RE: [PATCH v3 5/5] intel_iommu: Optimize out some unnecessary UNMAP calls

[Duan, Zhenzhong]

>-----Original Message-----
>From: Peter Xu <peterx@redhat.com>
>Sent: Saturday, June 10, 2023 5:26 AM
>Subject: Re: [PATCH v3 5/5] intel_iommu: Optimize out some unnecessary
>UNMAP calls
>
>On Fri, Jun 09, 2023 at 05:49:06AM +0000, Duan, Zhenzhong wrote:
>> Seems vtd_page_walk_one() already works in above way, checking mapping
>> changes and calling kernel for changed entries?
>
>Agreed in most cases, but the path this patch modified is not?  E.g. it happens
>in rare cases where we simply want to unmap everything (e.g. on a system
>reset, or invalid context entry)?
Clear.

>
>That's also why I'm curious whether perf of this path matters at all (and
>assuming now we all agree that's the only goal now..), because afaiu it didn't
>really trigger in common paths.
I'll collect performance data and reply back.

Thanks
Zhenzhong