Re: [PATCH] iommu/vt-d: Fix the size calculation of pasid table

[Joerg Roedel]

[Cc'ing David]

On Mon, Sep 12, 2016 at 10:49:11AM +0800, Xunlei Pang wrote:
> According to the vt-d spec, the size of pasid (state) entry is 8B
> which equals 3 in power of 2, the number of pasid (state) entries
> is (ecap_pss + 1) in power of 2.
> 
> Thus the right size of pasid (state) table in power of 2 should be
> ecap_pss(iommu->ecap) plus "1+3=4" other than 7.
> 
> Signed-off-by: Xunlei Pang <xlpang@xxxxxxxxxx>
> ---
>  drivers/iommu/intel-svm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
> index 8ebb353..cfa75c2 100644
> --- a/drivers/iommu/intel-svm.c
> +++ b/drivers/iommu/intel-svm.c
> @@ -39,7 +39,7 @@ int intel_svm_alloc_pasid_tables(struct intel_iommu *iommu)
>  	struct page *pages;
>  	int order;
>  
> -	order = ecap_pss(iommu->ecap) + 7 - PAGE_SHIFT;
> +	order = ecap_pss(iommu->ecap) + 4 - PAGE_SHIFT;
>  	if (order < 0)
>  		order = 0;

The patch seems to be correct, but I'll let David comment on it first.



	Joerg