From 4797ec2dc83a43be35bad56037d1b53db9e2b5d5 Mon Sep 17 00:00:00 2001 From: Mark Salter Date: Thu, 15 May 2014 15:19:22 +0100 Subject: [PATCH] arm64: fix pud_huge() for 2-level pagetables 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: [] dump_backtrace+0x0/0x16c [] show_stack+0x14/0x1c [] dump_stack+0x84/0xb0 [] panic+0xf4/0x220 [] free_reserved_area+0x0/0x110 [] free_pages+0x50/0x88 [] kvm_free_stage2_pgd+0x30/0x40 [] kvm_arch_destroy_vm+0x18/0x44 [] kvm_put_kvm+0xf0/0x184 [] kvm_vm_release+0x10/0x1c [] __fput+0xb0/0x288 [] ____fput+0xc/0x14 [] task_work_run+0xa8/0x11c [] 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: Mark Salter [catalin.marinas@arm.com: removed #ifndef around PUD_SIZE check] Signed-off-by: Catalin Marinas Cc: # v3.11+ --- arch/arm64/mm/hugetlbpage.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c index 5e9aec358306..31eb959e9aa8 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) -- 2.34.1