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, 225 insertions, 0 deletions

diff --git a/drivers/edac/a72_edac.c b/drivers/edac/a72_edac.c
new file mode 100644
index 000000000..9262d75c3
--- /dev/null
+++ b/drivers/edac/a72_edac.c
@@ -0,0 +1,225 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Cortex A72 EDAC L1 and L2 cache error detection
+ *
+ * Copyright (c) 2020 Pengutronix, Sascha Hauer <s.hauer@pengutronix.de>
+ * Copyright (c) 2025 Microsoft Corporation, <vijayb@linux.microsoft.com>
+ *
+ * Based on Code from:
+ * Copyright (c) 2018, NXP Semiconductor
+ * Author: York Sun <york.sun@nxp.com>
+ */
+
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/bitfield.h>
+#include <asm/smp_plat.h>
+
+#include "edac_module.h"
+
+#define DRVNAME			"a72-edac"
+
+#define SYS_CPUMERRSR_EL1	sys_reg(3, 1, 15, 2, 2)
+#define SYS_L2MERRSR_EL1	sys_reg(3, 1, 15, 2, 3)
+
+#define CPUMERRSR_EL1_RAMID	GENMASK(30, 24)
+#define L2MERRSR_EL1_CPUID_WAY	GENMASK(21, 18)
+
+#define CPUMERRSR_EL1_VALID	BIT(31)
+#define CPUMERRSR_EL1_FATAL	BIT(63)
+#define L2MERRSR_EL1_VALID	BIT(31)
+#define L2MERRSR_EL1_FATAL	BIT(63)
+
+#define L1_I_TAG_RAM		0x00
+#define L1_I_DATA_RAM		0x01
+#define L1_D_TAG_RAM		0x08
+#define L1_D_DATA_RAM		0x09
+#define TLB_RAM			0x18
+
+#define MESSAGE_SIZE		64
+
+struct mem_err_synd_reg {
+	u64 cpu_mesr;
+	u64 l2_mesr;
+};
+
+static struct cpumask compat_mask;
+
+static void report_errors(struct edac_device_ctl_info *edac_ctl, int cpu,
+			  struct mem_err_synd_reg *mesr)
+{
+	u64 cpu_mesr = mesr->cpu_mesr;
+	u64 l2_mesr = mesr->l2_mesr;
+	char msg[MESSAGE_SIZE];
+
+	if (cpu_mesr & CPUMERRSR_EL1_VALID) {
+		const char *str;
+		bool fatal = cpu_mesr & CPUMERRSR_EL1_FATAL;
+
+		switch (FIELD_GET(CPUMERRSR_EL1_RAMID, cpu_mesr)) {
+		case L1_I_TAG_RAM:
+			str = "L1-I Tag RAM";
+			break;
+		case L1_I_DATA_RAM:
+			str = "L1-I Data RAM";
+			break;
+		case L1_D_TAG_RAM:
+			str = "L1-D Tag RAM";
+			break;
+		case L1_D_DATA_RAM:
+			str = "L1-D Data RAM";
+			break;
+		case TLB_RAM:
+			str = "TLB RAM";
+			break;
+		default:
+			str = "Unspecified";
+			break;
+		}
+
+		snprintf(msg, MESSAGE_SIZE, "%s %s error(s) on CPU %d",
+			 str, fatal ? "fatal" : "correctable", cpu);
+
+		if (fatal)
+			edac_device_handle_ue(edac_ctl, cpu, 0, msg);
+		else
+			edac_device_handle_ce(edac_ctl, cpu, 0, msg);
+	}
+
+	if (l2_mesr & L2MERRSR_EL1_VALID) {
+		bool fatal = l2_mesr & L2MERRSR_EL1_FATAL;
+
+		snprintf(msg, MESSAGE_SIZE, "L2 %s error(s) on CPU %d CPUID/WAY 0x%lx",
+			 fatal ? "fatal" : "correctable", cpu,
+			 FIELD_GET(L2MERRSR_EL1_CPUID_WAY, l2_mesr));
+		if (fatal)
+			edac_device_handle_ue(edac_ctl, cpu, 1, msg);
+		else
+			edac_device_handle_ce(edac_ctl, cpu, 1, msg);
+	}
+}
+
+static void read_errors(void *data)
+{
+	struct mem_err_synd_reg *mesr = data;
+
+	mesr->cpu_mesr = read_sysreg_s(SYS_CPUMERRSR_EL1);
