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SubjectRe: [PATCH v6] swiotlb: Adjust SWIOTBL bounce buffer size for SEV guests.
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> On Nov 24, 2020, at 3:38 AM, Borislav Petkov <bp@alien8.de> wrote:
>
> On Tue, Nov 24, 2020 at 09:25:06AM +0000, Kalra, Ashish wrote:
>> But what will be the criteria to figure out this percentage?
>>
>> As I mentioned earlier, this can be made as complicated as possible by
>> adding all kind of heuristics but without any predictable performance
>> gain.
>>
>> Or it can be kept simple by using a static percentage value.
>
> Yes, static percentage number based on the guest memory. X% of the guest
> memory is used for SWIOTLB.
>
> Since you use sev_active(), it means the size computation is done in the
> guest so that SWIOTLB size is per-guest. Yes?

Yes

>
> If so, you can simply take, say, 5% of the guest memory's size and use
> that for SWIOTLB buffers. Or 6 or X or whatever.
>
> Makes sense?

Sure it does.

Thanks,
Ashish

>
> --
> Regards/Gruss,
> Boris.
>
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