linux-kernel - Re: [PATCH 0/4] arch, mm: improve robustness of direct map manipulation

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Message-ID: <b519c0cec8ad8e67d7a43251e45e49d17d5cfbef.camel@intel.com>
Date:   Thu, 29 Oct 2020 23:19:45 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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Subject: Re: [PATCH 0/4] arch, mm: improve robustness of direct map
 manipulation

On Thu, 2020-10-29 at 10:12 +0200, Mike Rapoport wrote:
> This series goal was primarily to separate dependincies and make it
> clearer what DEBUG_PAGEALLOC and what SET_DIRECT_MAP are. As it
> turned
> out, there is also some lack of consistency between architectures
> that
> implement either of this so I tried to improve this as well.
> 
> Honestly, I don't know if a thread can be paused at the time
> __vunmap()
> left invalid pages, but it could, there is an issue on arm64 with
> DEBUG_PAGEALLOC=n and this set fixes it.

Ah, ok. So from this and the other thread, this is about the logic in
arm's cpa for when it will try the un/map operations. I think the logic
actually works currently. And this series introduces a problem on ARM
similar to the one you are saying preexists. I put the details in the
other thread.