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, 164 insertions, 0 deletions

diff --git a/drivers/iommu/intel/perf.c b/drivers/iommu/intel/perf.c
new file mode 100644
index 000000000..bec98dcbb
--- /dev/null
+++ b/drivers/iommu/intel/perf.c
@@ -0,0 +1,164 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * perf.c - performance monitor
+ *
+ * Copyright (C) 2021 Intel Corporation
+ *
+ * Author: Lu Baolu <baolu.lu@linux.intel.com>
+ *         Fenghua Yu <fenghua.yu@intel.com>
+ */
+
+#include <linux/spinlock.h>
+
+#include "iommu.h"
+#include "perf.h"
+
+static DEFINE_SPINLOCK(latency_lock);
+
+bool dmar_latency_enabled(struct intel_iommu *iommu, enum latency_type type)
+{
+	struct latency_statistic *lstat = iommu->perf_statistic;
+
+	return lstat && lstat[type].enabled;
+}
+
+int dmar_latency_enable(struct intel_iommu *iommu, enum latency_type type)
+{
+	struct latency_statistic *lstat;
+	unsigned long flags;
+	int ret = -EBUSY;
+
+	if (dmar_latency_enabled(iommu, type))
+		return 0;
+
+	spin_lock_irqsave(&latency_lock, flags);
+	if (!iommu->perf_statistic) {
+		iommu->perf_statistic = kzalloc_objs(*lstat, DMAR_LATENCY_NUM,
+						     GFP_ATOMIC);
+		if (!iommu->perf_statistic) {
+			ret = -ENOMEM;
+			goto unlock_out;
+		}
+	}
+
+	lstat = iommu->perf_statistic;
+
+	if (!lstat[type].enabled) {
+		lstat[type].enabled = true;
+		lstat[type].counter[COUNTS_MIN] = UINT_MAX;
+		ret = 0;
+	}
+unlock_out:
+	spin_unlock_irqrestore(&latency_lock, flags);
+
+	return ret;
+}
+
+void dmar_latency_disable(struct intel_iommu *iommu, enum latency_type type)
+{
+	struct latency_statistic *lstat = iommu->perf_statistic;
+	unsigned long flags;
+
+	if (!dmar_latency_enabled(iommu, type))
+		return;
+
+	spin_lock_irqsave(&latency_lock, flags);
+	memset(&lstat[type], 0, sizeof(*lstat));
+	spin_unlock_irqrestore(&latency_lock, flags);
+}
+
+void dmar_latency_update(struct intel_iommu *iommu, enum latency_type type, u64 latency)
+{
+	struct latency_statistic *lstat = iommu->perf_statistic;
+	unsigned long flags;
+	u64 min, max;
+
+	if (!dmar_latency_enabled(iommu, type))
+		return;
+
+	spin_lock_irqsave(&latency_lock, flags);
+	if (latency < 100)
+		lstat[type].counter[COUNTS_10e2]++;
+	else if (latency < 1000)
+		lstat[type].counter[COUNTS_10e3]++;
+	else if (latency < 10000)
+		lstat[type].counter[COUNTS_10e4]++;
+	else if (latency < 100000)
+		lstat[type].counter[COUNTS_10e5]++;
+	else if (latency < 1000000)
+		lstat[type].counter[COUNTS_10e6]++;
+	else if (latency < 10000000)
+		lstat[type].counter[COUNTS_10e7]++;
+	else
+		lstat[type].counter[COUNTS_10e8_plus]++;
+
+	min = lstat[type].counter[COUNTS_MIN];
+	max = lstat[type].counter[COUNTS_MAX];
+	lstat[type].counter[COUNTS_MIN] = min_t(u64, min, latency);
+	lstat[type].counter[COUNTS_MAX] = max_t(u64, max, latency);
+	lstat[type].counter[COUNTS_SUM] += latency;
+	lstat[type].samples++;
+	spin_unlock_irqrestore(&latency_lock, flags);
+}
+
+static char *latency_counter_names[] = {
+	"                  <0.1us",
+	"   0.1us-1us", "    1us-10us", "  10us-100us",
+	"   100us-1ms", "    1ms-10ms", "      >=10ms",
+	"     min(us)", "     max(us)", " average(us)"
+};
+
+static char *latency_type_names[] = {
+	"   inv_iotlb", "  inv_devtlb", "     inv_iec",
+	"     svm_prq"
+};
+
+void dmar_latency_snapshot(struct intel_iommu *iommu, char *str, size_t size)
+{
+	struct latency_statistic *lstat = iommu->perf_statistic;
+	unsigned long flags;
+	int bytes = 0, i, j;
+
+	memset(str, 0, size);
+
+	for (i = 0; i < COUNTS_NUM; i++)
+		bytes += scnprintf(str + bytes, size - bytes,
+				  "%s", latency_counter_names[i]);
+
+	spin_lock_irqsave(&latency_lock, flags);
+	for (i = 0; i < DMAR_LATENCY_NUM; i++) {
+		if (!dmar_latency_enabled(iommu, i))
+			continue;
+
+		bytes += scnprintf(str + bytes, size - bytes,
+				  "\n%s", latency_type_names[i]);
+
+		for (j = 0; j < COUNTS_NUM; j++) {
+			u64 val = lstat[i].counter[j];
+
+			switch (j) {
+			case COUNTS_MIN:
+				if (val == UINT_MAX)
+					val = 0;
+				else
+					val = div_u64(val, 1000);
+				break;
+			case COUNTS_MAX:
+				val = div_u64(val, 1000);
+				break;
+			case COUNTS_SUM:
+				if (lstat[i].samples)
+					val = div_u64(val, (lstat[i].samples * 1000));
+				else
+					val = 0;
+				break;
+			default:
+				break;
+			}
+
+			bytes += scnprintf(str + bytes, size - bytes,
+					  "%12lld", val);
+		}
+	}
+	spin_unlock_irqrestore(&latency_lock, flags);
+}