• Mark Salter's avatar
    arm64: fix pud_huge() for 2-level pagetables · 4797ec2d
    Mark Salter authored
    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.
    Signed-off-by: default avatarMark Salter <msalter@redhat.com>
    [catalin.marinas@arm.com: removed #ifndef around PUD_SIZE check]
    Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
    Cc: <stable@vger.kernel.org> # v3.11+
    4797ec2d
hugetlbpage.c 1.87 KB