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, 77 insertions, 0 deletions

diff --git a/drivers/edac/layerscape_edac.c b/drivers/edac/layerscape_edac.c
new file mode 100644
index 000000000..a2caa7fc5
--- /dev/null
+++ b/drivers/edac/layerscape_edac.c
@@ -0,0 +1,77 @@
+/*
+ * Freescale Memory Controller kernel module
+ *
+ * Author: York Sun <york.sun@nxp.com>
+ *
+ * Copyright 2016 NXP Semiconductor
+ *
+ * Derived from mpc85xx_edac.c
+ * Author: Dave Jiang <djiang@mvista.com>
+ *
+ * 2006-2007 (c) MontaVista Software, Inc. This file is licensed under
+ * the terms of the GNU General Public License version 2. This program
+ * is licensed "as is" without any warranty of any kind, whether express
+ * or implied.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include "edac_module.h"
+#include "fsl_ddr_edac.h"
+
+static const struct of_device_id fsl_ddr_mc_err_of_match[] = {
+	{ .compatible = "fsl,qoriq-memory-controller", },
+	{ .compatible = "nxp,imx9-memory-controller", .data = (void *)TYPE_IMX9, },
+	{},
+};
+MODULE_DEVICE_TABLE(of, fsl_ddr_mc_err_of_match);
+
+static struct platform_driver fsl_ddr_mc_err_driver = {
+	.probe = fsl_mc_err_probe,
+	.remove = fsl_mc_err_remove,
+	.driver = {
+		.name = "fsl_ddr_mc_err",
+		.of_match_table = fsl_ddr_mc_err_of_match,
+	},
+};
+
+static int __init fsl_ddr_mc_init(void)
+{
+	int res;
+
+	if (ghes_get_devices())
+		return -EBUSY;
+
+	/* make sure error reporting method is sane */
+	switch (edac_op_state) {
+	case EDAC_OPSTATE_POLL:
+	case EDAC_OPSTATE_INT:
+		break;
+	default:
+		edac_op_state = EDAC_OPSTATE_INT;
+		break;
+	}
+
+	res = platform_driver_register(&fsl_ddr_mc_err_driver);
+	if (res) {
+		pr_err("MC fails to register\n");
+		return res;
+	}
+
+	return 0;
+}
+
+module_init(fsl_ddr_mc_init);
+
+static void __exit fsl_ddr_mc_exit(void)
+{
+	platform_driver_unregister(&fsl_ddr_mc_err_driver);
+}
+
+module_exit(fsl_ddr_mc_exit);
+
+MODULE_DESCRIPTION("Freescale Layerscape EDAC driver");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("NXP Semiconductor");
+module_param(edac_op_state, int, 0444);
+MODULE_PARM_DESC(edac_op_state, "EDAC Error Reporting state: 0=Poll, 2=Interrupt");