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x86: Don't rely on VMWare emulating PAT MSR correctly

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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 <[email protected]>
Acked-by: Alok N Kataria <[email protected]>
Signed-off-by: Juergen Gross <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>
This commit is contained in:
Juergen Gross authored and Thomas Gleixner committed 2015-01-20 14:33:45 +01:00
1 parent 4a0d3107d6
commit 9d34cfdf47
1 file changed
+6 -1
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arch/x86/mm/pat.c
+6 -1
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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);