linux-kernel - [RFC 2/3] iommu/intel: synchronize page table map and unmap operations

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20231221031915.619337-3-pasha.tatashin@soleen.com>
Date: Thu, 21 Dec 2023 03:19:14 +0000
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: akpm@...ux-foundation.org,
	linux-mm@...ck.org,
	pasha.tatashin@...een.com,
	linux-kernel@...r.kernel.org,
	rientjes@...gle.com,
	dwmw2@...radead.org,
	baolu.lu@...ux.intel.com,
	joro@...tes.org,
	will@...nel.org,
	robin.murphy@....com,
	iommu@...ts.linux.dev
Subject: [RFC 2/3] iommu/intel: synchronize page table map and unmap operations

Since, we are going to update  parent page table entries when lower
level page tables become emtpy and we add them to the free list.
We need a way to synchronize the operation.

Use domain->pgd_lock to protect all map and unmap operations.
This is reader/writer lock. At the beginning everything is going to be
read only mode, however, later, when free page table on unmap is added
we will add a writer section as well.

Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
---
 drivers/iommu/intel/iommu.c | 21 +++++++++++++++++++--
 drivers/iommu/intel/iommu.h |  3 +++
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 4688ef797161..733f25b277a3 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1082,11 +1082,13 @@ static void dma_pte_free_pagetable(struct dmar_domain *domain,
 				   unsigned long last_pfn,
 				   int retain_level)
 {
+	read_lock(&domain->pgd_lock);
 	dma_pte_clear_range(domain, start_pfn, last_pfn);
 
 	/* We don't need lock here; nobody else touches the iova range */
 	dma_pte_free_level(domain, agaw_to_level(domain->agaw), retain_level,
 			   domain->pgd, 0, start_pfn, last_pfn);
+	read_unlock(&domain->pgd_lock);
 
 	/* free pgd */
 	if (start_pfn == 0 && last_pfn == DOMAIN_MAX_PFN(domain->gaw)) {
@@ -1179,9 +1181,11 @@ static void domain_unmap(struct dmar_domain *domain, unsigned long start_pfn,
 	    WARN_ON(start_pfn > last_pfn))
 		return;
 
+	read_lock(&domain->pgd_lock);
 	/* we don't need lock here; nobody else touches the iova range */
 	dma_pte_clear_level(domain, agaw_to_level(domain->agaw),
 			    domain->pgd, 0, start_pfn, last_pfn, freelist);
+	read_unlock(&domain->pgd_lock);
 
 	/* free pgd */
 	if (start_pfn == 0 && last_pfn == DOMAIN_MAX_PFN(domain->gaw)) {
@@ -2217,6 +2221,7 @@ __domain_mapping(struct dmar_domain *domain, unsigned long iov_pfn,
 
 	pteval = ((phys_addr_t)phys_pfn << VTD_PAGE_SHIFT) | attr;
 
+	read_lock(&domain->pgd_lock);
 	while (nr_pages > 0) {
 		uint64_t tmp;
 
@@ -2226,8 +2231,10 @@ __domain_mapping(struct dmar_domain *domain, unsigned long iov_pfn,
 
 			pte = pfn_to_dma_pte(domain, iov_pfn, &largepage_lvl,
 					     gfp);
-			if (!pte)
+			if (!pte) {
+				read_unlock(&domain->pgd_lock);
 				return -ENOMEM;
+			}
 			first_pte = pte;
 
 			lvl_pages = lvl_to_nr_pages(largepage_lvl);
@@ -2287,6 +2294,7 @@ __domain_mapping(struct dmar_domain *domain, unsigned long iov_pfn,
 			pte = NULL;
 		}
 	}
+	read_unlock(&domain->pgd_lock);
 
 	return 0;
 }
@@ -4013,6 +4021,7 @@ static int md_domain_init(struct dmar_domain *domain, int guest_width)
 	domain->pgd = alloc_pgtable_page(domain->nid, GFP_ATOMIC);
 	if (!domain->pgd)
 		return -ENOMEM;
+	rwlock_init(&domain->pgd_lock);
 	domain_flush_cache(domain, domain->pgd, PAGE_SIZE);
 	return 0;
 }
@@ -4247,11 +4256,15 @@ static size_t intel_iommu_unmap(struct iommu_domain *domain,
 	unsigned long start_pfn, last_pfn;
 	int level = 0;
 
+	read_lock(&dmar_domain->pgd_lock);
 	/* Cope with horrid API which requires us to unmap more than the
 	   size argument if it happens to be a large-page mapping. */
 	if (unlikely(!pfn_to_dma_pte(dmar_domain, iova >> VTD_PAGE_SHIFT,
-				     &level, GFP_ATOMIC)))
+				     &level, GFP_ATOMIC))) {
+		read_unlock(&dmar_domain->pgd_lock);
 		return 0;
+	}
+	read_unlock(&dmar_domain->pgd_lock);
 
 	if (size < VTD_PAGE_SIZE << level_to_offset_bits(level))
 		size = VTD_PAGE_SIZE << level_to_offset_bits(level);
@@ -4315,8 +4328,10 @@ static phys_addr_t intel_iommu_iova_to_phys(struct iommu_domain *domain,
 	int level = 0;
 	u64 phys = 0;
 
+	read_lock(&dmar_domain->pgd_lock);
 	pte = pfn_to_dma_pte(dmar_domain, iova >> VTD_PAGE_SHIFT, &level,
 			     GFP_ATOMIC);
+	read_unlock(&dmar_domain->pgd_lock);
 	if (pte && dma_pte_present(pte))
 		phys = dma_pte_addr(pte) +
 			(iova & (BIT_MASK(level_to_offset_bits(level) +
@@ -4919,8 +4934,10 @@ static int intel_iommu_read_and_clear_dirty(struct iommu_domain *domain,
 		struct dma_pte *pte;
 		int lvl = 0;
 
+		read_lock(&dmar_domain->pgd_lock);
 		pte = pfn_to_dma_pte(dmar_domain, iova >> VTD_PAGE_SHIFT, &lvl,
 				     GFP_ATOMIC);
+		read_unlock(&dmar_domain->pgd_lock);
 		pgsize = level_size(lvl) << VTD_PAGE_SHIFT;
 		if (!pte || !dma_pte_present(pte)) {
 			iova += pgsize;
diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
index f1ea508f45bd..cb0577ec5166 100644
--- a/drivers/iommu/intel/iommu.h
+++ b/drivers/iommu/intel/iommu.h
@@ -618,6 +618,9 @@ struct dmar_domain {
 		struct {
 			/* virtual address */
 			struct dma_pte	*pgd;
+
+			/* Synchronizes pgd map/unmap operations */
+			rwlock_t	pgd_lock;
 			/* max guest address width */
 			int		gaw;
 			/*
-- 
2.43.0.472.g3155946c3a-goog