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/iommu/amd/pasid.c b/drivers/iommu/amd/pasid.c
new file mode 100644
index 000000000..40be59020
--- /dev/null
+++ b/drivers/iommu/amd/pasid.c
@@ -0,0 +1,203 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024 Advanced Micro Devices, Inc.
+ */
+
+#define pr_fmt(fmt)     "AMD-Vi: " fmt
+#define dev_fmt(fmt)    pr_fmt(fmt)
+
+#include <linux/iommu.h>
+#include <linux/mm_types.h>
+
+#include "amd_iommu.h"
+
+static inline bool is_pasid_enabled(struct iommu_dev_data *dev_data)
+{
+	if (dev_data->pasid_enabled && dev_data->max_pasids &&
+	    dev_data->gcr3_info.gcr3_tbl != NULL)
+		return true;
+
+	return false;
+}
+
+static inline bool is_pasid_valid(struct iommu_dev_data *dev_data,
+				  ioasid_t pasid)
+{
+	if (pasid > 0 && pasid < dev_data->max_pasids)
+		return true;
+
+	return false;
+}
+
+static void remove_dev_pasid(struct pdom_dev_data *pdom_dev_data)
+{
+	/* Update GCR3 table and flush IOTLB */
+	amd_iommu_clear_gcr3(pdom_dev_data->dev_data, pdom_dev_data->pasid);
+
+	list_del(&pdom_dev_data->list);
+	kfree(pdom_dev_data);
+}
+
+/* Clear PASID from device GCR3 table and remove pdom_dev_data from list */
+static void remove_pdom_dev_pasid(struct protection_domain *pdom,
+				  struct device *dev, ioasid_t pasid)
+{
+	struct pdom_dev_data *pdom_dev_data;
+	struct iommu_dev_data *dev_data = dev_iommu_priv_get(dev);
+
+	lockdep_assert_held(&pdom->lock);
+
+	for_each_pdom_dev_data(pdom_dev_data, pdom) {
+		if (pdom_dev_data->dev_data == dev_data &&
+		    pdom_dev_data->pasid == pasid) {
+			remove_dev_pasid(pdom_dev_data);
+			break;
+		}
+	}
+}
+
+static void sva_arch_invalidate_secondary_tlbs(struct mmu_notifier *mn,
+				    struct mm_struct *mm,
+				    unsigned long start, unsigned long end)
+{
+	struct pdom_dev_data *pdom_dev_data;
+	struct protection_domain *sva_pdom;
+	unsigned long flags;
+
+	sva_pdom = container_of(mn, struct protection_domain, mn);
+
+	spin_lock_irqsave(&sva_pdom->lock, flags);
+
+	for_each_pdom_dev_data(pdom_dev_data, sva_pdom) {
+		amd_iommu_dev_flush_pasid_pages(pdom_dev_data->dev_data,
+						pdom_dev_data->pasid,
+						start, end - 1);
+	}
+
+	spin_unlock_irqrestore(&sva_pdom->lock, flags);
+}
+
+static void sva_mn_release(struct mmu_notifier *mn, struct mm_struct *mm)
+{
+	struct pdom_dev_data *pdom_dev_data, *next;
+	struct protection_domain *sva_pdom;
+	unsigned long flags;
+
+	sva_pdom = container_of(mn, struct protection_domain, mn);
+
+	spin_lock_irqsave(&sva_pdom->lock, flags);
+
+	/* Assume dev_data_list contains same PASID with different devices */
+	for_each_pdom_dev_data_safe(pdom_dev_data, next, sva_pdom)
+		remove_dev_pasid(pdom_dev_data);
+
+	spin_unlock_irqrestore(&sva_pdom->lock, flags);
+}
+
+static const struct mmu_notifier_ops sva_mn = {
+	.arch_invalidate_secondary_tlbs = sva_arch_invalidate_secondary_tlbs,
+	.release = sva_mn_release,
+};
+
+static int iommu_sva_set_dev_pasid(struct iommu_domain *domain,
+				   struct device *dev, ioasid_t pasid,
+				   struct iommu_domain *old)
+{
+	struct pdom_dev_data *pdom_dev_data;
+	struct protection_domain *sva_pdom = to_pdomain(domain);
+	struct iommu_dev_data *dev_data = dev_iommu_priv_get(dev);
+	unsigned long flags;
+	int ret = -EINVAL;
+
+	if (old)
+		return -EOPNOTSUPP;
+
+	/* PASID zero is used for requests from the I/O device without PASID */
+	if (!is_pasid_valid(dev_data, pasid))
+		return ret;
+
+	/* Make sure PASID is enabled */
+	if (!is_pasid_enabled(dev_data))
+		return ret;
+
+	/* Add PASID to protection domain pasid list */
+	pdom_dev_data = kzalloc_obj(*pdom_dev_data);
+	if (pdom_dev_data == NULL)
+		return ret;
+
+	pdom_dev_data->pasid = pasid;
+	pdom_dev_data->dev_data = dev_data;
+
+	spin_lock_irqsave(&sva_pdom->lock, flags);
+
+	/* Setup GCR3 table */
+	ret = amd_iommu_set_gcr3(dev_data, pasid,
+				 iommu_virt_to_phys(domain->mm->pgd));
+	if (ret) {
+		kfree(pdom_dev_data);
+		goto out_unlock;
+	}
+
+	list_add(&pdom_dev_data->list, &sva_pdom->dev_data_list);
+
+out_unlock:
+	spin_unlock_irqrestore(&sva_pdom->lock, flags);
+	return ret;
+}
+
+void amd_iommu_remove_dev_pasid(struct device *dev, ioasid_t pasid,
+				struct iommu_domain *domain)
+{
+	struct protection_domain *sva_pdom;
+	unsigned long flags;
+
+	if (!is_pasid_valid(dev_iommu_priv_get(dev), pasid))
+		return;
+
+	sva_pdom = to_pdomain(domain);
+
+	spin_lock_irqsave(&sva_pdom->lock, flags);
+
+	/* Remove PASID from dev_data_list */
+	remove_pdom_dev_pasid(sva_pdom, dev, pasid);
+
+	spin_unlock_irqrestore(&sva_pdom->lock, flags);
+}
+
+static void iommu_sva_domain_free(struct iommu_domain *domain)
+{
+	struct protection_domain *sva_pdom = to_pdomain(domain);
+
+	if (sva_pdom->mn.ops)
+		mmu_notifier_unregister(&sva_pdom->mn, domain->mm);
+
+	amd_iommu_domain_free(domain);
+}
+
+static const struct iommu_domain_ops amd_sva_domain_ops = {
+	.set_dev_pasid = iommu_sva_set_dev_pasid,
+	.free	       = iommu_sva_domain_free
+};
+
+struct iommu_domain *amd_iommu_domain_alloc_sva(struct device *dev,
+						struct mm_struct *mm)
+{
+	struct protection_domain *pdom;
+	int ret;
+
+	pdom = protection_domain_alloc();
+	if (!pdom)
+		return ERR_PTR(-ENOMEM);
+
+	pdom->domain.ops = &amd_sva_domain_ops;
+	pdom->mn.ops = &sva_mn;
+	pdom->domain.type = IOMMU_DOMAIN_SVA;
+
+	ret = mmu_notifier_register(&pdom->mn, mm);
+	if (ret) {
+		amd_iommu_domain_free(&pdom->domain);
+		return ERR_PTR(ret);
+	}
+
+	return &pdom->domain;
+}