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FAILED: patch "[PATCH] iommu/vt-d: Force to flush iotlb before creating superpage" failed to apply to 5.4-stable tree

PATCH [email protected] 1 participant 1 message May 9, 2021

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The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 38c527aeb41926c71902dd42f788a8b093b21416 Mon Sep 17 00:00:00 2001
From: "Longpeng(Mike)" <[email protected]>
Date: Thu, 15 Apr 2021 08:46:28 +0800
Subject: [PATCH] iommu/vt-d: Force to flush iotlb before creating superpage

The translation caches may preserve obsolete data when the mapping size is changed, suppose the following sequence which can reveal the problem with high probability.

1.mmap(4GB,MAP_HUGETLB)
2.
while (1) {

   (a)    DMA MAP   0,0xa0000
   (b)    DMA UNMAP 0,0xa0000
   (c)    DMA MAP   0,0xc0000000

* DMA read IOVA 0 may failure here (Not present)
* if the problem occurs.
(d) DMA UNMAP 0,0xc0000000
}

The page table(only focus on IOVA 0) after (a) is:

 PML4: 0x19db5c1003   entry:0xffff899bdcd2f000
  PDPE: 0x1a1cacb003  entry:0xffff89b35b5c1000
   PDE: 0x1a30a72003  entry:0xffff89b39cacb000
    PTE: 0x21d200803  entry:0xffff89b3b0a72000

The page table after (b) is:

 PML4: 0x19db5c1003   entry:0xffff899bdcd2f000
  PDPE: 0x1a1cacb003  entry:0xffff89b35b5c1000
   PDE: 0x1a30a72003  entry:0xffff89b39cacb000
    PTE: 0x0          entry:0xffff89b3b0a72000

The page table after (c) is:

 PML4: 0x19db5c1003   entry:0xffff899bdcd2f000
  PDPE: 0x1a1cacb003  entry:0xffff89b35b5c1000
   PDE: 0x21d200883   entry:0xffff89b39cacb000 (*)

Because the PDE entry after (b) is present, it won't be flushed even if the iommu driver flush cache when unmap, so the obsolete data may be preserved in cache, which would cause the wrong translation at end.

However, we can see the PDE entry is finally switch to 2M-superpage mapping, but it does not transform to 0x21d200883 directly:

1. PDE: 0x1a30a72003
2. __domain_mapping
dma_pte_free_pagetable
Set the PDE entry to ZERO
Set the PDE entry to 0x21d200883

So we must flush the cache after the entry switch to ZERO to avoid the obsolete info be preserved.

Cc David Woodhouse <[email protected]>
Cc Lu Baolu <[email protected]>
Cc Nadav Amit <[email protected]>
Cc Alex Williamson <[email protected]>
Cc Joerg Roedel <[email protected]>
Cc Kevin Tian <[email protected]>
Cc Gonglei (Arei) <[email protected]>
Fixes 6491d4d02893 ("intel-iommu: Free old page tables before creating superpage")
Cc <[email protected]> # v3.0+
Link https://lore.kernel.org/linux-iommu/[email protected]/ open here
Suggested-by Lu Baolu <[email protected]>
Signed-off-by Longpeng(Mike) <[email protected]>
Acked-by Lu Baolu <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
Signed-off-by Joerg Roedel <[email protected]>
drivers/iommu/intel/iommu.c +38 -14
index c981e69bc107..ab2a026dd844 100644
@@ -2301,6 +2301,41 @@ static inline int hardware_largepage_caps(struct dmar_domain *domain,
 	return level;
 }
 
+/*
+ * Ensure that old small page tables are removed to make room for superpage(s).
+ * We're going to add new large pages, so make sure we don't remove their parent
+ * tables. The IOTLB/devTLBs should be flushed if any PDE/PTEs are cleared.
+ */
+static void switch_to_super_page(struct dmar_domain *domain,
+				 unsigned long start_pfn,
+				 unsigned long end_pfn, int level)
+{
+	unsigned long lvl_pages = lvl_to_nr_pages(level);
+	struct dma_pte *pte = NULL;
+	int i;
+
+	while (start_pfn <= end_pfn) {
+		if (!pte)
+			pte = pfn_to_dma_pte(domain, start_pfn, &level);
+
+		if (dma_pte_present(pte)) {
+			dma_pte_free_pagetable(domain, start_pfn,
+					       start_pfn + lvl_pages - 1,
+					       level + 1);
+
+			for_each_domain_iommu(i, domain)
+				iommu_flush_iotlb_psi(g_iommus[i], domain,
+						      start_pfn, lvl_pages,
+						      0, 0);
+		}
+
+		pte++;
+		start_pfn += lvl_pages;
+		if (first_pte_in_page(pte))
+			pte = NULL;
+	}
+}
+
 static int
 __domain_mapping(struct dmar_domain *domain, unsigned long iov_pfn,
 		 unsigned long phys_pfn, unsigned long nr_pages, int prot)

@@ -2342,22 +2377,11 @@ __domain_mapping(struct dmar_domain *domain, unsigned long iov_pfn,
 				return -ENOMEM;
 			/* It is large page*/
 			if (largepage_lvl > 1) {
-				unsigned long nr_superpages, end_pfn;
+				unsigned long end_pfn;
 
 				pteval |= DMA_PTE_LARGE_PAGE;
-				lvl_pages = lvl_to_nr_pages(largepage_lvl);
-
-				nr_superpages = nr_pages / lvl_pages;
-				end_pfn = iov_pfn + nr_superpages * lvl_pages - 1;
-
-				/*
-				 * Ensure that old small page tables are
-				 * removed to make room for superpage(s).
-				 * We're adding new large pages, so make sure
-				 * we don't remove their parent tables.
-				 */
-				dma_pte_free_pagetable(domain, iov_pfn, end_pfn,
-						       largepage_lvl + 1);
+				end_pfn = ((iov_pfn + nr_pages) & level_mask(largepage_lvl)) - 1;
+				switch_to_super_page(domain, iov_pfn, end_pfn, largepage_lvl);
 			} else {
 				pteval &= ~(uint64_t)DMA_PTE_LARGE_PAGE;
 			}