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, 243 insertions, 0 deletions

diff --git a/drivers/nvmem/meson-mx-efuse.c b/drivers/nvmem/meson-mx-efuse.c
new file mode 100644
index 000000000..8a16f5f02
--- /dev/null
+++ b/drivers/nvmem/meson-mx-efuse.c
@@ -0,0 +1,243 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Amlogic Meson6, Meson8 and Meson8b eFuse Driver
+ *
+ * Copyright (c) 2017 Martin Blumenstingl <martin.blumenstingl@googlemail.com>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/sizes.h>
+#include <linux/slab.h>
+
+#define MESON_MX_EFUSE_CNTL1					0x04
+#define MESON_MX_EFUSE_CNTL1_PD_ENABLE				BIT(27)
+#define MESON_MX_EFUSE_CNTL1_AUTO_RD_BUSY			BIT(26)
+#define MESON_MX_EFUSE_CNTL1_AUTO_RD_START			BIT(25)
+#define MESON_MX_EFUSE_CNTL1_AUTO_RD_ENABLE			BIT(24)
+#define MESON_MX_EFUSE_CNTL1_BYTE_WR_DATA			GENMASK(23, 16)
+#define MESON_MX_EFUSE_CNTL1_AUTO_WR_BUSY			BIT(14)
+#define MESON_MX_EFUSE_CNTL1_AUTO_WR_START			BIT(13)
+#define MESON_MX_EFUSE_CNTL1_AUTO_WR_ENABLE			BIT(12)
+#define MESON_MX_EFUSE_CNTL1_BYTE_ADDR_SET			BIT(11)
+#define MESON_MX_EFUSE_CNTL1_BYTE_ADDR_MASK			GENMASK(10, 0)
+
+#define MESON_MX_EFUSE_CNTL2					0x08
+
+#define MESON_MX_EFUSE_CNTL4					0x10
+#define MESON_MX_EFUSE_CNTL4_ENCRYPT_ENABLE			BIT(10)
+
+struct meson_mx_efuse_platform_data {
+	const char *name;
+	unsigned int word_size;
+};
+
+struct meson_mx_efuse {
+	void __iomem *base;
+	struct clk *core_clk;
+	struct nvmem_config config;
+};
+
+static void meson_mx_efuse_mask_bits(struct meson_mx_efuse *efuse, u32 reg,
+				     u32 mask, u32 set)
+{
+	u32 data;
+
+	data = readl(efuse->base + reg);
+	data &= ~mask;
+	data |= (set & mask);
+
+	writel(data, efuse->base + reg);
+}
+
+static int meson_mx_efuse_hw_enable(struct meson_mx_efuse *efuse)
+{
+	int err;
+
+	err = clk_prepare_enable(efuse->core_clk);
+	if (err)
+		return err;
+
+	/* power up the efuse */
+	meson_mx_efuse_mask_bits(efuse, MESON_MX_EFUSE_CNTL1,
+				 MESON_MX_EFUSE_CNTL1_PD_ENABLE, 0);
+
+	meson_mx_efuse_mask_bits(efuse, MESON_MX_EFUSE_CNTL4,
+				 MESON_MX_EFUSE_CNTL4_ENCRYPT_ENABLE, 0);
+
+	return 0;
+}
+
+static void meson_mx_efuse_hw_disable(struct meson_mx_efuse *efuse)
+{
+	meson_mx_efuse_mask_bits(efuse, MESON_MX_EFUSE_CNTL1,
+				 MESON_MX_EFUSE_CNTL1_PD_ENABLE,
+				 MESON_MX_EFUSE_CNTL1_PD_ENABLE);
+
+	clk_disable_unprepare(efuse->core_clk);
+}
+
+static int meson_mx_efuse_read_addr(struct meson_mx_efuse *efuse,
+				    unsigned int addr, u32 *value)
+{
+	int err;
+	u32 regval;
+
+	/* write the address to read */
+	regval = FIELD_PREP(MESON_MX_EFUSE_CNTL1_BYTE_ADDR_MASK, addr);
+	meson_mx_efuse_mask_bits(efuse, MESON_MX_EFUSE_CNTL1,
+				 MESON_MX_EFUSE_CNTL1_BYTE_ADDR_MASK, regval);
+
+	/* inform the hardware that we changed the address */
+	meson_mx_efuse_mask_bits(efuse, MESON_MX_EFUSE_CNTL1,
+				 MESON_MX_EFUSE_CNTL1_BYTE_ADDR_SET,
+				 MESON_MX_EFUSE_CNTL1_BYTE_ADDR_SET);
+	meson_mx_efuse_mask_bits(efuse, MESON_MX_EFUSE_CNTL1,
+				 MESON_MX_EFUSE_CNTL1_BYTE_ADDR_SET, 0);
+
+	/* start the read process */
+	meson_mx_efuse_mask_bits(efuse, MESON_MX_EFUSE_CNTL1,
+				 MESON_MX_EFUSE_CNTL1_AUTO_RD_START,
+				 MESON_MX_EFUSE_CNTL1_AUTO_RD_START);
+	meson_mx_efuse_mask_bits(efuse, MESON_MX_EFUSE_CNTL1,
+				 MESON_MX_EFUSE_CNTL1_AUTO_RD_START, 0);
+
+	/*
+	 * perform a dummy read to ensure that the HW has the RD_BUSY bit set
+	 * when polling for the status below.
