Commit 9d34cfdf authored by Juergen Gross's avatar Juergen Gross Committed by Thomas Gleixner

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 bd809af1 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: bd809af1 "x86: Enable PAT to use cache mode translation tables"
Reported-and-tested-by: default avatarJongman Heo <>
Acked-by: default avatarAlok N Kataria <>
Signed-off-by: default avatarJuergen Gross <>
Link: default avatarThomas Gleixner <>
parent 4a0d3107
......@@ -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.");
wrmsrl(MSR_IA32_CR_PAT, pat);
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