linux-kernel - [PATCH 1/1] iommu/vt-d: Use second level for GPA->HPA translation

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Date:   Fri, 24 Sep 2021 10:29:31 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     Kevin Tian <kevin.tian@...el.com>, Ashok Raj <ashok.raj@...el.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Lu Baolu <baolu.lu@...ux.intel.com>
Subject: [PATCH 1/1] iommu/vt-d: Use second level for GPA->HPA translation

The IOMMU VT-d implementation uses the first level for GPA->HPA translation
by default. Although both the first level and the second level could handle
the DMA translation, they are different in some way. For example, the second
level translation has separate controls for the Access/Dirty page tracking
and the page-level forcing snoop. With first level translation, there're
no such controls. This uses the second level for GPA->HPA translation so
that it could provide a consistent hardware interface for use cases like
dirty page tracking during the VM live migration.

Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
---
 include/linux/intel-iommu.h |  7 ++-----
 drivers/iommu/intel/iommu.c | 21 +++++++++++++--------
 2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
index 05a65eb155f7..a5fb20702201 100644
--- a/include/linux/intel-iommu.h
+++ b/include/linux/intel-iommu.h
@@ -517,22 +517,19 @@ struct context_entry {
 	u64 hi;
 };
 
-/* si_domain contains mulitple devices */
-#define DOMAIN_FLAG_STATIC_IDENTITY		BIT(0)
-
 /*
  * When VT-d works in the scalable mode, it allows DMA translation to
  * happen through either first level or second level page table. This
  * bit marks that the DMA translation for the domain goes through the
  * first level page table, otherwise, it goes through the second level.
  */
-#define DOMAIN_FLAG_USE_FIRST_LEVEL		BIT(1)
+#define DOMAIN_FLAG_USE_FIRST_LEVEL		BIT(0)
 
 /*
  * Domain represents a virtual machine which demands iommu nested
  * translation mode support.
  */
-#define DOMAIN_FLAG_NESTING_MODE		BIT(2)
+#define DOMAIN_FLAG_NESTING_MODE		BIT(1)
 
 struct dmar_domain {
 	int	nid;			/* node id */
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index d75f59ae28e6..c814fea0522e 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -522,7 +522,7 @@ static inline void free_devinfo_mem(void *vaddr)
 
 static inline int domain_type_is_si(struct dmar_domain *domain)
 {
-	return domain->flags & DOMAIN_FLAG_STATIC_IDENTITY;
+	return domain->domain.type == IOMMU_DOMAIN_IDENTITY;
 }
 
 static inline bool domain_use_first_level(struct dmar_domain *domain)
@@ -1874,12 +1874,18 @@ static void free_dmar_iommu(struct intel_iommu *iommu)
  * Check and return whether first level is used by default for
  * DMA translation.
  */
-static bool first_level_by_default(void)
+static bool first_level_by_default(unsigned int type)
 {
-	return scalable_mode_support() && intel_cap_flts_sanity();
+	if (type == IOMMU_DOMAIN_UNMANAGED)
+		return false;
+
+	if (!scalable_mode_support() || !intel_cap_flts_sanity())
+		return false;
+
+	return true;
 }
 
-static struct dmar_domain *alloc_domain(int flags)
+static struct dmar_domain *alloc_domain(unsigned int type)
 {
 	struct dmar_domain *domain;
 
@@ -1889,8 +1895,7 @@ static struct dmar_domain *alloc_domain(int flags)
 
 	memset(domain, 0, sizeof(*domain));
 	domain->nid = NUMA_NO_NODE;
-	domain->flags = flags;
-	if (first_level_by_default())
+	if (first_level_by_default(type))
 		domain->flags |= DOMAIN_FLAG_USE_FIRST_LEVEL;
 	domain->has_iotlb_device = false;
 	INIT_LIST_HEAD(&domain->devices);
@@ -2708,7 +2713,7 @@ static int __init si_domain_init(int hw)
 	struct device *dev;
 	int i, nid, ret;
 
-	si_domain = alloc_domain(DOMAIN_FLAG_STATIC_IDENTITY);
+	si_domain = alloc_domain(IOMMU_DOMAIN_IDENTITY);
 	if (!si_domain)
 		return -EFAULT;
 
@@ -4517,7 +4522,7 @@ static struct iommu_domain *intel_iommu_domain_alloc(unsigned type)
 	case IOMMU_DOMAIN_DMA:
 	case IOMMU_DOMAIN_DMA_FQ:
 	case IOMMU_DOMAIN_UNMANAGED:
-		dmar_domain = alloc_domain(0);
+		dmar_domain = alloc_domain(type);
 		if (!dmar_domain) {
 			pr_err("Can't allocate dmar_domain\n");
 			return NULL;
-- 
2.25.1