIR_O 0x1048
+#define MLXBF_GPIO_PIN_STATE 0x1000
+#define MLXBF_GPIO_SCRATCHPAD 0x20
+
+#ifdef CONFIG_PM
+struct mlxbf_gpio_context_save_regs {
+	u64 scratchpad;
+	u64 pad_control[MLXBF_GPIO_NR];
+	u64 pin_dir_i;
+	u64 pin_dir_o;
+};
+#endif
+
+/* Device state structure. */
+struct mlxbf_gpio_state {
+	struct gpio_generic_chip chip;
+
+	/* Memory Address */
+	void __iomem *base;
+
+#ifdef CONFIG_PM
+	struct mlxbf_gpio_context_save_regs csave_regs;
+#endif
+};
+
+static int mlxbf_gpio_probe(struct platform_device *pdev)
+{
+	struct gpio_generic_chip_config config;
+	struct mlxbf_gpio_state *gs;
+	struct device *dev = &pdev->dev;
+	struct gpio_chip *gc;
+	int ret;
+
+	gs = devm_kzalloc(&pdev->dev, sizeof(*gs), GFP_KERNEL);
+	if (!gs)
+		return -ENOMEM;
+
+	gs->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(gs->base))
+		return PTR_ERR(gs->base);
+
+	gc = &gs->chip.gc;
+
+	config = (struct gpio_generic_chip_config) {
+		.dev = dev,
+		.sz = 8,
+		.dat = gs->base + MLXBF_GPIO_PIN_STATE,
+		.dirout = gs->base + MLXBF_GPIO_PIN_DIR_O,
+		.dirin =  gs->base + MLXBF_GPIO_PIN_DIR_I,
+	};
+
+	ret = gpio_generic_chip_init(&gs->chip, &config);
+	if (ret)
+		return -ENODEV;
+
+	gc->owner = THIS_MODULE;
+	gc->ngpio = MLXBF_GPIO_NR;
+
+	ret = devm_gpiochip_add_data(dev, &gs->chip.gc, gs);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed adding memory mapped gpiochip\n");
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, gs);
+	dev_info(&pdev->dev, "registered Mellanox BlueField GPIO");
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int mlxbf_gpio_suspend(struct platform_device *pdev, pm_message_t state)
+{
+	struct mlxbf_gpio_state *gs = platform_get_drvdata(pdev);
+
+	gs->csave_regs.scratchpad = readq(gs->base + MLXBF_GPIO_SCRATCHPAD);
+	gs->csave_regs.pad_control[0] =
+		readq(gs->base + MLXBF_GPIO_PAD_CONTROL_FIRST_WORD);
+	gs->csave_regs.pad_control[1] =
+		readq(gs->base + MLXBF_GPIO_PAD_CONTROL_1_FIRST_WORD);
+	gs->csave_regs.pad_control[2] =
+		readq(gs->base + MLXBF_GPIO_PAD_CONTROL_2_FIRST_WORD);
+	gs->csave_regs.pad_control[3] =
+		readq(gs->base + MLXBF_GPIO_PAD_CONTROL_3_FIRST_WORD);
+	gs->csave_regs.pin_dir_i = readq(gs->base + MLXBF_GPIO_PIN_DIR_I);
+	gs->csave_regs.pin_dir_o = readq(gs->base + MLXBF_GPIO_PIN_DIR_O);
+
+	return 0;
+}
+
+static int mlxbf_gpio_resume(struct platform_device *pdev)
+{
+	struct mlxbf_gpio_state *gs = platform_get_drvdata(pdev);
+
+	writeq(gs->csave_regs.scratchpad, gs->base + MLXBF_GPIO_SCRATCHPAD);
+	writeq(gs->csave_regs.pad_control[0],
+	       gs->base + MLXBF_GPIO_PAD_CONTROL_FIRST_WORD);
+	writeq(gs->csave_regs.pad_control[1],
+	       gs->base + MLXBF_GPIO_PAD_CONTROL_1_FIRST_WORD);
+	writeq(gs->csave_regs.pad_control[2],
+	       gs->base + MLXBF_GPIO_PAD_CONTROL_2_FIRST_WORD);
+	writeq(gs->csave_regs.pad_control[3],
+	       gs->base + MLXBF_GPIO_PAD_CONTROL_3_FIRST_WORD);
+	writeq(gs->csave_regs.pin_dir_i, gs->base + MLXBF_GPIO_PIN_DIR_I);
+	writeq(gs->csave_regs.pin_dir_o, gs->base + MLXBF_GPIO_PIN_DIR_O);
+
+	return 0;
+}
+#endif
+
+static const struct acpi_device_id __maybe_unused mlxbf_gpio_acpi_match[] = {
+	{ "MLNXBF02", 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(acpi, mlxbf_gpio_acpi_match);
+
+static struct platform_driver mlxbf_gpio_driver = {
+	.driver = {
+		.name = "mlxbf_gpio",
+		.acpi_match_table = ACPI_PTR(mlxbf_gpio_acpi_match),
+	},
+	.probe    = mlxbf_gpio_probe,
+#ifdef CONFIG_PM
+	.suspend  = mlxbf_gpio_suspend,
+	.resume   = mlxbf_gpio_resume,
+#endif
+};
+
+module_platform_driver(mlxbf_gpio_driver);
+
+MODULE_DESCRIPTION("Mellanox BlueField GPIO Driver");
+MODULE_AUTHOR("Mellanox Technologies");
+MODULE_LICENSE("GPL");