Re: [PATCH 1/1] x86/iommu: fix dma pte address size error

From: Don Dutile
Date: Fri Jun 14 2013 - 16:17:14 EST

On 05/23/2013 08:35 PM, Li, Zhen-Hua wrote:
In Intel Vt-D specs, Chapter 9.3 Page-Table Entry,
The size of ADDR(address) field is 12:51, but the function dma_pte_addr
treats it as 12:63.

Signed-off-by: Li, Zhen-Hua<zhen-hual@xxxxxx>
drivers/iommu/intel-iommu.c | 4 ++--
include/linux/dma_remapping.h | 2 ++
2 files changed, 4 insertions(+), 2 deletions(-)

Is this patching for the sake of spec interpretation?
a dma-pte format (consumed by iommu) has 63,61:52 as available for sw, ignored by hw.
62 is 'transient mapping' bit, which is a _hint_ for selecting iotlbs to flush sooner.
finally, the system would have to have a memory map that actually has bit 62 set to
be affected.

So, for intel-iommu, I don't see a bug occurring.
Did you actually have one with previous definition, and if so,
could you provide that information ?

- Don
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index b4f0e28..c6d2847 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -311,10 +311,10 @@ static inline void dma_set_pte_prot(struct dma_pte *pte, unsigned long prot)
static inline u64 dma_pte_addr(struct dma_pte *pte)
#ifdef CONFIG_64BIT
- return pte->val& VTD_PAGE_MASK;
+ return pte->val& DMA_PTE_MASK;
/* Must have a full atomic 64-bit read */
- return __cmpxchg64(&pte->val, 0ULL, 0ULL)& VTD_PAGE_MASK;
+ return __cmpxchg64(&pte->val, 0ULL, 0ULL)& DMA_PTE_MASK;

diff --git a/include/linux/dma_remapping.h b/include/linux/dma_remapping.h
index 57c9a8a..7a1e212 100644
--- a/include/linux/dma_remapping.h
+++ b/include/linux/dma_remapping.h
@@ -16,6 +16,8 @@
#define DMA_PTE_WRITE (2)
#define DMA_PTE_LARGE_PAGE (1<< 7)
#define DMA_PTE_SNP (1<< 11)
+#define DMA_PTE_ADD_LENGTH (40)
+#define DMA_PTE_MASK ((((u64)1<< DMA_PTE_ADD_LENGTH) - 1)<< VTD_PAGE_SHIFT)


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