Re: [PATCH v2 5/8] iommu/vt-d: Add first level page table interfaces

Lu Baolu
2019-12-03T02:37:28Z

Hi,

On 12/3/19 7:27 AM, Jacob Pan wrote:
> On Thu, 28 Nov 2019 10:25:47 +0800
> Lu Baolu<baolu.lu@linux.intel.com> wrote:
>
>> This adds functions to manipulate first level page tables
>> which could be used by a scalale mode capable IOMMU unit.
>>
> FL and SL page tables are very similar, and I presume we are not using
> all the flag bits in FL paging structures for DMA mapping. Are there
> enough relevant differences to warrant a new set of helper functions
> for FL? Or we can merge into one.
>

I ever thought about this and I am still open for this suggestion.

We had a quick compare on these two page tables. The only concern is the
read/write/present encoding. The present bit in first level implies read
permission while second level page table explicitly has a READ bit.
(recalled from memory, correct me if it's bad. :-)).

Anyway, let's listen to more opinions.

Best regards,
baolu