+	 */
+	readl(efuse->base + MESON_MX_EFUSE_CNTL1);
+
+	err = readl_poll_timeout_atomic(efuse->base + MESON_MX_EFUSE_CNTL1,
+			regval,
+			(!(regval & MESON_MX_EFUSE_CNTL1_AUTO_RD_BUSY)),
+			1, 1000);
+	if (err) {
+		dev_err(efuse->config.dev,
+			"Timeout while reading efuse address %u\n", addr);
+		return err;
+	}
+
+	*value = readl(efuse->base + MESON_MX_EFUSE_CNTL2);
+
+	return 0;
+}
+
+static int meson_mx_efuse_read(void *context, unsigned int offset,
+			       void *buf, size_t bytes)
+{
+	struct meson_mx_efuse *efuse = context;
+	u32 tmp;
+	int err, i, addr;
+
+	err = meson_mx_efuse_hw_enable(efuse);
+	if (err)
+		return err;
+
+	meson_mx_efuse_mask_bits(efuse, MESON_MX_EFUSE_CNTL1,
+				 MESON_MX_EFUSE_CNTL1_AUTO_RD_ENABLE,
+				 MESON_MX_EFUSE_CNTL1_AUTO_RD_ENABLE);
+
+	for (i = 0; i < bytes; i += efuse->config.word_size) {
+		addr = (offset + i) / efuse->config.word_size;
+
+		err = meson_mx_efuse_read_addr(efuse, addr, &tmp);
+		if (err)
+			break;
+
+		memcpy(buf + i, &tmp,
+		       min_t(size_t, bytes - i, efuse->config.word_size));
+	}
+
+	meson_mx_efuse_mask_bits(efuse, MESON_MX_EFUSE_CNTL1,
+				 MESON_MX_EFUSE_CNTL1_AUTO_RD_ENABLE, 0);
+
+	meson_mx_efuse_hw_disable(efuse);
+
+	return err;
+}
+
+static const struct meson_mx_efuse_platform_data meson6_efuse_data = {
+	.name = "meson6-efuse",
+	.word_size = 1,
+};
+
+static const struct meson_mx_efuse_platform_data meson8_efuse_data = {
+	.name = "meson8-efuse",
+	.word_size = 4,
+};
+
+static const struct meson_mx_efuse_platform_data meson8b_efuse_data = {
+	.name = "meson8b-efuse",
+	.word_size = 4,
+};
+
+static const struct of_device_id meson_mx_efuse_match[] = {
+	{ .compatible = "amlogic,meson6-efuse", .data = &meson6_efuse_data },
+	{ .compatible = "amlogic,meson8-efuse", .data = &meson8_efuse_data },
+	{ .compatible = "amlogic,meson8b-efuse", .data = &meson8b_efuse_data },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, meson_mx_efuse_match);
+
+static int meson_mx_efuse_probe(struct platform_device *pdev)
+{
+	const struct meson_mx_efuse_platform_data *drvdata;
+	struct meson_mx_efuse *efuse;
+	struct nvmem_device *nvmem;
+
+	drvdata = of_device_get_match_data(&pdev->dev);
+	if (!drvdata)
+		return -EINVAL;
+
+	efuse = devm_kzalloc(&pdev->dev, sizeof(*efuse), GFP_KERNEL);
+	if (!efuse)
+		return -ENOMEM;
+
+	efuse->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(efuse->base))
+		return PTR_ERR(efuse->base);
+
+	efuse->config.name = drvdata->name;
+	efuse->config.owner = THIS_MODULE;
+	efuse->config.dev = &pdev->dev;
+	efuse->config.priv = efuse;
+	efuse->config.add_legacy_fixed_of_cells = true;
+	efuse->config.stride = drvdata->word_size;
+	efuse->config.word_size = drvdata->word_size;
+	efuse->config.size = SZ_512;
+	efuse->config.read_only = true;
+	efuse->config.reg_read = meson_mx_efuse_read;
+
+	efuse->core_clk = devm_clk_get(&pdev->dev, "core");
+	if (IS_ERR(efuse->core_clk)) {
+		dev_err(&pdev->dev, "Failed to get core clock\n");
+		return PTR_ERR(efuse->core_clk);
+	}
+
+	nvmem = devm_nvmem_register(&pdev->dev, &efuse->config);
+
+	return PTR_ERR_OR_ZERO(nvmem);
+}
+
+static struct platform_driver meson_mx_efuse_driver = {
+	.probe = meson_mx_efuse_probe,
+	.driver = {
+		.name = "meson-mx-efuse",
+		.of_match_table = meson_mx_efuse_match,
+	},
+};
+
+module_platform_driver(meson_mx_efuse_driver);
+
+MODULE_AUTHOR("Martin Blumenstingl <martin.blumenstingl@googlemail.com>");
+MODULE_DESCRIPTION("Amlogic Meson MX eFuse NVMEM driver");
+MODULE_LICENSE("GPL v2");