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SubjectRe: [PATCH v5 3/3] x86/tdx: Add Quote generation support

On 5/3/22 3:28 PM, Sathyanarayanan Kuppuswamy wrote:
> On 5/3/22 3:24 PM, Dave Hansen wrote:
>> On 5/2/22 18:27, Kirill A. Shutemov wrote:
>>>> Again, Dave and Andi already commented you should use vmap() to
>>>> avoid breaking
>>>> up the direct-mapping.  Please use vmap() instead.
>>>> Will review the rest later.
>>> I would rather convert it to use DMA API for memory allocation. It will
>>> tap into swiotlb buffer that already converted and there's no need to
>>> touch direct mapping. Both allocation and freeing such memory is cheaper
>>> because of that.
>> Sathya, I don't quite understand why you are so forcefully declining to
>> incorporate review feedback on this point.  I gave very specific
>> feedback about the kind of mapping you need and that you should avoid
>> fragmenting the direct map if at all possible.
>> Why is this code still fragmenting the direct map?
> I have already implemented it and testing it now.

I mean, I have already implemented the vmap based solution.

> In this discussion, we are comparing the use of DMA API for memory
> allocation vs vmap/sharing it in driver itself.

Sathyanarayanan Kuppuswamy
Linux Kernel Developer

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