[tip:x86/urgent] x86: Don' t rely on VMWare emulating PAT MSR correctly
From: tip-bot for Juergen Gross
Date: Tue Jan 20 2015 - 08:37:08 EST
Commit-ID: 9d34cfdf47963905d792ae9c000efa522739abe4
Gitweb: http://git.kernel.org/tip/9d34cfdf47963905d792ae9c000efa522739abe4
Author: Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Mon, 12 Jan 2015 06:15:45 +0100
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Tue, 20 Jan 2015 14:33:45 +0100
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 <jongman.heo@xxxxxxxxxxx>
Acked-by: Alok N Kataria <akataria@xxxxxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Link: http://lkml.kernel.org/r/1421039745-14335-1-git-send-email-jgross@xxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
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);
--
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