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, 142 insertions, 0 deletions

diff --git a/drivers/nvmem/rcar-efuse.c b/drivers/nvmem/rcar-efuse.c
new file mode 100644
index 000000000..b94ff83b7
--- /dev/null
+++ b/drivers/nvmem/rcar-efuse.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Renesas R-Car E-FUSE/OTP Driver
+ *
+ * Copyright (C) 2024 Glider bv
+ */
+
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/io.h>
+#include <linux/nvmem-provider.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/property.h>
+
+struct rcar_fuse {
+	struct nvmem_keepout keepouts[2];
+	struct nvmem_device *nvmem;
+	struct device *dev;
+	void __iomem *base;
+};
+
+struct rcar_fuse_data {
+	unsigned int bank;	/* 0: PFC + E-FUSE, 1: OPT_MEM + E-FUSE */
+	unsigned int start;	/* inclusive */
+	unsigned int end;	/* exclusive */
+};
+
+static int rcar_fuse_reg_read(void *priv, unsigned int offset, void *val,
+			      size_t bytes)
+{
+	struct rcar_fuse *fuse = priv;
+	int ret;
+
+	ret = pm_runtime_resume_and_get(fuse->dev);
+	if (ret < 0)
+		return ret;
+
+	__ioread32_copy(val, fuse->base + offset, bytes / 4);
+
+	pm_runtime_put(fuse->dev);
+
+	return 0;
+}
+
+static int rcar_fuse_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	const struct rcar_fuse_data *data = device_get_match_data(dev);
+	struct nvmem_config config = {
+		.dev = dev,
+		.name = "rcar-fuse",
+		.id = NVMEM_DEVID_NONE,
+		.owner = THIS_MODULE,
+		.type = NVMEM_TYPE_OTP,
+		.read_only = true,
+		.root_only = true,
+		.reg_read = rcar_fuse_reg_read,
+		.word_size = 4,
+		.stride = 4,
+	};
+	struct rcar_fuse *fuse;
+	struct resource *res;
+	int ret;
+
+	ret = devm_pm_runtime_enable(dev);
+	if (ret < 0)
+		return ret;
+
+	fuse = devm_kzalloc(dev, sizeof(*fuse), GFP_KERNEL);
+	if (!fuse)
+		return -ENOMEM;
+
+	fuse->base = devm_platform_get_and_ioremap_resource(pdev, data->bank,
+							    &res);
+	if (IS_ERR(fuse->base))
+		return PTR_ERR(fuse->base);
+
+	fuse->dev = dev;
+	fuse->keepouts[0].start = 0;
+	fuse->keepouts[0].end = data->start;
+	fuse->keepouts[1].start = data->end;
+	fuse->keepouts[1].end = resource_size(res);
+
+	config.keepout = fuse->keepouts;
+	config.nkeepout = ARRAY_SIZE(fuse->keepouts);
+	config.size = resource_size(res);
+	config.priv = fuse;
+
+	fuse->nvmem = devm_nvmem_register(dev, &config);
+	if (IS_ERR(fuse->nvmem))
+		return dev_err_probe(dev, PTR_ERR(fuse->nvmem),
+				     "Failed to register NVMEM device\n");
+
+	return 0;
+}
+
+static const struct rcar_fuse_data rcar_fuse_v3u = {
+	.bank = 0,
+	.start = 0x0c0,
+	.end = 0x0e8,
+};
+
+static const struct rcar_fuse_data rcar_fuse_s4 = {
+	.bank = 0,
+	.start = 0x0c0,
+	.end = 0x14c,
+};
+
+static const struct rcar_fuse_data rcar_fuse_v4h = {
+	.bank = 1,
+	.start = 0x100,
+	.end = 0x1a0,
+};
+
+static const struct rcar_fuse_data rcar_fuse_v4m = {
+	.bank = 1,
+	.start = 0x100,
+	.end = 0x110,
+};
+
+static const struct of_device_id rcar_fuse_match[] = {
+	{ .compatible = "renesas,r8a779a0-efuse", .data = &rcar_fuse_v3u },
+	{ .compatible = "renesas,r8a779f0-efuse", .data = &rcar_fuse_s4 },
+	{ .compatible = "renesas,r8a779g0-otp", .data = &rcar_fuse_v4h },
+	{ .compatible = "renesas,r8a779h0-otp", .data = &rcar_fuse_v4m },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, rcar_fuse_match);
+
+static struct platform_driver rcar_fuse_driver = {
+	.probe = rcar_fuse_probe,
+	.driver = {
+		.name = "rcar_fuse",
+		.of_match_table = rcar_fuse_match,
+	},
+};
+module_platform_driver(rcar_fuse_driver);
+
+MODULE_DESCRIPTION("Renesas R-Car E-FUSE/OTP driver");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Geert Uytterhoeven");