Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751198AbdCQIss (ORCPT ); Fri, 17 Mar 2017 04:48:48 -0400 Received: from mail-wr0-f178.google.com ([209.85.128.178]:32941 "EHLO mail-wr0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751043AbdCQIsp (ORCPT ); Fri, 17 Mar 2017 04:48:45 -0400 Date: Fri, 17 Mar 2017 09:48:15 +0100 From: Christoffer Dall To: Suzuki K Poulose Cc: linux-arm-kernel@lists.infradead.org, andreyknvl@google.com, dvyukov@google.com, marc.zyngier@arm.com, christoffer.dall@linaro.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, kcc@google.com, syzkaller@googlegroups.com, will.deacon@arm.com, catalin.marinas@arm.com, pbonzini@redhat.com, mark.rutland@arm.com, ard.biesheuvel@linaro.org, stable@vger.kernel.org Subject: Re: [PATCH v2 3/3] kvm: arm/arm64: Fix locking for kvm_free_stage2_pgd Message-ID: <20170317084815.GU1277@cbox> References: <1489688451-17520-1-git-send-email-suzuki.poulose@arm.com> <1489688451-17520-4-git-send-email-suzuki.poulose@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1489688451-17520-4-git-send-email-suzuki.poulose@arm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2151 Lines: 57 On Thu, Mar 16, 2017 at 06:20:51PM +0000, Suzuki K Poulose wrote: > In kvm_free_stage2_pgd() we don't hold the kvm->mmu_lock while calling > unmap_stage2_range() on the entire memory range for the guest. This could > cause problems with other callers (e.g, munmap on a memslot) trying to > unmap a range. And since we have to unmap the entire Guest memory range > holding a spinlock, make sure we yield the lock if necessary, after we > unmap each PUD range. > > Fixes: commit d5d8184d35c9 ("KVM: ARM: Memory virtualization setup") > Cc: stable@vger.kernel.org # v3.10+ > Cc: Paolo Bonzini > Cc: Marc Zyngier > Cc: Christoffer Dall > Signed-off-by: Suzuki K Poulose > [ Avoid vCPU starvation and lockup detector warnings ] > Signed-off-by: Marc Zyngier > Signed-off-by: Suzuki K Poulose Reviewed-by: Christoffer Dall > --- > arch/arm/kvm/mmu.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c > index 13b9c1f..7628ef1 100644 > --- a/arch/arm/kvm/mmu.c > +++ b/arch/arm/kvm/mmu.c > @@ -292,8 +292,14 @@ static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size) > phys_addr_t addr = start, end = start + size; > phys_addr_t next; > > + assert_spin_locked(&kvm->mmu_lock); > pgd = kvm->arch.pgd + stage2_pgd_index(addr); > do { > + /* > + * If the range is too large, release the kvm->mmu_lock > + * to prevent starvation and lockup detector warnings. > + */ > + cond_resched_lock(&kvm->mmu_lock); > next = stage2_pgd_addr_end(addr, end); > if (!stage2_pgd_none(*pgd)) > unmap_stage2_puds(kvm, pgd, addr, next); > @@ -831,7 +837,10 @@ void kvm_free_stage2_pgd(struct kvm *kvm) > if (kvm->arch.pgd == NULL) > return; > > + spin_lock(&kvm->mmu_lock); > unmap_stage2_range(kvm, 0, KVM_PHYS_SIZE); > + spin_unlock(&kvm->mmu_lock); > + > /* Free the HW pgd, one page at a time */ > free_pages_exact(kvm->arch.pgd, S2_PGD_SIZE); > kvm->arch.pgd = NULL; > -- > 2.7.4 >