Re: [PATCH v2 0/2] iommu/amd: Don't use atomic64_t for domain->pt_root

Joerg Roedel
2020-06-30T09:57:26Z

On Fri, Jun 26, 2020 at 08:30:21AM -0400, Qian Cai wrote:
> BTW, from the previous discussion, Linus mentioned,
>
> “
> The thing is, the 64-bit atomic reads/writes are very expensive on
> 32-bit x86. If it was just a native pointer, it would be much cheaper
> than an "atomic64_t".
> “
>
> However, here we have AMD_IOMMU depend on x86_64, so I am wondering if
> it makes any sense to run this code on 32-bit x86 at all?

No, it doesn't, the driver is not supported on 32bit and probably never
will. I skip this patch and only apply the first one, as it is an
improvement in itself.

Regards,

Joerg