Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753998AbYHRGFG (ORCPT ); Mon, 18 Aug 2008 02:05:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750986AbYHRGE4 (ORCPT ); Mon, 18 Aug 2008 02:04:56 -0400 Received: from one.firstfloor.org ([213.235.205.2]:53823 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750885AbYHRGEz (ORCPT ); Mon, 18 Aug 2008 02:04:55 -0400 To: "H. Peter Anvin" Cc: "Maciej W. Rozycki" , David Fries , linux-kernel@vger.kernel.org Subject: Re: [PATCH] Fix i486 suspend to disk CR4 oops From: Andi Kleen References: <20080818040340.GB17528@spacedout.fries.net> <48A8FC21.9060908@zytor.com> Date: Mon, 18 Aug 2008 08:04:51 +0200 In-Reply-To: <48A8FC21.9060908@zytor.com> (H. Peter Anvin's message of "Sun, 17 Aug 2008 21:35:45 -0700") Message-ID: <87skt2270c.fsf@basil.nowhere.org> User-Agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/21.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1497 Lines: 39 "H. Peter Anvin" writes: > Maciej W. Rozycki wrote: >> 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. >> > > The other alternative is to probe for the CPUID instruction (via > EFLAGS.ID) -- CR4 is present if and only if CPUID exists. Can be already checked for with boot_cpu_data.extended_cpuid_level. -Andi -- 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/