>From 4b65fb80338c71673cabfa9fa9b0f80f5a4bc320 Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Tue, 16 Dec 2014 07:43:51 +0100 Subject: [PATCH] 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. Detect this bug and don't use the read value if it is 0. Commit bd809af16e3ab1f8d55b3e2928c47c67e2a865d2 ("x86: Enable PAT to use cache mode translation tables") triggers this VMWare bug when the kernel is booted as a VMWare guest. Reported-by: Jongman Heo Signed-off-by: Juergen Gross Tested-by: Jongman Heo --- arch/x86/mm/pat.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c index edf299c..7ac6869 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); -- 2.1.2