On Thu, May 15, 2014 at 10:19:22AM -0400, Mark Salter wrote: > The following happens when trying to run a kvm guest on a kernel > configured for 64k pages. This doesn't happen with 4k pages: > > BUG: failure at include/linux/mm.h:297/put_page_testzero()! > Kernel panic - not syncing: BUG! > CPU: 2 PID: 4228 Comm: qemu-system-aar Tainted: GF > 3.13.0-0.rc7.31.sa2.k32v1.aarch64.debug #1 > Call trace: > [<fffffe0000096034>] dump_backtrace+0x0/0x16c > [<fffffe00000961b4>] show_stack+0x14/0x1c > [<fffffe000066e648>] dump_stack+0x84/0xb0 > [<fffffe0000668678>] panic+0xf4/0x220 > [<fffffe000018ec78>] free_reserved_area+0x0/0x110 > [<fffffe000018edd8>] free_pages+0x50/0x88 > [<fffffe00000a759c>] kvm_free_stage2_pgd+0x30/0x40 > [<fffffe00000a5354>] kvm_arch_destroy_vm+0x18/0x44 > [<fffffe00000a1854>] kvm_put_kvm+0xf0/0x184 > [<fffffe00000a1938>] kvm_vm_release+0x10/0x1c > [<fffffe00001edc1c>] __fput+0xb0/0x288 > [<fffffe00001ede4c>] ____fput+0xc/0x14 > [<fffffe00000d5a2c>] task_work_run+0xa8/0x11c > [<fffffe0000095c14>] do_notify_resume+0x54/0x58 > > 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.
Hi Mark, I'm still catching up with myself, sorry (was off sick for a couple of days)... I thought unmap_range was going to be changed? Does the following help things? https://lists.cs.columbia.edu/pipermail/kvmarm/2014-May/009388.html Cheers, -- Steve > > Signed-off-by: Mark Salter <msal...@redhat.com> > --- > arch/arm64/mm/hugetlbpage.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c > index 5e9aec3..9bed38f 100644 > --- a/arch/arm64/mm/hugetlbpage.c > +++ b/arch/arm64/mm/hugetlbpage.c > @@ -51,7 +51,11 @@ int pmd_huge(pmd_t pmd) > > int pud_huge(pud_t pud) > { > +#ifndef __PAGETABLE_PMD_FOLDED > return !(pud_val(pud) & PUD_TABLE_BIT); > +#else > + return 0; > +#endif > } > > int pmd_huge_support(void) > @@ -64,8 +68,10 @@ static __init int setup_hugepagesz(char *opt) > unsigned long ps = memparse(opt, &opt); > if (ps == PMD_SIZE) { > hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT); > +#ifndef __PAGETABLE_PMD_FOLDED > } else if (ps == PUD_SIZE) { > hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT); > +#endif > } else { > pr_err("hugepagesz: Unsupported page size %lu M\n", ps >> 20); > return 0; > -- > 1.9.0 > -- 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/
