On 06/23/2013 12:29 PM, Henrique de Moraes Holschuh wrote: > On Sun, 23 Jun 2013, H. Peter Anvin wrote: >> Why do you care about performance when PAT is disabled? > > It will regress already slow boxes. We blacklist a LOT of P4s, PMs, etc and > nobody ever took the pain to track down which ones of those actually have > PAT+MTRR aliasing bugs. > > These boxes have boards like the Radeon X300, which needs either PAT or MTRR > to not become unusable... > We're talking hardware which is now many years old, but this is causing very serious problems on real, modern hardware. As far as I understand it, too, the blacklisting was precautionary (the only bug that I personally know about is a performance bug, where WC would be incorrectly converted to UC.) We need a way forward here. If it is the only way I think we would have to sacrifice the old machines, but perhaps something can be worked out (e.g. if PAT is disabled, fall back to MTRRs if available for ioremap_wc()). -hpa _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
