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, 147 insertions, 0 deletions

diff --git a/drivers/gpio/gpio-amdpt.c b/drivers/gpio/gpio-amdpt.c
new file mode 100644
index 000000000..8458a6949
--- /dev/null
+++ b/drivers/gpio/gpio-amdpt.c
@@ -0,0 +1,147 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AMD Promontory GPIO driver
+ *
+ * Copyright (C) 2015 ASMedia Technology Inc.
+ * Author: YD Tseng <yd_tseng@asmedia.com.tw>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/gpio/driver.h>
+#include <linux/gpio/generic.h>
+#include <linux/spinlock.h>
+#include <linux/acpi.h>
+#include <linux/platform_device.h>
+
+#define PT_TOTAL_GPIO 8
+#define PT_TOTAL_GPIO_EX 24
+
+/* PCI-E MMIO register offsets */
+#define PT_DIRECTION_REG   0x00
+#define PT_INPUTDATA_REG   0x04
+#define PT_OUTPUTDATA_REG  0x08
+#define PT_CLOCKRATE_REG   0x0C
+#define PT_SYNC_REG        0x28
+
+struct pt_gpio_chip {
+	struct gpio_generic_chip chip;
+	void __iomem             *reg_base;
+};
+
+static int pt_gpio_request(struct gpio_chip *gc, unsigned offset)
+{
+	struct gpio_generic_chip *gen_gc = to_gpio_generic_chip(gc);
+	struct pt_gpio_chip *pt_gpio = gpiochip_get_data(gc);
+	u32 using_pins;
+
+	dev_dbg(gc->parent, "pt_gpio_request offset=%x\n", offset);
+
+	guard(gpio_generic_lock_irqsave)(gen_gc);
+
+	using_pins = readl(pt_gpio->reg_base + PT_SYNC_REG);
+	if (using_pins & BIT(offset)) {
+		dev_warn(gc->parent, "PT GPIO pin %x reconfigured\n",
+			 offset);
+		return -EINVAL;
+	}
+
+	writel(using_pins | BIT(offset), pt_gpio->reg_base + PT_SYNC_REG);
+
+	return 0;
+}
+
+static void pt_gpio_free(struct gpio_chip *gc, unsigned offset)
+{
+	struct gpio_generic_chip *gen_gc = to_gpio_generic_chip(gc);
+	struct pt_gpio_chip *pt_gpio = gpiochip_get_data(gc);
+	u32 using_pins;
+
+	guard(gpio_generic_lock_irqsave)(gen_gc);
+
+	using_pins = readl(pt_gpio->reg_base + PT_SYNC_REG);
+	using_pins &= ~BIT(offset);
+	writel(using_pins, pt_gpio->reg_base + PT_SYNC_REG);
+
+	dev_dbg(gc->parent, "pt_gpio_free offset=%x\n", offset);
+}
+
+static int pt_gpio_probe(struct platform_device *pdev)
+{
+	struct gpio_generic_chip_config config;
+	struct device *dev = &pdev->dev;
+	struct pt_gpio_chip *pt_gpio;
+	int ret = 0;
+
+	if (!ACPI_COMPANION(dev)) {
+		dev_err(dev, "PT GPIO device node not found\n");
+		return -ENODEV;
+	}
+
+	pt_gpio = devm_kzalloc(dev, sizeof(struct pt_gpio_chip), GFP_KERNEL);
+	if (!pt_gpio)
+		return -ENOMEM;
+
+	pt_gpio->reg_base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(pt_gpio->reg_base)) {
+		dev_err(dev, "Failed to map MMIO resource for PT GPIO.\n");
+		return PTR_ERR(pt_gpio->reg_base);
+	}
+
+	config = (struct gpio_generic_chip_config) {
+		.dev = dev,
+		.sz = 4,
+		.dat = pt_gpio->reg_base + PT_INPUTDATA_REG,
+		.set = pt_gpio->reg_base + PT_OUTPUTDATA_REG,
+		.dirout = pt_gpio->reg_base + PT_DIRECTION_REG,
+		.flags = GPIO_GENERIC_READ_OUTPUT_REG_SET,
+	};
+
+	ret = gpio_generic_chip_init(&pt_gpio->chip, &config);
+	if (ret) {
+		dev_err(dev, "failed to initialize the generic GPIO chip\n");
+		return ret;
+	}
+
+	pt_gpio->chip.gc.owner = THIS_MODULE;
+	pt_gpio->chip.gc.request = pt_gpio_request;
+	pt_gpio->chip.gc.free = pt_gpio_free;
+	pt_gpio->chip.gc.ngpio = (uintptr_t)device_get_match_data(dev);
+
+	ret = devm_gpiochip_add_data(dev, &pt_gpio->chip.gc, pt_gpio);
+	if (ret) {
+		dev_err(dev, "Failed to register GPIO lib\n");
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, pt_gpio);
+
+	/* initialize register setting */
+	writel(0, pt_gpio->reg_base + PT_SYNC_REG);
+	writel(0, pt_gpio->reg_base + PT_CLOCKRATE_REG);
+
+	dev_dbg(dev, "PT GPIO driver loaded\n");
+	return ret;
+}
+
+static const struct acpi_device_id pt_gpio_acpi_match[] = {
+	{ "AMDF030", PT_TOTAL_GPIO },
+	{ "AMDIF030", PT_TOTAL_GPIO },
+	{ "AMDIF031", PT_TOTAL_GPIO_EX },
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, pt_gpio_acpi_match);
+
+static struct platform_driver pt_gpio_driver = {
+	.driver = {
+		.name = "pt-gpio",
+		.acpi_match_table = ACPI_PTR(pt_gpio_acpi_match),
+	},
+	.probe = pt_gpio_probe,
+};
+
+module_platform_driver(pt_gpio_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("YD Tseng <yd_tseng@asmedia.com.tw>");
+MODULE_DESCRIPTION("AMD Promontory GPIO Driver");