Re: [PATCH] Fix bug in iommu_context_addr: Always get pointer to lower extended-context-table

From: joro@xxxxxxxxxx
Date: Tue Aug 25 2015 - 04:42:20 EST


Hi Nan,

On Mon, Aug 24, 2015 at 06:26:33AM +0000, Xiao, Nan (Nan@HPS Performance, Beijing) wrote:
> drivers/iommu/intel-iommu.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 0649b94..4213598 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -759,10 +759,11 @@ static inline struct context_entry *iommu_context_addr(struct intel_iommu *iommu
> if (devfn >= 0x80) {
> devfn -= 0x80;
> entry = &root->hi;
> - }
> + } else
> + entry = &root->lo;
> devfn *= 2;
> - }
> - entry = &root->lo;
> + } else
> + entry = &root->lo;
> if (*entry & 1)
> context = phys_to_virt(*entry & VTD_PAGE_MASK);
> else {

Shouldn't this diff have the same effect?

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 0649b94..7553cb9 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -755,6 +755,7 @@ static inline struct context_entry *iommu_context_addr(struct intel_iommu *iommu
struct context_entry *context;
u64 *entry;

+ entry = &root->lo;
if (ecs_enabled(iommu)) {
if (devfn >= 0x80) {
devfn -= 0x80;
@@ -762,7 +763,6 @@ static inline struct context_entry *iommu_context_addr(struct intel_iommu *iommu
}
devfn *= 2;
}
- entry = &root->lo;
if (*entry & 1)
context = phys_to_virt(*entry & VTD_PAGE_MASK);
else {
--
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