Messages in this thread | | | Date | Wed, 10 Sep 2014 12:14:30 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH v2 2/6] x86, mm, pat: Change reserve_memtype() to handle WT |
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On 09/10/2014 11:26 AM, Andy Lutomirski wrote: > On Wed, Sep 10, 2014 at 9:51 AM, Toshi Kani <toshi.kani@hp.com> wrote: >> This patch changes reserve_memtype() to handle the WT cache mode. >> When PAT is not enabled, it continues to set UC- to *new_type for >> any non-WB request. >> >> When a target range is RAM, reserve_ram_pages_type() fails for WT >> for now. This function may not reserve a RAM range for WT since >> reserve_ram_pages_type() uses the page flags limited to three memory >> types, WB, WC and UC. > > Should it fail if WT is unavailable due to errata? More generally, > how are all of the do_something_wc / do_something_wt / > do_something_nocache helpers supposed to handle unsupported types? >
Errata, or because it is pre-PAT hardware. Keep in mind that even pre-PAT hardware supports using page tables for cache types, it is only that the only types supposed are WB, WT, UC.
-hpa
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