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, 241 insertions, 0 deletions

diff --git a/drivers/iommu/intel/nested.c b/drivers/iommu/intel/nested.c
new file mode 100644
index 000000000..2b979bec5
--- /dev/null
+++ b/drivers/iommu/intel/nested.c
@@ -0,0 +1,241 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * nested.c - nested mode translation support
+ *
+ * Copyright (C) 2023 Intel Corporation
+ *
+ * Author: Lu Baolu <baolu.lu@linux.intel.com>
+ *         Jacob Pan <jacob.jun.pan@linux.intel.com>
+ *         Yi Liu <yi.l.liu@intel.com>
+ */
+
+#define pr_fmt(fmt)	"DMAR: " fmt
+
+#include <linux/iommu.h>
+#include <linux/pci.h>
+#include <linux/pci-ats.h>
+
+#include "iommu.h"
+#include "pasid.h"
+
+static int intel_nested_attach_dev(struct iommu_domain *domain,
+				   struct device *dev, struct iommu_domain *old)
+{
+	struct device_domain_info *info = dev_iommu_priv_get(dev);
+	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
+	struct intel_iommu *iommu = info->iommu;
+	unsigned long flags;
+	int ret = 0;
+
+	device_block_translation(dev);
+
+	/*
+	 * Stage-1 domain cannot work alone, it is nested on a s2_domain.
+	 * The s2_domain will be used in nested translation, hence needs
+	 * to ensure the s2_domain is compatible with this IOMMU.
+	 */
+	ret = paging_domain_compatible(&dmar_domain->s2_domain->domain, dev);
+	if (ret) {
+		dev_err_ratelimited(dev, "s2 domain is not compatible\n");
+		return ret;
+	}
+
+	ret = domain_attach_iommu(dmar_domain, iommu);
+	if (ret) {
+		dev_err_ratelimited(dev, "Failed to attach domain to iommu\n");
+		return ret;
+	}
+
+	ret = cache_tag_assign_domain(dmar_domain, dev, IOMMU_NO_PASID);
+	if (ret)
+		goto detach_iommu;
+
+	ret = iopf_for_domain_set(domain, dev);
+	if (ret)
+		goto unassign_tag;
+
+	ret = intel_pasid_setup_nested(iommu, dev,
+				       IOMMU_NO_PASID, dmar_domain);
+	if (ret)
+		goto disable_iopf;
+
+	info->domain = dmar_domain;
+	info->domain_attached = true;
+	spin_lock_irqsave(&dmar_domain->lock, flags);
+	list_add(&info->link, &dmar_domain->devices);
+	spin_unlock_irqrestore(&dmar_domain->lock, flags);
+
+	return 0;
+disable_iopf:
+	iopf_for_domain_remove(domain, dev);
+unassign_tag:
+	cache_tag_unassign_domain(dmar_domain, dev, IOMMU_NO_PASID);
+detach_iommu:
+	domain_detach_iommu(dmar_domain, iommu);
+
+	return ret;
+}
+
+static void intel_nested_domain_free(struct iommu_domain *domain)
+{
+	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
+	struct dmar_domain *s2_domain = dmar_domain->s2_domain;
+
+	spin_lock(&s2_domain->s1_lock);
+	list_del(&dmar_domain->s2_link);
+	spin_unlock(&s2_domain->s1_lock);
+	kfree(dmar_domain->qi_batch);
+	kfree(dmar_domain);
+}
+
+static int intel_nested_cache_invalidate_user(struct iommu_domain *domain,
+					      struct iommu_user_data_array *array)
+{
+	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
+	struct iommu_hwpt_vtd_s1_invalidate inv_entry;
+	u32 index, processed = 0;
+	int ret = 0;
+
+	if (array->type != IOMMU_HWPT_INVALIDATE_DATA_VTD_S1) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	for (index = 0; index < array->entry_num; index++) {
+		ret = iommu_copy_struct_from_user_array(&inv_entry, array,
+							IOMMU_HWPT_INVALIDATE_DATA_VTD_S1,
+							index, __reserved);
+		if (ret)
+			break;
+
+		if ((inv_entry.flags & ~IOMMU_VTD_INV_FLAGS_LEAF) ||
+		    inv_entry.__reserved) {
+			ret = -EOPNOTSUPP;
+			break;
+		}
+
+		if (!IS_ALIGNED(inv_entry.addr, VTD_PAGE_SIZE) ||
+		    ((inv_entry.npages == U64_MAX) && inv_entry.addr)) {
