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, 232 insertions, 0 deletions

diff --git a/drivers/nvmem/sunxi_sid.c b/drivers/nvmem/sunxi_sid.c
new file mode 100644
index 000000000..ba14a7620
--- /dev/null
+++ b/drivers/nvmem/sunxi_sid.c
@@ -0,0 +1,232 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Allwinner sunXi SoCs Security ID support.
+ *
+ * Copyright (c) 2013 Oliver Schinagl <oliver@schinagl.nl>
+ * Copyright (C) 2014 Maxime Ripard <maxime.ripard@free-electrons.com>
+ */
+
+#include <linux/device.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/slab.h>
+#include <linux/random.h>
+
+/* Registers and special values for doing register-based SID readout on H3 */
+#define SUN8I_SID_PRCTL		0x40
+#define SUN8I_SID_RDKEY		0x60
+
+#define SUN8I_SID_OFFSET_MASK	0x1FF
+#define SUN8I_SID_OFFSET_SHIFT	16
+#define SUN8I_SID_OP_LOCK	(0xAC << 8)
+#define SUN8I_SID_READ		BIT(1)
+
+struct sunxi_sid_cfg {
+	u32	value_offset;
+	u32	size;
+	bool	need_register_readout;
+};
+
+struct sunxi_sid {
+	void __iomem		*base;
+	u32			value_offset;
+};
+
+static int sunxi_sid_read(void *context, unsigned int offset,
+			  void *val, size_t bytes)
+{
+	struct sunxi_sid *sid = context;
+	u32 word;
+
+	/* .stride = 4 so offset is guaranteed to be aligned */
+	__ioread32_copy(val, sid->base + sid->value_offset + offset, bytes / 4);
+
+	val += round_down(bytes, 4);
+	offset += round_down(bytes, 4);
+	bytes = bytes % 4;
+
+	if (!bytes)
+		return 0;
+
+	/* Handle any trailing bytes */
+	word = readl_relaxed(sid->base + sid->value_offset + offset);
+	memcpy(val, &word, bytes);
+
+	return 0;
+}
+
+static int sun8i_sid_register_readout(const struct sunxi_sid *sid,
+				      const unsigned int offset,
+				      u32 *out)
+{
+	u32 reg_val;
+	int ret;
+
+	/* Set word, lock access, and set read command */
+	reg_val = (offset & SUN8I_SID_OFFSET_MASK)
+		  << SUN8I_SID_OFFSET_SHIFT;
+	reg_val |= SUN8I_SID_OP_LOCK | SUN8I_SID_READ;
+	writel(reg_val, sid->base + SUN8I_SID_PRCTL);
+
+	ret = readl_poll_timeout(sid->base + SUN8I_SID_PRCTL, reg_val,
+				 !(reg_val & SUN8I_SID_READ), 100, 250000);
+	if (ret)
+		return ret;
+
+	if (out)
+		*out = readl(sid->base + SUN8I_SID_RDKEY);
+
+	writel(0, sid->base + SUN8I_SID_PRCTL);
+
+	return 0;
+}
+
+/*
+ * On Allwinner H3, the value on the 0x200 offset of the SID controller seems
+ * to be not reliable at all.
+ * Read by the registers instead.
