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

From: Xunlei Pang
Date: Mon Oct 10 2016 - 09:01:25 EST


Ping David for confirmation

On 2016/09/19 at 20:18, Joerg Roedel wrote:
> [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
>