Re: [Xen-devel] [PATCH v2 3/4] amd-iommu: disable iommu_hap_pt_share with AMD IOMMUs

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.04.14 at 16:31, <roger.pau@xxxxxxxxxx> wrote:
> On 23/04/14 12:51, Jan Beulich wrote:
>>>>> On 23.04.14 at 12:04, <roger.pau@xxxxxxxxxx> wrote:
>>> On 23/04/14 11:57, Jan Beulich wrote:
>>>>>>> On 23.04.14 at 10:16, <roger.pau@xxxxxxxxxx> wrote:
>>>>> According to the comment in p2m.h, AMD IOMMUs don't work correctly
>>>>> with page types different than p2m_ram_rw when the p2m is shared
>>>>> between HAP and IOMMU, so disable this sharing when using AMD IOMMUs.
>>>>
>>>> Doesn't this need to go before patch 2?
>>>
>>> It could certainly go before patch 2, but I don't see such a hard
>>> requirement in the ordering (either way AMD hardware needs both patches
>>> to work correctly, and applying one before the other is not going to
>>> break bisection AFAICT).
>> 
>> Patch 2 allows the high bits in present IOMMU entries to be non-zero,
>> thus allowing for IOMMU faults without this patch already in effect.
> 
> Since on AMD hardware iommu_hap_pt_share is always true (unless the user
> forces it to false), the previous patch has no effect without this one
> (because the previous patch only deals with iommu_hap_pt_share ==
> false). I don't mind moving it anyway, and will do it in the next version.

And right you are - feel free to keep the order then as it was.

Jan


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