x86: Don't rely on VMWare emulating PAT MSR correctly
authorJuergen Gross <jgross@suse.com>
Mon, 12 Jan 2015 05:15:45 +0000 (06:15 +0100)
committerThomas Gleixner <tglx@linutronix.de>
Tue, 20 Jan 2015 13:33:45 +0000 (14:33 +0100)
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@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>
arch/x86/mm/pat.c

index edf299c8ff6c774dea8116092a41b15102d9cf1c..7ac68698406c3b35e5ce0b0e98c73c5441e869a3 100644 (file)
@@ -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);