Messages in this thread | | | Date | Wed, 20 Aug 2014 13:21:22 +0100 | From | "Jan Beulich" <> | Subject | Re: [Xen-devel] [PATCH RFC 0/3] x86: Full support of PAT |
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>>> One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> 08/20/14 2:08 PM >>> >> The Linux kernel currently supports only 4 different cache modes. The PAT MSR >> is set up in a way that the setting of _PAGE_PAT in a pte doesn't matter: the >> top 4 entries in the PAT MSR are the same as the 4 lower entries. >> >> This results in the kernel not supporting e.g. write-through mode. Especially >> this cache mode would speed up drivers of video cards which now have to use >> uncached accesses. > >Pentium II erratum A52 (and similar on quite a few other processors)
But you're aware that for the last two major releases Xen hasn't been supporting 32-bit CPUs at all anymore? I.e. why should we limit functionality under Xen based on errata on 64-bit-incapable CPUs?
Jan
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