On Mon, 2015-07-20 at 08:46 +0100, Jan Beulich wrote:
> Make WT really mean WT (rather than UC).
>
> I can't see why commit 9cd25aac1f ("x86/mm/pat: Emulate PAT when it is
> disabled") didn't make this match its changes to pat_init().
No, the default values need to be set to the fallback types, i.e. minimal
supported mode. For WC and WT, UC is the fallback type.
When PAT is disabled, pat_init() does update the tables below to enable WT
per the default BIOS setup. However, when PAT is enabled, but CPU has PAT
-errata, WT falls back to UC per the default values.
Thanks,
-Toshi
>
> Signed-off-by: Jan Beulich <jbeul...@suse.com>
> Cc: Borislav Petkov <b...@suse.de>
> Cc: Toshi Kani <toshi.k...@hp.com>
> ---
> arch/x86/mm/init.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> --- 4.2-rc3/arch/x86/mm/init.c
> +++ 4.2-rc3-x86-default-cache-mode/arch/x86/mm/init.c
> @@ -43,18 +43,18 @@ uint16_t __cachemode2pte_tbl[_PAGE_CACHE
> [_PAGE_CACHE_MODE_WC ] = 0 | _PAGE_PCD,
> [_PAGE_CACHE_MODE_UC_MINUS] = 0 | _PAGE_PCD,
> [_PAGE_CACHE_MODE_UC ] = _PAGE_PWT | _PAGE_PCD,
> - [_PAGE_CACHE_MODE_WT ] = 0 | _PAGE_PCD,
> + [_PAGE_CACHE_MODE_WT ] = _PAGE_PWT | 0,
> [_PAGE_CACHE_MODE_WP ] = 0 | _PAGE_PCD,
> };
> EXPORT_SYMBOL(__cachemode2pte_tbl);
>
> uint8_t __pte2cachemode_tbl[8] = {
> [__pte2cm_idx( 0 | 0 | 0 )] =
> _PAGE_CACHE_MODE_WB,
> - [__pte2cm_idx(_PAGE_PWT | 0 | 0 )] =
> _PAGE_CACHE_MODE_UC_MINUS,
> + [__pte2cm_idx(_PAGE_PWT | 0 | 0 )] =
> _PAGE_CACHE_MODE_WT,
> [__pte2cm_idx( 0 | _PAGE_PCD | 0 )] =
> _PAGE_CACHE_MODE_UC_MINUS,
> [__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | 0 )] =
> _PAGE_CACHE_MODE_UC,
> [__pte2cm_idx( 0 | 0 | _PAGE_PAT)] =
> _PAGE_CACHE_MODE_WB,
> - [__pte2cm_idx(_PAGE_PWT | 0 | _PAGE_PAT)] =
> _PAGE_CACHE_MODE_UC_MINUS,
> + [__pte2cm_idx(_PAGE_PWT | 0 | _PAGE_PAT)] =
> _PAGE_CACHE_MODE_WT,
> [__pte2cm_idx(0 | _PAGE_PCD | _PAGE_PAT)] =
> _PAGE_CACHE_MODE_UC_MINUS,
> [__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | _PAGE_PAT)] =
> _PAGE_CACHE_MODE_UC,
> };
>
>
>
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