Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753632Ab3GTMZH (ORCPT ); Sat, 20 Jul 2013 08:25:07 -0400 Received: from science.horizon.com ([71.41.210.146]:10979 "HELO science.horizon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752746Ab3GTMZG (ORCPT ); Sat, 20 Jul 2013 08:25:06 -0400 Date: 20 Jul 2013 08:25:04 -0400 Message-ID: <20130720122504.25856.qmail@science.horizon.com> From: "George Spelvin" To: hpa@linux.intel.com Subject: Re: [GIT PULL] x86 fixes for 3.11-rc2 Cc: linux@horizon.com, linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2836 Lines: 76 It's marginal with only two call sites, but would it be worth factoring out the write-back function? Something like this (untested) patch. It definitely makes the generated assembly cleaner. (Signed-off-by: George Spelvin if you want it.) diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h index cb75028..8802d97 100644 --- a/arch/x86/include/asm/msr.h +++ b/arch/x86/include/asm/msr.h @@ -171,6 +171,30 @@ static inline int wrmsr_safe(unsigned msr, unsigned low, unsigned high) __err; \ }) +/* + * We have to check that we can write back the value, and not just + * read it. At least on 90 nm Pentium M (Family 6, Model 13), reading + * an invalid MSR is not guaranteed to trap, see Erratum X4 in "Intel + * Pentium M Processor on 90 nm Process with 2-MB L2 Cache and Intel® + * Processor A100 and A110 on 90 nm process with 512-KB L2 Cache + * Specification Update". + */ +#define rdmsr_verysafe(msr, low, high) \ +({ \ + int __err; \ + asm volatile("2: rdmsr\n" \ + "3: wrmsr ; xor %[err],%[err]\n" \ + "1:\n\t" \ + ".section .fixup,\"ax\"\n\t" \ + "4: mov %[fault],%[err] ; jmp 1b\n\t" \ + ".previous\n\t" \ + _ASM_EXTABLE(2b, 4b) \ + _ASM_EXTABLE(3b, 4b) \ + : [err] "=r" (__err), "=a" (*low), "=d" (*high) \ + : "c" (msr), [fault] "i" (-EIO)); \ + __err; \ +}) + static inline int rdmsrl_safe(unsigned msr, unsigned long long *p) { int err; diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c index b44577b..7c3f40c 100644 --- a/arch/x86/kernel/acpi/sleep.c +++ b/arch/x86/kernel/acpi/sleep.c @@ -48,9 +48,9 @@ int acpi_suspend_lowlevel(void) #ifndef CONFIG_64BIT native_store_gdt((struct desc_ptr *)&header->pmode_gdt); - if (!rdmsr_safe(MSR_EFER, - &header->pmode_efer_low, - &header->pmode_efer_high)) + if (!rdmsr_verysafe(MSR_EFER, + &header->pmode_efer_low, + &header->pmode_efer_high)) header->pmode_behavior |= (1 << WAKEUP_BEHAVIOR_RESTORE_EFER); #endif /* !CONFIG_64BIT */ @@ -59,9 +59,9 @@ int acpi_suspend_lowlevel(void) header->pmode_cr4 = read_cr4(); header->pmode_behavior |= (1 << WAKEUP_BEHAVIOR_RESTORE_CR4); } - if (!rdmsr_safe(MSR_IA32_MISC_ENABLE, - &header->pmode_misc_en_low, - &header->pmode_misc_en_high)) + if (!rdmsr_verysafe(MSR_IA32_MISC_ENABLE, + &header->pmode_misc_en_low, + &header->pmode_misc_en_high)) header->pmode_behavior |= (1 << WAKEUP_BEHAVIOR_RESTORE_MISC_ENABLE); header->realmode_flags = acpi_realmode_flags; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/