From 224bb1e5d67ba0f2872c98002d6a6f991ac6fd4a Mon Sep 17 00:00:00 2001 From: Toshi Kani Date: Wed, 23 Mar 2016 15:41:58 -0600 Subject: [PATCH] x86/mm/pat: Add pat_disable() interface In preparation for fixing a regression caused by: 9cd25aac1f44 ("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 Reviewed-by: Thomas Gleixner Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Juergen Gross Cc: Linus Torvalds Cc: Luis R. Rodriguez Cc: Peter Zijlstra Cc: Robert Elliott Cc: Toshi Kani 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 --- arch/x86/include/asm/pat.h | 1 + arch/x86/mm/pat.c | 13 ++++++++++++- 2 files changed, 13 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/pat.h b/arch/x86/include/asm/pat.h index 97ea55bc2b54..0ad356c066ef 100644 --- a/arch/x86/include/asm/pat.h +++ b/arch/x86/include/asm/pat.h @@ -5,6 +5,7 @@ #include bool pat_enabled(void); +void pat_disable(const char *reason); extern void pat_init(void); void __init_cache_modes(u64); diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c index b4663885308f..1cc1d37f1de7 100644 --- a/arch/x86/mm/pat.c +++ b/arch/x86/mm/pat.c @@ -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) -- 2.20.1