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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 bd809af16e 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: bd809af16e "x86: Enable PAT to use cache mode translation tables"
Reported-and-tested-by: Jongman Heo <jongman.heo@samsung.com>
Acked-by: Alok N Kataria <akataria@vmware.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Link: http://lkml.kernel.org/r/1421039745-14335-1-git-send-email-jgross@suse.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Juergen Gross 2015-01-12 06:15:45 +01:00 committed by Thomas Gleixner
parent 4a0d3107d6
commit 9d34cfdf47
1 changed files with 6 additions and 1 deletions
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7
arch/x86/mm/pat.c
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@ -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);