On Wed, 13 May 2015, Toshi Kani wrote: > This patch sets WT to the PA7 slot in the PAT MSR when the processor > is not affected by the PAT errata. The PA7 slot is chosen to improve > robustness in the presence of errata that might cause the high PAT bit > to be ignored. This way a buggy PA7 slot access will hit the PA3 slot, > which is UC, so at worst we lose performance without causing a correctness > issue. > > The following Intel processors are affected by the PAT errata. > > errata cpuid > ---------------------------------------------------- > Pentium 2, A52 family 0x6, model 0x5 > Pentium 3, E27 family 0x6, model 0x7, 0x8 > Pentium 3 Xenon, G26 family 0x6, model 0x7, 0x8, 0xa > Pentium M, Y26 family 0x6, model 0x9 > Pentium M 90nm, X9 family 0x6, model 0xd > Pentium 4, N46 family 0xf, model 0x0 > > Instead of making sharp boundary checks, this patch makes conservative > checks to exclude all Pentium 2, 3, M and 4 family processors. For > such processors, _PAGE_CACHE_MODE_WT is redirected to UC- per the > default setup in __cachemode2pte_tbl[]. > > Signed-off-by: Toshi Kani <toshi.kani@xxxxxx> > Reviewed-by: Juergen Gross <jgross@xxxxxxxx> Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>