Messages in this thread | | | Date | Fri, 15 Feb 2008 21:41:28 +0100 | From | "Oliver Pinter" <> | Subject | Re: [patch 1/3] x86_64: CPA, fix cache attribute inconsistency bug, v2.6.22 backport |
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hi Ingo,
thx add to http://repo.or.cz/w/linux-2.6.22.y-op.git testing ;)
On 2/15/08, Ingo Molnar <mingo@elte.hu> wrote: > > fix CPA cache attribute bug in v2.6.23. When phys_base is nonzero > (when CONFIG_RELOCATABLE=y) then change_page_attr_addr() miscalculates > the secondary alias address by -14 MB (depending on the configured > offset). > > The default 64-bit kernels of Fedora and Ubuntu are affected: > > $ grep RELOCA /boot/config-2.6.23.9-85.fc8 > CONFIG_RELOCATABLE=y > > $ grep RELOC /boot/config-2.6.22-14-generic > CONFIG_RELOCATABLE=y > > and probably on many other distros as well. > > the bug affects all pages in the first 40 MB of physical RAM that > are allocated by some subsystem that does ioremap_nocache() on them: > > if (__pa(address) < KERNEL_TEXT_SIZE) { > > Hence we might leave page table entries with inconsistent cache > attributes around (pages mapped at both UnCacheable and Write-Back), > and we can also set the wrong kernel text pages to UnCacheable. > > the effects of this bug can be random slowdowns and other misbehavior. > If for example AGP allocates its aperture pages into the first 40 MB > of physical RAM, then the -14 MB bug might mark random kernel texto > pages as uncacheable, slowing down a random portion of the 64-bit > kernel until the AGP driver is unloaded. > > Signed-off-by: Ingo Molnar <mingo@elte.hu> > Acked-by: Thomas Gleixner <tglx@linutronix.de> > --- > arch/x86_64/mm/pageattr.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > Index: linux-tmp/arch/x86_64/mm/pageattr.c > =================================================================== > --- linux-tmp.orig/arch/x86_64/mm/pageattr.c > +++ linux-tmp/arch/x86_64/mm/pageattr.c > @@ -204,7 +204,7 @@ int change_page_attr_addr(unsigned long > if (__pa(address) < KERNEL_TEXT_SIZE) { > unsigned long addr2; > pgprot_t prot2; > - addr2 = __START_KERNEL_map + __pa(address); > + addr2 = __START_KERNEL_map + __pa(address) - phys_base; > /* Make sure the kernel mappings stay executable */ > prot2 = pte_pgprot(pte_mkexec(pfn_pte(0, prot))); > err = __change_page_attr(addr2, pfn, prot2, > -- > 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/ > -- Thanks, Oliver
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