On Wed, Sep 10, 2014 at 1:30 PM, Toshi Kani <[email protected]> wrote: > On Wed, 2014-09-10 at 13:14 -0700, H. Peter Anvin wrote: >> On 09/10/2014 12:30 PM, Toshi Kani wrote: >> > >> > When WT is unavailable due to the PAT errata, it does not fail but gets >> > redirected to UC-. Similarly, when PAT is disabled, WT gets redirected >> > to UC- as well. >> > >> >> But on pre-PAT hardware you can still do WT. > > Yes, if we manipulates the bits directly, but such code is no longer > allowed for PAT systems. The PAT-based kernel interfaces won't work for > pre-PAT systems, and therefore requests are redirected to UC- on such > systems. >
Right, the PWT bit. Forgot about that. I wonder whether it would make sense to do some followup patches to replace the current support for non-PAT machines with a "PAT" and corresponding reverse map that exactly matches the mapping when PAT is disabled. These patches are almost there. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