+			ret = -EINVAL;
+			break;
+		}
+
+		cache_tag_flush_range(dmar_domain, inv_entry.addr,
+				      inv_entry.addr + nrpages_to_size(inv_entry.npages) - 1,
+				      inv_entry.flags & IOMMU_VTD_INV_FLAGS_LEAF);
+		processed++;
+	}
+
+out:
+	array->entry_num = processed;
+	return ret;
+}
+
+static int domain_setup_nested(struct intel_iommu *iommu,
+			       struct dmar_domain *domain,
+			       struct device *dev, ioasid_t pasid,
+			       struct iommu_domain *old)
+{
+	if (old)
+		intel_pasid_tear_down_entry(iommu, dev, pasid, false);
+
+	return intel_pasid_setup_nested(iommu, dev, pasid, domain);
+}
+
+static int intel_nested_set_dev_pasid(struct iommu_domain *domain,
+				      struct device *dev, ioasid_t pasid,
+				      struct iommu_domain *old)
+{
+	struct device_domain_info *info = dev_iommu_priv_get(dev);
+	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
+	struct intel_iommu *iommu = info->iommu;
+	struct dev_pasid_info *dev_pasid;
+	int ret;
+
+	if (!pasid_supported(iommu) || dev_is_real_dma_subdevice(dev))
+		return -EOPNOTSUPP;
+
+	if (context_copied(iommu, info->bus, info->devfn))
+		return -EBUSY;
+
+	ret = paging_domain_compatible(&dmar_domain->s2_domain->domain, dev);
+	if (ret)
+		return ret;
+
+	dev_pasid = domain_add_dev_pasid(domain, dev, pasid);
+	if (IS_ERR(dev_pasid))
+		return PTR_ERR(dev_pasid);
+
+	ret = iopf_for_domain_replace(domain, old, dev);
+	if (ret)
+		goto out_remove_dev_pasid;
+
+	ret = domain_setup_nested(iommu, dmar_domain, dev, pasid, old);
+	if (ret)
+		goto out_unwind_iopf;
+
+	domain_remove_dev_pasid(old, dev, pasid);
+
+	return 0;
+
+out_unwind_iopf:
+	iopf_for_domain_replace(old, domain, dev);
+out_remove_dev_pasid:
+	domain_remove_dev_pasid(domain, dev, pasid);
+	return ret;
+}
+
+static const struct iommu_domain_ops intel_nested_domain_ops = {
+	.attach_dev		= intel_nested_attach_dev,
+	.set_dev_pasid		= intel_nested_set_dev_pasid,
+	.free			= intel_nested_domain_free,
+	.cache_invalidate_user	= intel_nested_cache_invalidate_user,
+};
+
+struct iommu_domain *
+intel_iommu_domain_alloc_nested(struct device *dev, struct iommu_domain *parent,
+				u32 flags,
+				const struct iommu_user_data *user_data)
+{
+	struct device_domain_info *info = dev_iommu_priv_get(dev);
+	struct dmar_domain *s2_domain = to_dmar_domain(parent);
+	struct intel_iommu *iommu = info->iommu;
+	struct iommu_hwpt_vtd_s1 vtd;
+	struct dmar_domain *domain;
+	int ret;
+
+	if (!nested_supported(iommu) || flags & ~IOMMU_HWPT_ALLOC_PASID)
+		return ERR_PTR(-EOPNOTSUPP);
+
+	/* Must be nested domain */
+	if (user_data->type != IOMMU_HWPT_DATA_VTD_S1)
+		return ERR_PTR(-EOPNOTSUPP);
+	if (!intel_domain_is_ss_paging(s2_domain) || !s2_domain->nested_parent)
+		return ERR_PTR(-EINVAL);
+
+	ret = iommu_copy_struct_from_user(&vtd, user_data,
+					  IOMMU_HWPT_DATA_VTD_S1, __reserved);
+	if (ret)
+		return ERR_PTR(ret);
+
+	domain = kzalloc_obj(*domain, GFP_KERNEL_ACCOUNT);
+	if (!domain)
+		return ERR_PTR(-ENOMEM);
+
+	domain->s2_domain = s2_domain;
+	domain->s1_cfg = vtd;
+	domain->domain.ops = &intel_nested_domain_ops;
+	domain->domain.type = IOMMU_DOMAIN_NESTED;
+	INIT_LIST_HEAD(&domain->devices);
+	INIT_LIST_HEAD(&domain->dev_pasids);
+	INIT_LIST_HEAD(&domain->cache_tags);
+	spin_lock_init(&domain->lock);
+	spin_lock_init(&domain->cache_lock);
+	xa_init(&domain->iommu_array);
+
+	spin_lock(&s2_domain->s1_lock);
+	list_add(&domain->s2_link, &s2_domain->s1_domains);
+	spin_unlock(&s2_domain->s1_lock);
+
+	return &domain->domain;
+}