[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Re: [PATCH 06/16] xen: disable PAT
Keir Fraser wrote: > > My suggestion is that Xen changes its PAT[1] from WT to WC. AFAIK only > suse's Linux port is currently using Xen's PAT support, and it does not > actually use the WT cache attribute. Then Xen's PAT[0-3] would match what > Linux expects, and Linux apparently does not risk using PAT[4-7] because of > processor errata so their values are irrelevant. Linux can check that it is > running on Xen with suitable PAT setup by reading MSR_IA32_CR_PAT and > checking PAT[0-3], and only enable PAT usage in case of a match. > There exists at least one processor erratum where the CPU will use PAT[4-7] when the user requested PAT[0-3]. For those CPUs, it is unsafe for *any* OS to have PAT[4-7] != PAT[0-3]. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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