Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 26 Dec 2000 16:11:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 26 Dec 2000 16:11:25 -0500 Received: from [194.213.32.137] ([194.213.32.137]:22789 "EHLO bug.ucw.cz") by vger.kernel.org with ESMTP id ; Tue, 26 Dec 2000 16:11:09 -0500 Message-ID: <20001226213833.A628@bug.ucw.cz> Date: Tue, 26 Dec 2000 21:38:33 +0100 From: Pavel Machek To: Kai Henningsen , linux-kernel@vger.kernel.org Subject: Re: About Celeron processor memory barrier problem In-Reply-To: <7sSHLPCmw-B@khms.westfalen.de>

<7sSHLPCmw-B@khms.westfalen.de> <20001224125023.A1900@scutter.internal.splhi.com> <7sX4YyEmw-B@khms.westfalen.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.93i In-Reply-To: <7sX4YyEmw-B@khms.westfalen.de>; from Kai Henningsen on Mon, Dec 25, 2000 at 01:12:00PM +0200 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > On Sun, Dec 24, 2000 at 11:36:00AM +0200, Kai Henningsen wrote: > > > There was a similar thread to this recently. The issue is that if you > > choose the wrong processor type, you may not even be able to complain. > > Hmm ... I think I can see ways around that (essentially similar to the 16 > bit bootstrap code), but it may indeed be more trouble than it's worth. Actually we are doing cpu detection during "uncompress" stage on x86-64. Here's how we do it: You might consider something similar. Pavel --- arch/i386/boot/compressed/misc.c Mon Nov 20 23:50:36 2000 +++ arch/x86_64/boot/compressed/misc.c Mon Nov 13 21:10:26 2000 @@ -8,6 +8,7 @@ * puts by Nick Holloway 1993, better puts by Martin Mares 1995 * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996 */ +asm(".code32"); #include #include @@ -340,6 +341,75 @@ } } +void check_cpu(void) +{ + int res = 0; + asm volatile( " \n\ + movl $3,%%edx # at least 386 \n\ + pushfl # push EFLAGS \n\ + popl %%eax # get EFLAGS \n\ + movl %%eax,%%ecx # save original EFLAGS \n\ + xorl $0x40000,%%eax # flip AC bit in EFLAGS \n\ + pushl %%eax # copy to EFLAGS \n\ + popfl # set EFLAGS \n\ + pushfl # get new EFLAGS \n\ + popl %%eax # put it in eax \n\ + xorl %%ecx,%%eax # change in flags \n\ + andl $0x40000,%%eax # check if AC bit changed \n\ + je 1f \n\ +\n\ + movl $4,%%edx # at least 486 \n\ + movl %%ecx,%%eax \n\ + xorl $0x200000,%%eax # check ID flag \n\ + pushl %%eax \n\ + popfl # if we are on a straight 486DX, SX, or \n\ + pushfl # 487SX we can't change it \n\ + popl %%eax \n\ + xorl %%ecx,%%eax \n\ + pushl %%ecx # restore original EFLAGS \n\ + popfl \n\ + andl $0x200000,%%eax \n\ + je 1f \n\ +\n\ + /* get vendor info */ \n\ +# xorl %%eax,%%eax # call CPUID with 0 -> return vendor ID \n\ +# cpuid \n\ +# movl $5, %%edx \n\ +# cmpl $0x41757468,%%ebx # check thats amd \n\ +# jne 1f \n\ +\n\ + mov $0x80000000,%%eax\n\ # Is extended cpuid supported? + cpuid\n\ + test %%eax,0x80000000\n\ + movl $5, %%edx \n\ + jz 1f\n\ +\n\ + movl $0x80000001,%%eax \n\ + cpuid \n\ + andl $0x20000000,%%edx \n\ + movl $6, %%edx \n\ + jz 1f \n\ +\n\ + movl $7, %%edx \n\ +1:" : "=d" (res) : : "eax", "ebx", "ecx" ); + + switch (res) { + case 3: puts( "386" ); + break; + case 4: puts( "486" ); + break; + case 5: puts( "no extended cpuid" ); + break; + case 6: puts( "non-64bit 586+" ); + break; + case 7: puts( "64bit" ); + break; + default:puts( "internal error" ); + break; + } + if (res !=7) + error( "Sorry, your CPU is not capable of running 64-bit kernel." ); +} int decompress_kernel(struct moveparams *mv, void *rmode) { @@ -360,7 +430,9 @@ else setup_output_buffer_if_we_run_high(mv); makecrc(); - puts("Uncompressing Linux... "); + puts("Checking CPU type... "); + check_cpu(); + puts(", uncompressing Linux... "); gunzip(); puts("Ok, booting the kernel.\n"); if (high_loaded) close_output_buffer_if_we_run_high(mv); -- I'm pavel@ucw.cz. "In my country we have almost anarchy and I don't care." Panos Katsaloulis describing me w.r.t. patents at discuss@linmodems.org - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/