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SubjectRe: [PATCH 1/2] x86/pat: fix x86_has_pat_wp()
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On 03.05.22 15:22, Juergen Gross wrote:
> x86_has_pat_wp() is using a wrong test, as it relies on the normal
> PAT configuration used by the kernel. In case the PAT MSR has been
> setup by another entity (e.g. BIOS or Xen hypervisor) it might return
> false even if the PAT configuration is allowing WP mappings.
>
> Fixes: 1f6f655e01ad ("x86/mm: Add a x86_has_pat_wp() helper")
> Signed-off-by: Juergen Gross <jgross@suse.com>
> ---
> arch/x86/mm/init.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> index d8cfce221275..71e182ebced3 100644
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -80,7 +80,8 @@ static uint8_t __pte2cachemode_tbl[8] = {
> /* Check that the write-protect PAT entry is set for write-protect */
> bool x86_has_pat_wp(void)
> {
> - return __pte2cachemode_tbl[_PAGE_CACHE_MODE_WP] == _PAGE_CACHE_MODE_WP;
> + return __pte2cachemode_tbl[__cachemode2pte_tbl[_PAGE_CACHE_MODE_WP]] ==
> + _PAGE_CACHE_MODE_WP;
> }
>
> enum page_cache_mode pgprot2cachemode(pgprot_t pgprot)

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