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Date: Fri, 12 Sep 2014 14:45:15 -0600 From: Toshi Kani <toshi.kani@...com> To: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com> Cc: hpa@...or.com, tglx@...utronix.de, mingo@...hat.com, akpm@...ux-foundation.org, arnd@...db.de, linux-mm@...ck.org, linux-kernel@...r.kernel.org, jgross@...e.com, stefan.bader@...onical.com, luto@...capital.net, hmh@....eng.br, yigal@...xistor.com Subject: Re: [PATCH v2 1/6] x86, mm, pat: Set WT to PA4 slot of PAT MSR On Fri, 2014-09-12 at 15:33 -0400, Konrad Rzeszutek Wilk wrote: > > - /* Set PWT to Write-Combining. All other bits stay the same */ > > - /* > > - * PTE encoding used in Linux: > > - * PAT > > - * |PCD > > - * ||PWT > > - * ||| > > - * 000 WB _PAGE_CACHE_WB > > - * 001 WC _PAGE_CACHE_WC > > - * 010 UC- _PAGE_CACHE_UC_MINUS > > - * 011 UC _PAGE_CACHE_UC > > > I think having this nice picture would be beneficial to folks > who want to understand it. And now you can of course expand it with > the slot 7 usage. OK, I will try to preserve the picture. > > - * PAT bit unused > > - */ > > - pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) | > > - PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC); > > + if ((c->x86_vendor == X86_VENDOR_INTEL) && > > + (((c->x86 == 0x6) && (c->x86_model <= 0xd)) || > > + ((c->x86 == 0xf) && (c->x86_model <= 0x6)))) { > > + /* > > + * Intel Pentium 2, 3, M, and 4 are affected by PAT errata, > > + * which makes the upper four entries unusable. We do not > > + * use the upper four entries for all the affected processor > > + * families for safe. > > + * > > + * PAT 0:WB, 1:WC, 2:UC-, 3:UC, 4-7:unusable > > + * > > + * NOTE: When WT or WP is used, it is redirected to UC- per > > + * the default setup in __cachemode2pte_tbl[]. > > + */ > > + pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) | > > + PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC); > > + } else { > > + /* > > + * WT is set to slot 7, which minimizes the risk of using > > You say slot 7 here, but the title of the patch says slot 4? Oops! I will fix the title. Thanks for reviewing! -Toshi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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