Commit 224bb1e5 authored Mar 23, 2016 by Toshi Kani Committed by Ingo Molnar Mar 29, 2016

x86/mm/pat: Add pat_disable() interface



In preparation for fixing a regression caused by:

  9cd25aac ("x86/mm/pat: Emulate PAT when it is disabled")

... PAT needs to provide an interface that prevents the OS from
initializing the PAT MSR.

PAT MSR initialization must be done on all CPUs using the specific
sequence of operations defined in the Intel SDM.  This requires MTRRs
to be enabled since pat_init() is called as part of MTRR init
from mtrr_rendezvous_handler().

Make pat_disable() as the interface that prevents the OS from
initializing the PAT MSR.  MTRR will call this interface when it
cannot provide the SDM-defined sequence to initialize PAT.

This also assures that pat_disable() called from pat_bsp_init()
will set the PAT table properly when CPU does not support PAT.

Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Robert Elliott <elliott@hpe.com>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: konrad.wilk@oracle.com
Cc: paul.gortmaker@windriver.com
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1458769323-24491-3-git-send-email-toshi.kani@hpe.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 02f037d6

arch/x86/include/asm/pat.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -5,6 +5,7 @@
		#include <asm/pgtable_types.h>

		bool pat_enabled(void);
		void pat_disable(const char *reason);
		extern void pat_init(void);
		void __init_cache_modes(u64);

arch/x86/mm/pat.c

+12 −1

Original line number	Diff line number	Diff line
		@@ -40,11 +40,22 @@
		static bool boot_cpu_done;

		static int __read_mostly __pat_enabled = IS_ENABLED(CONFIG_X86_PAT);
		static void init_cache_modes(void);

		static inline void pat_disable(const char *reason)
		void pat_disable(const char *reason)
		{
		if (!__pat_enabled)
		return;

		if (boot_cpu_done) {
		WARN_ONCE(1, "x86/PAT: PAT cannot be disabled after initialization\n");
		return;
		}

		__pat_enabled = 0;
		pr_info("x86/PAT: %s\n", reason);

		init_cache_modes();
		}

		static int __init nopat(char *str)

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