linux-kernel - Re: [PATCH] Fix i486 suspend to disk CR4 oops

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Date:	Mon, 18 Aug 2008 05:14:50 +0100 (BST)
From:	"Maciej W. Rozycki" <macro@...ux-mips.org>
To:	David Fries <david@...es.net>
cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix i486 suspend to disk CR4 oops

On Sun, 17 Aug 2008, David Fries wrote:

> arch/x86/power/cpu_32.c __save_processor_state calls read_cr4()
> only a i486 CPU doesn't have the CR4 register.  Trying to read it
> produces an invalid opcode oops during suspend to disk.
[...]
> diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c
> index 81e5ab6..bd0f2a3 100644
> --- a/arch/x86/kernel/acpi/sleep.c
> +++ b/arch/x86/kernel/acpi/sleep.c
> @@ -86,7 +86,9 @@ int acpi_save_state_mem(void)
>  #endif /* !CONFIG_64BIT */
>  
>  	header->pmode_cr0 = read_cr0();
> -	header->pmode_cr4 = read_cr4();
> +	/* cr4 was introduced in the Pentium CPU */
> +	if (boot_cpu_data.x86 >= 5)
> +		header->pmode_cr4 = read_cr4();
>  	header->realmode_flags = acpi_realmode_flags;
>  	header->real_magic = 0x12345678;
>  

 NACK.  Later i486 chips do have CR4 -- for PSE, VME, etc. (the set of
features varies across the line).  Use a fixup as elsewhere or something.

  Maciej
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