On 02.06.23 16:48, Juergen Gross wrote:
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.
Oh, wait: I originally thought _PAGE_CHG_MASK would be used for large pages, too. There is _HPAGE_CHG_MASK for that purpose. So adding _PAGE_PAT to _PAGE_CHG_MASK and _PAGE_PAT_LARGE to _HPAGE_CHG_MASK should do the job. At least I hope so. Juergen
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