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Message-ID: <1405963247.31023.0.camel@misato.fc.hp.com> Date: Mon, 21 Jul 2014 11:20:47 -0600 From: Toshi Kani <toshi.kani@...com> To: "H. Peter Anvin" <hpa@...or.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, tglx@...utronix.de, mingo@...hat.com, akpm@...ux-foundation.org, arnd@...db.de, plagnioj@...osoft.com, tomi.valkeinen@...com, linux-mm@...ck.org, linux-kernel@...r.kernel.org, stefan.bader@...onical.com, luto@...capital.net, airlied@...il.com, bp@...en8.de Subject: Re: [RFC PATCH 0/11] Support Write-Through mapping on x86 On Mon, 2014-07-21 at 09:47 -0700, H. Peter Anvin wrote: > On 07/21/2014 09:31 AM, Toshi Kani wrote: > > Do you have any comments / suggestions for this approach? > > Approach to what, specifically? > > Keep in mind the PAT bit is different for large pages. This needs to be > dealt with. You are right. I was under a wrong impression that __change_page_attr() always splits a large pages into 4KB pages, but I overlooked the fact that it can handle a large page as well. So, this approach does not work... > I would also like a systematic way to deal with the fact > that Xen (sigh) is stuck with a separate mapping system. > > I guess Linux could adopt the Xen mappings if that makes it easier, as > long as that doesn't have a negative impact on native hardware -- we can > possibly deal with some older chips not being optimal. I see. I agree that supporting the PAT bit is the right direction, but I do not know how much effort we need. I will study on this. > However, my thinking has been to have a "reverse PAT" table in memory of memory > types to encodings, both for regular and large pages. I am not clear about your idea of the "reverse PAT" table. Would you care to elaborate? How is it different from using pte_val() being a paravirt function on Xen? Thanks, -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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