+ */
+static int sun8i_sid_read_by_reg(void *context, unsigned int offset,
+				 void *val, size_t bytes)
+{
+	struct sunxi_sid *sid = context;
+	u32 word;
+	int ret;
+
+	/* .stride = 4 so offset is guaranteed to be aligned */
+	while (bytes >= 4) {
+		ret = sun8i_sid_register_readout(sid, offset, val);
+		if (ret)
+			return ret;
+
+		val += 4;
+		offset += 4;
+		bytes -= 4;
+	}
+
+	if (!bytes)
+		return 0;
+
+	/* Handle any trailing bytes */
+	ret = sun8i_sid_register_readout(sid, offset, &word);
+	if (ret)
+		return ret;
+
+	memcpy(val, &word, bytes);
+
+	return 0;
+}
+
+static int sunxi_sid_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct nvmem_config *nvmem_cfg;
+	struct nvmem_device *nvmem;
+	struct sunxi_sid *sid;
+	int size;
+	char *randomness;
+	const struct sunxi_sid_cfg *cfg;
+
+	sid = devm_kzalloc(dev, sizeof(*sid), GFP_KERNEL);
+	if (!sid)
+		return -ENOMEM;
+
+	cfg = of_device_get_match_data(dev);
+	if (!cfg)
+		return -EINVAL;
+	sid->value_offset = cfg->value_offset;
+
+	sid->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(sid->base))
+		return PTR_ERR(sid->base);
+
+	size = cfg->size;
+
+	nvmem_cfg = devm_kzalloc(dev, sizeof(*nvmem_cfg), GFP_KERNEL);
+	if (!nvmem_cfg)
+		return -ENOMEM;
+
+	nvmem_cfg->dev = dev;
+	nvmem_cfg->name = "sunxi-sid";
+	nvmem_cfg->type = NVMEM_TYPE_OTP;
+	nvmem_cfg->add_legacy_fixed_of_cells = true;
+	nvmem_cfg->read_only = true;
+	nvmem_cfg->size = cfg->size;
+	nvmem_cfg->word_size = 1;
+	nvmem_cfg->stride = 4;
+	nvmem_cfg->priv = sid;
+	if (cfg->need_register_readout)
+		nvmem_cfg->reg_read = sun8i_sid_read_by_reg;
+	else
+		nvmem_cfg->reg_read = sunxi_sid_read;
+
+	nvmem = devm_nvmem_register(dev, nvmem_cfg);
+	if (IS_ERR(nvmem))
+		return PTR_ERR(nvmem);
+
+	randomness = kzalloc(size, GFP_KERNEL);
+	if (!randomness)
+		return -ENOMEM;
+
+	nvmem_cfg->reg_read(sid, 0, randomness, size);
+	add_device_randomness(randomness, size);
+	kfree(randomness);
+
+	platform_set_drvdata(pdev, nvmem);
+
+	return 0;
+}
+
+static const struct sunxi_sid_cfg sun4i_a10_cfg = {
+	.size = 0x10,
+};
+
+static const struct sunxi_sid_cfg sun7i_a20_cfg = {
+	.size = 0x200,
+};
+
+static const struct sunxi_sid_cfg sun8i_h3_cfg = {
+	.value_offset = 0x200,
+	.size = 0x100,
+	.need_register_readout = true,
+};
+
+static const struct sunxi_sid_cfg sun50i_a64_cfg = {
+	.value_offset = 0x200,
+	.size = 0x100,
+};
+
+static const struct sunxi_sid_cfg sun50i_h6_cfg = {
+	.value_offset = 0x200,
+	.size = 0x200,
+};
+
+static const struct of_device_id sunxi_sid_of_match[] = {
+	{ .compatible = "allwinner,sun4i-a10-sid", .data = &sun4i_a10_cfg },
+	{ .compatible = "allwinner,sun7i-a20-sid", .data = &sun7i_a20_cfg },
+	{ .compatible = "allwinner,sun8i-a83t-sid", .data = &sun50i_a64_cfg },
+	{ .compatible = "allwinner,sun8i-h3-sid", .data = &sun8i_h3_cfg },
+	{ .compatible = "allwinner,sun20i-d1-sid", .data = &sun50i_a64_cfg },
+	{ .compatible = "allwinner,sun50i-a64-sid", .data = &sun50i_a64_cfg },
+	{ .compatible = "allwinner,sun50i-h5-sid", .data = &sun50i_a64_cfg },
+	{ .compatible = "allwinner,sun50i-h6-sid", .data = &sun50i_h6_cfg },
+	{/* sentinel */},
+};
+MODULE_DEVICE_TABLE(of, sunxi_sid_of_match);
+
+static struct platform_driver sunxi_sid_driver = {
+	.probe = sunxi_sid_probe,
+	.driver = {
+		.name = "eeprom-sunxi-sid",
+		.of_match_table = sunxi_sid_of_match,
+	},
+};
+module_platform_driver(sunxi_sid_driver);
+
+MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>");
+MODULE_DESCRIPTION("Allwinner sunxi security id driver");
+MODULE_LICENSE("GPL");