iommu/amd: Remove domain->updated

This struct member was used to track whether a domain
change requires updates to the device-table and IOMMU cache
flushes. The problem is, that access to this field is racy
since locking in the common mapping code-paths has been
eliminated.

Move the updated field to the stack to get rid of all
potential races and remove the field from the struct.

Fixes: 92d420e ("iommu/amd: Relax locking in dma_ops path")
Reviewed-by: Filippo Sironi <[email protected]>
Reviewed-by: Jerry Snitselaar <[email protected]>
Signed-off-by: Joerg Roedel <[email protected]>

Author: joergroedel

drivers/iommu/amd_iommu.c

@@ -1458,10 +1458,11 @@ static void free_pagetable(struct protection_domain *domain)
  * another level increases the size of the address space by 9 bits to a size up
  * to 64 bits.
  */
-static void increase_address_space(struct protection_domain *domain,
+static bool increase_address_space(struct protection_domain *domain,
 				   gfp_t gfp)
 {
 	unsigned long flags;
+	bool ret = false;
 	u64 *pte;
 
 	spin_lock_irqsave(&domain->lock, flags);
@@ -1478,27 +1479,29 @@ static void increase_address_space(struct protection_domain *domain,
 					iommu_virt_to_phys(domain->pt_root));
 	domain->pt_root  = pte;
 	domain->mode    += 1;
-	domain->updated  = true;
+
+	ret = true;
 
 out:
 	spin_unlock_irqrestore(&domain->lock, flags);
 
-	return;
+	return ret;
 }
 
 static u64 *alloc_pte(struct protection_domain *domain,
 		      unsigned long address,
 		      unsigned long page_size,
 		      u64 **pte_page,
-		      gfp_t gfp)
+		      gfp_t gfp,
+		      bool *updated)
 {
 	int level, end_lvl;
 	u64 *pte, *page;
 
 	BUG_ON(!is_power_of_2(page_size));
 
 	while (address > PM_LEVEL_SIZE(domain->mode))
-		increase_address_space(domain, gfp);
+		*updated = increase_address_space(domain, gfp) || *updated;
 
 	level   = domain->mode - 1;
 	pte     = &domain->pt_root[PM_LEVEL_INDEX(level, address)];
@@ -1530,7 +1533,7 @@ static u64 *alloc_pte(struct protection_domain *domain,
 			for (i = 0; i < count; ++i)
 				cmpxchg64(&lpte[i], __pte, 0ULL);
 
-			domain->updated = true;
+			*updated = true;
 			continue;
 		}
 
@@ -1547,7 +1550,7 @@ static u64 *alloc_pte(struct protection_domain *domain,
 			if (cmpxchg64(pte, __pte, __npte) != __pte)
 				free_page((unsigned long)page);
 			else if (IOMMU_PTE_PRESENT(__pte))
-				domain->updated = true;
+				*updated = true;
 
 			continue;
 		}
@@ -1656,28 +1659,29 @@ static int iommu_map_page(struct protection_domain *dom,
 			  gfp_t gfp)
 {
 	struct page *freelist = NULL;
+	bool updated = false;
 	u64 __pte, *pte;
-	int i, count;
+	int ret, i, count;
 
 	BUG_ON(!IS_ALIGNED(bus_addr, page_size));
 	BUG_ON(!IS_ALIGNED(phys_addr, page_size));
 
+	ret = -EINVAL;
 	if (!(prot & IOMMU_PROT_MASK))
-		return -EINVAL;
+		goto out;
 
 	count = PAGE_SIZE_PTE_COUNT(page_size);
-	pte   = alloc_pte(dom, bus_addr, page_size, NULL, gfp);
+	pte   = alloc_pte(dom, bus_addr, page_size, NULL, gfp, &updated);
 
-	if (!pte) {
-		update_domain(dom);
-		return -ENOMEM;
-	}
+	ret = -ENOMEM;
+	if (!pte)
+		goto out;
 
 	for (i = 0; i < count; ++i)
 		freelist = free_clear_pte(&pte[i], pte[i], freelist);
 
 	if (freelist != NULL)
-		dom->updated = true;
+		updated = true;
 
 	if (count > 1) {
 		__pte = PAGE_SIZE_PTE(__sme_set(phys_addr), page_size);
@@ -1693,12 +1697,16 @@ static int iommu_map_page(struct protection_domain *dom,
 	for (i = 0; i < count; ++i)
 		pte[i] = __pte;
 
-	update_domain(dom);
+	ret = 0;
+
+out:
+	if (updated)
+		update_domain(dom);
 
 	/* Everything flushed out, free pages now */
 	free_page_list(freelist);
 
-	return 0;
+	return ret;
 }
 
 static unsigned long iommu_unmap_page(struct protection_domain *dom,
@@ -2399,15 +2407,10 @@ static void update_device_table(struct protection_domain *domain)
 
 static void update_domain(struct protection_domain *domain)
 {
-	if (!domain->updated)
-		return;
-
 	update_device_table(domain);
 
 	domain_flush_devices(domain);
 	domain_flush_tlb_pde(domain);
-
-	domain->updated = false;
 }
 
 static int dir2prot(enum dma_data_direction direction)
@@ -3333,7 +3336,6 @@ void amd_iommu_domain_direct_map(struct iommu_domain *dom)
 
 	/* Update data structure */
 	domain->mode    = PAGE_MODE_NONE;
-	domain->updated = true;
 
 	/* Make changes visible to IOMMUs */
 	update_domain(domain);
@@ -3379,7 +3381,6 @@ int amd_iommu_domain_enable_v2(struct iommu_domain *dom, int pasids)
 
 	domain->glx      = levels;
 	domain->flags   |= PD_IOMMUV2_MASK;
-	domain->updated  = true;
 
 	update_domain(domain);
 

drivers/iommu/amd_iommu_types.h

@@ -475,7 +475,6 @@ struct protection_domain {
 	int glx;		/* Number of levels for GCR3 table */
 	u64 *gcr3_tbl;		/* Guest CR3 table */
 	unsigned long flags;	/* flags to find out type of domain */
-	bool updated;		/* complete domain flush required */
 	unsigned dev_cnt;	/* devices assigned to this domain */
 	unsigned dev_iommu[MAX_IOMMUS]; /* per-IOMMU reference count */
 };