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SubjectRe: Athlon/VIA Kernel Experimentation (mmx.c)
Seth Goldberg wrote:
>
> Hi,
>
> I implemented a small check loop at the end of the fast_page_copy
> routine in mmx.c for the Athlon. Booting the resulting kernel
> yields an interesting result. Every single time, the kernel
> panics RIGHT AFTER it frees unused kernel memory from bootup.
> I encourage those of you with the same problem to try this and report
> when it panics.
>
> Here is my patch to mmx.c: (sorry about the long lines)
> -----------------------------------------------------cut here
> diff -r linux-ref/arch/i386/lib/mmx.c linux/arch/i386/lib/mmx.c
> 204a205,216
> >
> > {
> > register int x = 0;
> > /* do mem compares to ensure written == read */
> > for ( /* initted above */; x < (4096/sizeof(int)); x++ )
> > {
> > if ( ((int *)to)[x] != ((int *)from)[x] ) {
> > panic("fast_page_copy: dest value @ 0x%lx (%x) does not equal source value @ %lx (%x)!\n",
> > (long) to, ((int *)to)[x], (long) from, ((int *) from)[x] );
> > }
> > }
> > }
> -----------------------------------------------------cut here
>
> Wouldn't it be correct to say that because it is panicking, the
> page copy was not completed properly?

No, you are comparing the following two pages... from and to are
incremented as the copy proceeds. Subtract PAGE_SIZE from them before
comparing.

--

Brian Gerst
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