From 6d7d28443969512be95873d2fb155f4be9261ca5 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Fri, 12 Jul 2013 16:48:12 -0700 Subject: [PATCH] x86, suspend: Handle CPUs which fail to #GP on RDMSR MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit commit 5ff560fd48d5b3d82fa0c3aff625c9da1a301911 upstream. There are CPUs which have errata causing RDMSR of a nonexistent MSR to not fault. We would then try to WRMSR to restore the value of that MSR, causing a crash. Specifically, some Pentium M variants would have this problem trying to save and restore the non-existent EFER, causing a crash on resume. Work around this by making sure we can write back the result at suspend time. Huge thanks to Christian Sünkenberg for finding the offending erratum that finally deciphered the mystery. Reported-and-tested-by: Johan Heinrich Debugged-by: Christian Sünkenberg Acked-by: Rafael J. Wysocki Link: http://lkml.kernel.org/r/51DDC972.3010005@student.kit.edu Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/acpi/sleep.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c index b44577bc9744..ec94e11807dc 100644 --- a/arch/x86/kernel/acpi/sleep.c +++ b/arch/x86/kernel/acpi/sleep.c @@ -48,9 +48,20 @@ int acpi_suspend_lowlevel(void) #ifndef CONFIG_64BIT native_store_gdt((struct desc_ptr *)&header->pmode_gdt); + /* + * 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". + */ if (!rdmsr_safe(MSR_EFER, &header->pmode_efer_low, - &header->pmode_efer_high)) + &header->pmode_efer_high) && + !wrmsr_safe(MSR_EFER, + header->pmode_efer_low, + header->pmode_efer_high)) header->pmode_behavior |= (1 << WAKEUP_BEHAVIOR_RESTORE_EFER); #endif /* !CONFIG_64BIT */ @@ -61,7 +72,10 @@ int acpi_suspend_lowlevel(void) } if (!rdmsr_safe(MSR_IA32_MISC_ENABLE, &header->pmode_misc_en_low, - &header->pmode_misc_en_high)) + &header->pmode_misc_en_high) && + !wrmsr_safe(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; -- 2.39.5