linux-kernel - [PATCH 0/2] KVM: arm64: Fix sleeping while atomic BUG() on OOM

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Date:   Tue, 11 Aug 2020 11:27:23 +0100
From:   Will Deacon <will@...nel.org>
To:     kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        James Morse <james.morse@....com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Paul Mackerras <paulus@...abs.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: [PATCH 0/2] KVM: arm64: Fix sleeping while atomic BUG() on OOM

Hi all,

While stress-testing my arm64 stage-2 page-table rewrite [1], I ran into
a sleeping while atomic BUG() during OOM that I can reproduce with
mainline.

The problem is that the arm64 page-table code periodically calls
cond_resched_lock() when unmapping the stage-2 page-tables, but in the
case of OOM, this occurs in atomic context.

These couple of patches (based on 5.8) propagate the flags from the MMU
notifier range structure, which in turn indicate whether or not blocking
is permitted.

Cheers,

Will

[1] https://android-kvm.googlesource.com/linux/+/refs/heads/topic/pgtable

Cc: Marc Zyngier <maz@...nel.org>
Cc: Suzuki K Poulose <suzuki.poulose@....com>
Cc: James Morse <james.morse@....com>
Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc: Paul Mackerras <paulus@...abs.org>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Sean Christopherson <sean.j.christopherson@...el.com>

--->8

Will Deacon (2):
  KVM: Pass MMU notifier range flags to kvm_unmap_hva_range()
  KVM: arm64: Only reschedule if MMU_NOTIFIER_RANGE_BLOCKABLE is not set

 arch/arm64/include/asm/kvm_host.h   |  2 +-
 arch/arm64/kvm/mmu.c                | 19 ++++++++++++++-----
 arch/mips/include/asm/kvm_host.h    |  2 +-
 arch/mips/kvm/mmu.c                 |  3 ++-
 arch/powerpc/include/asm/kvm_host.h |  3 ++-
 arch/powerpc/kvm/book3s.c           |  3 ++-
 arch/powerpc/kvm/e500_mmu_host.c    |  3 ++-
 arch/x86/include/asm/kvm_host.h     |  3 ++-
 arch/x86/kvm/mmu/mmu.c              |  3 ++-
 virt/kvm/kvm_main.c                 |  3 ++-
 10 files changed, 30 insertions(+), 14 deletions(-)

-- 
2.28.0.236.gb10cc79966-goog