From: Juergen Gross Date: Mon, 12 Jan 2015 05:15:45 +0000 (+0100) Subject: x86: Don't rely on VMWare emulating PAT MSR correctly X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=9d34cfdf4796;p=deliverable%2Flinux.git x86: Don't rely on VMWare emulating PAT MSR correctly VMWare seems not to emulate the PAT MSR correctly: reaeding MSR_IA32_CR_PAT returns 0 even after writing another value to it. Commit bd809af16e3ab triggers this VMWare bug when the kernel is booted as a VMWare guest. Detect this bug and don't use the read value if it is 0. Fixes: bd809af16e3ab "x86: Enable PAT to use cache mode translation tables" Reported-and-tested-by: Jongman Heo Acked-by: Alok N Kataria Signed-off-by: Juergen Gross Link: http://lkml.kernel.org/r/1421039745-14335-1-git-send-email-jgross@suse.com Signed-off-by: Thomas Gleixner --- diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c index edf299c8ff6c..7ac68698406c 100644 --- a/arch/x86/mm/pat.c +++ b/arch/x86/mm/pat.c @@ -234,8 +234,13 @@ void pat_init(void) PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC); /* Boot CPU check */ - if (!boot_pat_state) + if (!boot_pat_state) { rdmsrl(MSR_IA32_CR_PAT, boot_pat_state); + if (!boot_pat_state) { + pat_disable("PAT read returns always zero, disabled."); + return; + } + } wrmsrl(MSR_IA32_CR_PAT, pat);