Commit 9d34cfdf authored Jan 12, 2015 by Juergen Gross Committed by Thomas Gleixner Jan 20, 2015

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: 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>

parent 4a0d3107

arch/x86/mm/pat.c

+6 −1

Original line number	Original line	Diff line number	Diff line
	@@ -234,8 +234,13 @@ void pat_init(void)
	PAT(4, WB) \| PAT(5, WC) \| PAT(6, UC_MINUS) \| PAT(7, UC);		PAT(4, WB) \| PAT(5, WC) \| PAT(6, UC_MINUS) \| PAT(7, UC);

	/* Boot CPU check */		/* Boot CPU check */
	if (!boot_pat_state)		if (!boot_pat_state) {
	rdmsrl(MSR_IA32_CR_PAT, 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);		wrmsrl(MSR_IA32_CR_PAT, pat);