x86, suspend: Handle CPUs which fail to #GP on RDMSR (5ff560fd) · Commits · 戴 / test

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 <onny@project-insanity.org> Debugged-by:

Christian Sünkenberg <christian.suenkenberg@student.kit.edu> Acked-by:

Rafael J. Wysocki <rjw@sisk.pl> Link: http://lkml.kernel.org/r/51DDC972.3010005@student.kit.edu Cc: <stable@vger.kernel.org> # v3.7+

arch/x86/kernel/acpi/sleep.c

+16 −2

Original line number	Diff line number	Diff line
		@@ -48,9 +48,20 @@ int x86_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 x86_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;

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