Messages in this thread | | | Subject | Re: [PATCH] arm64: fix pud_huge() for 2-level pagetables | From | Mark Salter <> | Date | Thu, 15 May 2014 12:27:38 -0400 |
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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: > > 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
No, I get the same BUG. Regardless, pud_huge() should always return false for 2-level pagetables, right?
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