Messages in this thread | | | Date | Mon, 17 Jun 2013 11:38:37 +0800 | From | "Li, Zhen-Hua (USL-China)" <> | Subject | Re: [PATCH 1/1] x86/iommu: fix dma pte address size error |
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Hi Don,
This patch is not only for the sake of spec interpretation. Till now I did not see any bugs , but it does not meant no bugs will appear in the future. The address returned by dma_pte_addr is used in many places.
Thanks Zhenhua
On 06/15/2013 04:16 AM, Don Dutile wrote: > 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@hp.com> >> --- >> 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 ? > > Cheers, > - 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; >> #else >> /* 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; >> #endif >> } >> >> 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) >> >> #define CONTEXT_TT_MULTI_LEVEL 0 >> #define CONTEXT_TT_DEV_IOTLB 1 > > . >
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