linux-kernel - Re: [PATCH v6 14/41] x86/mm: Introduce _PAGE_SAVED

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Message-ID: <982781d9cde9173a95939b0216351ec9d97014bb.camel@intel.com>
Date:   Tue, 21 Feb 2023 20:08:24 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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CC:     "Yu, Yu-cheng" <yu-cheng.yu@...el.com>
Subject: Re: [PATCH v6 14/41] x86/mm: Introduce _PAGE_SAVED_DIRTY

On Tue, 2023-02-21 at 09:38 +0100, David Hildenbrand wrote:
> Again, I'd not specialize on COW in all patches to much (IMHO, it 
> creates more confusion than it actually helps for understanding
> what's 
> happening) and just call it a read-only PTE that is dirty. Simple as 
> that. And it's easy to see why that's problematic, because read-only 
> PTEs that are dirty would be identified as shadow stack PTEs, which
> we 
> want to work around.
> 
> Again, just my 2 cents. I'm not an x86 maintainer ;)

Right, I see the point. Let's see if they have any opinion. There is a
bit of a historical reason for the focus on COW. As you well know the
dirty bit used to be important for that case. But I think it's still
not a terrible example. It covers some typical cases, but yes we don't
want to mislead the reader that it is a Cow only scenario.