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, 203 insertions, 0 deletions

diff --git a/drivers/mfd/altera-sysmgr.c b/drivers/mfd/altera-sysmgr.c
new file mode 100644
index 000000000..90c6902d5
--- /dev/null
+++ b/drivers/mfd/altera-sysmgr.c
@@ -0,0 +1,203 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Copyright (C) 2018-2019, Intel Corporation.
+ *  Copyright (C) 2012 Freescale Semiconductor, Inc.
+ *  Copyright (C) 2012 Linaro Ltd.
+ *
+ *  Based on syscon driver.
+ */
+
+#include <linux/arm-smccc.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/mfd/altera-sysmgr.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+/**
+ * struct altr_sysmgr - Altera SOCFPGA System Manager
+ * @regmap: the regmap used for System Manager accesses.
+ */
+struct altr_sysmgr {
+	struct regmap   *regmap;
+};
+
+static struct platform_driver altr_sysmgr_driver;
+
+/**
+ * s10_protected_reg_write
+ * Write to a protected SMC register.
+ * @base: Base address of System Manager
+ * @reg:  Address offset of register
+ * @val:  Value to write
+ * Return: INTEL_SIP_SMC_STATUS_OK (0) on success
+ *	   INTEL_SIP_SMC_REG_ERROR on error
+ *	   INTEL_SIP_SMC_RETURN_UNKNOWN_FUNCTION if not supported
+ */
+static int s10_protected_reg_write(void *base,
+				   unsigned int reg, unsigned int val)
+{
+	struct arm_smccc_res result;
+	unsigned long sysmgr_base = (unsigned long)base;
+
+	arm_smccc_smc(INTEL_SIP_SMC_REG_WRITE, sysmgr_base + reg,
+		      val, 0, 0, 0, 0, 0, &result);
+
+	return (int)result.a0;
+}
+
+/**
+ * s10_protected_reg_read
+ * Read the status of a protected SMC register
+ * @base: Base address of System Manager.
+ * @reg:  Address of register
+ * @val:  Value read.
+ * Return: INTEL_SIP_SMC_STATUS_OK (0) on success
+ *	   INTEL_SIP_SMC_REG_ERROR on error
+ *	   INTEL_SIP_SMC_RETURN_UNKNOWN_FUNCTION if not supported
+ */
+static int s10_protected_reg_read(void *base,
+				  unsigned int reg, unsigned int *val)
+{
+	struct arm_smccc_res result;
+	unsigned long sysmgr_base = (unsigned long)base;
+
+	arm_smccc_smc(INTEL_SIP_SMC_REG_READ, sysmgr_base + reg,
+		      0, 0, 0, 0, 0, 0, &result);
+
+	*val = (unsigned int)result.a1;
+
+	return (int)result.a0;
+}
+
+static struct regmap_config altr_sysmgr_regmap_cfg = {
+	.name = "altr_sysmgr",
+	.reg_bits = 32,
+	.reg_stride = 4,
+	.val_bits = 32,
+	.fast_io = true,
+	.use_single_read = true,
+	.use_single_write = true,
+};
+
+/**
+ * altr_sysmgr_regmap_lookup_by_phandle
+ * Find the sysmgr previous configured in probe() and return regmap property.
+ * Return: regmap if found or error if not found.
+ *
+ * @np: Pointer to device's Device Tree node
+ * @property: Device Tree property name which references the sysmgr
+ */
+struct regmap *altr_sysmgr_regmap_lookup_by_phandle(struct device_node *np,
+						    const char *property)
+{
+	struct device *dev;
+	struct altr_sysmgr *sysmgr;
+	struct device_node *sysmgr_np;
+
+	if (property)
+		sysmgr_np = of_parse_phandle(np, property, 0);
+	else
+		sysmgr_np = np;
+
+	if (!sysmgr_np)
+		return ERR_PTR(-ENODEV);
+
+	dev = driver_find_device_by_of_node(&altr_sysmgr_driver.driver,
+					    (void *)sysmgr_np);
+	if (property)
+		of_node_put(sysmgr_np);
+
+	if (!dev)
+		return ERR_PTR(-EPROBE_DEFER);
+
+	sysmgr = dev_get_drvdata(dev);
+
+	put_device(dev);
+
+	return sysmgr->regmap;
+}
+EXPORT_SYMBOL_GPL(altr_sysmgr_regmap_lookup_by_phandle);
+
+static int sysmgr_probe(struct platform_device *pdev)
+{
+	struct altr_sysmgr *sysmgr;
+	struct regmap *regmap;
+	struct resource *res;
+	struct regmap_config sysmgr_config = altr_sysmgr_regmap_cfg;
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	void __iomem *base;
+
+	sysmgr = devm_kzalloc(dev, sizeof(*sysmgr), GFP_KERNEL);
+	if (!sysmgr)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENOENT;
+
+	sysmgr_config.max_register = resource_size(res) -
+				     sysmgr_config.reg_stride;
+	if (of_device_is_compatible(np, "altr,sys-mgr-s10")) {
+		sysmgr_config.reg_read = s10_protected_reg_read;
+		sysmgr_config.reg_write = s10_protected_reg_write;
+
+		/* Need physical address for SMCC call */
+		regmap = devm_regmap_init(dev, NULL,
+					  (void *)(uintptr_t)res->start,
+					  &sysmgr_config);
+	} else {
+		base = devm_ioremap(dev, res->start, resource_size(res));
+		if (!base)
+			return -ENOMEM;
+
+		sysmgr_config.max_register = resource_size(res) - 4;
+		regmap = devm_regmap_init_mmio(dev, base, &sysmgr_config);
+	}
+
+	if (IS_ERR(regmap)) {
+		pr_err("regmap init failed\n");
+		return PTR_ERR(regmap);
+	}
+
+	sysmgr->regmap = regmap;
+
+	platform_set_drvdata(pdev, sysmgr);
+
+	return 0;
+}
+
+static const struct of_device_id altr_sysmgr_of_match[] = {
+	{ .compatible = "altr,sys-mgr" },
+	{ .compatible = "altr,sys-mgr-s10" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, altr_sysmgr_of_match);
+
+static struct platform_driver altr_sysmgr_driver = {
+	.probe =  sysmgr_probe,
+	.driver = {
+		.name = "altr,system_manager",
+		.of_match_table = altr_sysmgr_of_match,
+	},
+};
+
+static int __init altr_sysmgr_init(void)
+{
+	return platform_driver_register(&altr_sysmgr_driver);
+}
+core_initcall(altr_sysmgr_init);
+
+static void __exit altr_sysmgr_exit(void)
+{
+	platform_driver_unregister(&altr_sysmgr_driver);
+}
+module_exit(altr_sysmgr_exit);
+
+MODULE_AUTHOR("Thor Thayer <>");
+MODULE_DESCRIPTION("SOCFPGA System Manager driver");