[RESUBMIT][PATCH] x86/mm: Fix PAT bit missing from page protection modify mask

[Juergen Gross]

On 02.06.23 16:43, Borislav Petkov wrote:
> On Thu, Jun 01, 2023 at 10:47:39AM +0200, Juergen Gross wrote:
>> As described in the commit message, this only works on bare metal due to the
>> PAT bit not being needed for WC mappings.
>>
>> Making this patch Xen specific would try to cure the symptoms without fixing
>> the underlying problem: _PAGE_PAT should be regarded the same way as the bits
>> for caching mode (_PAGE_CHG_MASK).
> 
> So why isn't _PAGE_PAT part of _PAGE_CHG_MASK?

This would result in problems for large pages: _PAGE_PSE is at the same
position as _PAGE_PAT (large pages are using _PAGE_PAT_LARGE instead).

Yes, x86 ABI is a mess.


Juergen

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