| Message ID | CAKv+Gu9mwj0qscQJSH8wEi0zYC0anrr1hBYbdFE83iN+oQLnRQ@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
On 8 March 2016 at 20:17, Mark Langsdorf <mlangsdo@redhat.com> wrote: > On 03/08/2016 04:31 AM, Ard Biesheuvel wrote: >> >> On 8 March 2016 at 09:15, Ard Biesheuvel <ard.biesheuvel@linaro.org> >> wrote: >>> >>> >>> >>>> On 8 mrt. 2016, at 08:07, David Daney <ddaney.cavm@gmail.com> wrote: >>>> >>>>> On 02/26/2016 08:57 AM, Ard Biesheuvel wrote: >>>>> Commit dd006da21646 ("arm64: mm: increase VA range of identity map") >>>>> made >>>>> some changes to the memory mapping code to allow physical memory to >>>>> reside >>>>> at an offset that exceeds the size of the virtual mapping. >>>>> >>>>> However, since the size of the vmemmap area is proportional to the size >>>>> of >>>>> the VA area, but it is populated relative to the physical space, we may >>>>> end up with the struct page array being mapped outside of the vmemmap >>>>> region. For instance, on my Seattle A0 box, I can see the following >>>>> output >>>>> in the dmesg log. >>>>> >>>>> vmemmap : 0xffffffbdc0000000 - 0xffffffbfc0000000 ( 8 GB >>>>> maximum) >>>>> 0xffffffbfc0000000 - 0xffffffbfd0000000 ( 256 MB >>>>> actual) >>>>> >>>>> We can fix this by deciding that the vmemmap region is not a projection >>>>> of >>>>> the physical space, but of the virtual space above PAGE_OFFSET, i.e., >>>>> the >>>>> linear region. This way, we are guaranteed that the vmemmap region is >>>>> of >>>>> sufficient size, and we can even reduce the size by half. >>>>> >>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> >>>> >>>> >>>> I see this commit now in Linus' kernel.org tree in v4.5-rc7. >>>> >>>> FYI: I am seeing a crash that goes away when I revert this. My kernel >>>> has some other modifications (our NUMA patches) so I haven't yet fully >>>> tracked this down on an unmodified kernel, but this is what I am getting: >>>> >>> >> >> I managed to reproduce and diagnose this. The problem is that vmemmap >> is no longer zone aligned, which causes trouble in the zone based >> rounding that occurs in memory_present. The below patch fixes this by >> rounding down the subtracted offset. Since this implies that the >> region could stick off the other end, it also reverts the halving of >> the region size. > > > This fixes the bug on my Seattle B0 system. > > Tested-by: Mark Langsdorf <mlangsdo@redhat.com> > Thanks Mark _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On 09.03.16 12:32:14, Robert Richter wrote: > On 08.03.16 17:31:05, Ard Biesheuvel wrote: > > On 8 March 2016 at 09:15, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote: > > I managed to reproduce and diagnose this. The problem is that vmemmap > > is no longer zone aligned, which causes trouble in the zone based > > rounding that occurs in memory_present. The below patch fixes this by > > rounding down the subtracted offset. Since this implies that the > > region could stick off the other end, it also reverts the halving of > > the region size. > > I have seen the same panic. The fix solves the problem. See enclosed > diff for reference as there was some patch corruption of the original. So this is: Tested-by: Robert Richter <rrichter@cavium.com> -Robert _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index f50608674580..ed57c0865290 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -40,7 +40,7 @@ * VMALLOC_END: extends to the available space below vmmemmap, PCI I/O space, * fixed mappings and modules */ -#define VMEMMAP_SIZE ALIGN((1UL << (VA_BITS - PAGE_SHIFT - 1)) * sizeof(struct page), PUD_SIZE) +#define VMEMMAP_SIZE ALIGN((1UL << (VA_BITS - PAGE_SHIFT)) * sizeof(struct page), PUD_SIZE)