>-----Original Message-----
>From: Nicolin Chen <[email protected]>
>Subject: Re: [PATCH v7 09/23] intel_iommu: Stick to system MR for
>IOMMUFD backed host device when x-flts=on
>
>On Fri, Oct 31, 2025 at 09:52:16AM +0000, Duan, Zhenzhong wrote:
>> >> + /*
>> >> + * When guest enables scalable mode and sets up first stage page
>> >table,
>> >> + * we stick to system MR for IOMMUFD backed host device. Then
>its
>> >> + * default hwpt contains GPA->HPA mappings which is used
>directly if
>> >> + * PGTT=PT and used as nesting parent if PGTT=FST. Otherwise fall
>> >back
>> >> + * to original processing.
>> >According to the above comment you have a S1 translation in place but
>> >you set use_iommu = false and use system MR?
>>
>> Yes, we have extended the usages of MRs under IOMMU AS with nesting.
>> In nesting mode, system MR on/off isn't aligned with S1 translation
>anymore.
>
>Does Intel vIOMMU need S1 translation when the working in the HW
>accelerated mode? I thought everything is handled by the HW..no?
It needs S1 translation for emulated device. For passthrough device, yes.
