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, 118 insertions, 0 deletions

diff --git a/drivers/edac/sifive_edac.c b/drivers/edac/sifive_edac.c
new file mode 100644
index 000000000..a2b193dc6
--- /dev/null
+++ b/drivers/edac/sifive_edac.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * SiFive Platform EDAC Driver
+ *
+ * Copyright (C) 2018-2022 SiFive, Inc.
+ *
+ * This driver is partially based on octeon_edac-pc.c
+ *
+ */
+#include <linux/edac.h>
+#include <linux/platform_device.h>
+#include "edac_module.h"
+#include <soc/sifive/sifive_ccache.h>
+
+#define DRVNAME "sifive_edac"
+
+struct sifive_edac_priv {
+	struct notifier_block notifier;
+	struct edac_device_ctl_info *dci;
+};
+
+/*
+ * EDAC error callback
+ *
+ * @event: non-zero if unrecoverable.
+ */
+static
+int ecc_err_event(struct notifier_block *this, unsigned long event, void *ptr)
+{
+	const char *msg = (char *)ptr;
+	struct sifive_edac_priv *p;
+
+	p = container_of(this, struct sifive_edac_priv, notifier);
+
+	if (event == SIFIVE_CCACHE_ERR_TYPE_UE)
+		edac_device_handle_ue(p->dci, 0, 0, msg);
+	else if (event == SIFIVE_CCACHE_ERR_TYPE_CE)
+		edac_device_handle_ce(p->dci, 0, 0, msg);
+
+	return NOTIFY_OK;
+}
+
+static int ecc_register(struct platform_device *pdev)
+{
+	struct sifive_edac_priv *p;
+
+	p = devm_kzalloc(&pdev->dev, sizeof(*p), GFP_KERNEL);
+	if (!p)
+		return -ENOMEM;
+
+	p->notifier.notifier_call = ecc_err_event;
+	platform_set_drvdata(pdev, p);
+
+	p->dci = edac_device_alloc_ctl_info(0, "sifive_ecc", 1, "sifive_ecc",
+					    1, 1, edac_device_alloc_index());
+	if (!p->dci)
+		return -ENOMEM;
+
+	p->dci->dev = &pdev->dev;
+	p->dci->mod_name = "Sifive ECC Manager";
+	p->dci->ctl_name = dev_name(&pdev->dev);
+	p->dci->dev_name = dev_name(&pdev->dev);
+
+	if (edac_device_add_device(p->dci)) {
+		dev_err(p->dci->dev, "failed to register with EDAC core\n");
+		goto err;
+	}
+
+	register_sifive_ccache_error_notifier(&p->notifier);
+
+	return 0;
+
+err:
+	edac_device_free_ctl_info(p->dci);
+
+	return -ENXIO;
+}
+
+static int ecc_unregister(struct platform_device *pdev)
+{
+	struct sifive_edac_priv *p = platform_get_drvdata(pdev);
+
+	unregister_sifive_ccache_error_notifier(&p->notifier);
+	edac_device_del_device(&pdev->dev);
+	edac_device_free_ctl_info(p->dci);
+
+	return 0;
+}
+
+static struct platform_device *sifive_pdev;
+
+static int __init sifive_edac_init(void)
+{
+	int ret;
+
+	sifive_pdev = platform_device_register_simple(DRVNAME, 0, NULL, 0);
+	if (IS_ERR(sifive_pdev))
+		return PTR_ERR(sifive_pdev);
+
+	ret = ecc_register(sifive_pdev);
+	if (ret)
+		platform_device_unregister(sifive_pdev);
+
+	return ret;
+}
+
+static void __exit sifive_edac_exit(void)
+{
+	ecc_unregister(sifive_pdev);
+	platform_device_unregister(sifive_pdev);
+}
+
+module_init(sifive_edac_init);
+module_exit(sifive_edac_exit);
+
+MODULE_AUTHOR("SiFive Inc.");
+MODULE_DESCRIPTION("SiFive platform EDAC driver");
+MODULE_LICENSE("GPL v2");