+	if (mesr->cpu_mesr & CPUMERRSR_EL1_VALID) {
+		write_sysreg_s(0, SYS_CPUMERRSR_EL1);
+		isb();
+	}
+	mesr->l2_mesr = read_sysreg_s(SYS_L2MERRSR_EL1);
+	if (mesr->l2_mesr & L2MERRSR_EL1_VALID) {
+		write_sysreg_s(0, SYS_L2MERRSR_EL1);
+		isb();
+	}
+}
+
+static void a72_edac_check(struct edac_device_ctl_info *edac_ctl)
+{
+	struct mem_err_synd_reg mesr;
+	int cpu;
+
+	cpus_read_lock();
+	for_each_cpu_and(cpu, cpu_online_mask, &compat_mask) {
+		smp_call_function_single(cpu, read_errors, &mesr, true);
+		report_errors(edac_ctl, cpu, &mesr);
+	}
+	cpus_read_unlock();
+}
+
+static int a72_edac_probe(struct platform_device *pdev)
+{
+	struct edac_device_ctl_info *edac_ctl;
+	struct device *dev = &pdev->dev;
+	int rc;
+
+	edac_ctl = edac_device_alloc_ctl_info(0, "cpu",
+					      num_possible_cpus(), "L", 2, 1,
+					      edac_device_alloc_index());
+	if (!edac_ctl)
+		return -ENOMEM;
+
+	edac_ctl->edac_check = a72_edac_check;
+	edac_ctl->dev = dev;
+	edac_ctl->mod_name = dev_name(dev);
+	edac_ctl->dev_name = dev_name(dev);
+	edac_ctl->ctl_name = DRVNAME;
+	dev_set_drvdata(dev, edac_ctl);
+
+	rc = edac_device_add_device(edac_ctl);
+	if (rc)
+		goto out_dev;
+
+	return 0;
+
+out_dev:
+	edac_device_free_ctl_info(edac_ctl);
+
+	return rc;
+}
+
+static void a72_edac_remove(struct platform_device *pdev)
+{
+	struct edac_device_ctl_info *edac_ctl = dev_get_drvdata(&pdev->dev);
+
+	edac_device_del_device(edac_ctl->dev);
+	edac_device_free_ctl_info(edac_ctl);
+}
+
+static const struct of_device_id cortex_arm64_edac_of_match[] = {
+	{ .compatible = "arm,cortex-a72" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, cortex_arm64_edac_of_match);
+
+static struct platform_driver a72_edac_driver = {
+	.probe = a72_edac_probe,
+	.remove = a72_edac_remove,
+	.driver = {
+		.name = DRVNAME,
+	},
+};
+
+static struct platform_device *a72_pdev;
+
+static int __init a72_edac_driver_init(void)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		struct device_node *np __free(device_node) = of_cpu_device_node_get(cpu);
+		if (np) {
+			if (of_match_node(cortex_arm64_edac_of_match, np) &&
+			    of_property_read_bool(np, "edac-enabled")) {
+				cpumask_set_cpu(cpu, &compat_mask);
+			}
+		} else {
+			pr_warn("failed to find device node for CPU %d\n", cpu);
+		}
+	}
+
+	if (cpumask_empty(&compat_mask))
+		return 0;
+
+	a72_pdev = platform_device_register_simple(DRVNAME, -1, NULL, 0);
+	if (IS_ERR(a72_pdev)) {
+		pr_err("failed to register A72 EDAC device\n");
+		return PTR_ERR(a72_pdev);
+	}
+
+	return platform_driver_register(&a72_edac_driver);
+}
+
+static void __exit a72_edac_driver_exit(void)
+{
+	platform_device_unregister(a72_pdev);
+	platform_driver_unregister(&a72_edac_driver);
+}
+
+module_init(a72_edac_driver_init);
+module_exit(a72_edac_driver_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
+MODULE_DESCRIPTION("Cortex A72 L1 and L2 cache EDAC driver");