Messages in this thread | | | Date | Wed, 20 Dec 2000 03:47:10 +0100 | From | David Weinehall <> | Subject | Re: [PATCH] e820 memory detection fix for ThinkPad |
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On Tue, Dec 19, 2000 at 07:16:40PM -0500, Marc Joosen wrote: > > > Hi Alan, lkml-readers, > > This is a tiny patch to make the int15/e820 memory mapping work on IBM > ThinkPads. Until now, I have had to give lilo a mem= option with one meg > of RAM less than I actually have, so ACPI events don't overwrite any > data. The only alternative was to use one of the patches available on > http://www.pell.portland.or.us/~orc/Memory/, but these are quite big. I > tracked down the problem, at least for the ThinkPad 600X (2645-4EU), to > arch/i386/boot/setup.S: apparently the bios doesn't retain the value of > register %edx, so after the first entry is read the ascii word `SMAP' is > lost and further entries won't be recognized. The solution is simple, > just move the assignment 6 lines down so it's inside the loop that is > done for every entry. > This patch is for 2.4.0-test7..12, but it should work for pre13 > kernels and even 2.2 kernels with the memory map backport: > > --- linux/arch/i386/boot/setup.S.orig Sat Dec 9 05:56:07 2000 > +++ linux/arch/i386/boot/setup.S Sat Dec 9 06:43:03 2000 > @@ -292,7 +292,6 @@ > # > > meme820: > - movl $0x534d4150, %edx # ascii `SMAP' > xorl %ebx, %ebx # continuation counter > movw $E820MAP, %di # point into the whitelist > # so we can have the bios > @@ -300,6 +299,7 @@ > > jmpe820: > movl $0x0000e820, %eax # e820, upper word zeroed > + movl $0x534d4150, %edx # ascii `SMAP' > movl $20, %ecx # size of the e820rec > pushw %ds # data record. > popw %es
If this simple patch solves your problem, great! But in that case, PLEASE add a note telling WHY the assignment is done for every iteration; else some smarthead will probably submit a patch someday in the future along the lines of "assigning this only once makes the loop faster"...
Anyhow, good spotting!
Regards: David Weinehall _ _ // David Weinehall <tao@acc.umu.se> /> Northern lights wander \\ // Project MCA Linux hacker // Dance across the winter sky // \> http://www.acc.umu.se/~tao/ </ Full colour fire </ - 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/
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