On Thu, May 15, 2014 at 07:39:17PM +0100, Mark Salter wrote: > On Thu, 2014-05-15 at 18:55 +0100, Steve Capper wrote: > > On 15 May 2014 17:27, Mark Salter <msal...@redhat.com> wrote: > > > On Thu, 2014-05-15 at 15:44 +0100, Steve Capper wrote: > > >> On Thu, May 15, 2014 at 10:19:22AM -0400, Mark Salter wrote: > > >> > In arch/arm/kvm/mmu.c:unmap_range(), we end up doing an extra > > >> > put_page() > > >> > on the stage2 pgd which leads to the BUG in put_page_testzero(). This > > >> > happens because a pud_huge() test in unmap_range() returns true when it > > >> > should always be false with 2-level pages tables used by 64k pages. > > >> > This patch removes support for huge puds if 2-level pagetables are > > >> > being used. [...] > > Yeah I agree for 64K granule it doesn't make sense to have a huge_pud. > > The patch looks sound now, but checking for a folded pmd may run into > > problems if/when we get to 3-levels and 64K pages in future. > > > > Perhaps checking for PAGE_SHIFT==12 (or something similar) would be a > > bit more robust? > > I don't think testing based on granule size is generally correct either. > Maybe support for 3-level page tables with 64k granule gets added as an > option. That would break the pagesize based test. With a folded pmd, we > know there is no pud, so pud_huge() should always be false.
I agree, pud_huge() should be false in the same way we define pud_present() to be 1 when __PGTABLE_PMD_FOLDED. The *_huge() macros aren't covered by the generic headers unfortunately (some clean-up would be useful at some point but for now this patch is fine). -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
