linux-kernel - Re: [PATCH stable-4.4.y backport] KVM: arm/arm64: Don't reschedule in unmap_stage2

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Date:   Mon, 24 Aug 2020 18:16:50 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Will Deacon <will@...nel.org>
Cc:     linux-kernel@...r.kernel.org, maz@...nel.org,
        suzuki.poulose@....com, james.morse@....com, pbonzini@...hat.com,
        kernel-team@...roid.com, stable@...r.kernel.org
Subject: Re: [PATCH stable-4.4.y backport] KVM: arm/arm64: Don't reschedule
 in unmap_stage2_range()

On Mon, Aug 24, 2020 at 12:28:54PM +0100, Will Deacon wrote:
> Upstream commits fdfe7cbd5880 ("KVM: Pass MMU notifier range flags to
> kvm_unmap_hva_range()") and b5331379bc62 ("KVM: arm64: Only reschedule
> if MMU_NOTIFIER_RANGE_BLOCKABLE is not set") fix a "sleeping from invalid
> context" BUG caused by unmap_stage2_range() attempting to reschedule when
> called on the OOM path.
> 
> Unfortunately, these patches rely on the MMU notifier callback being
> passed knowledge about whether or not blocking is permitted, which was
> introduced in 4.19. Rather than backport this considerable amount of
> infrastructure just for KVM on arm, instead just remove the conditional
> reschedule.
> 
> Cc: <stable@...r.kernel.org> # v4.4 only
> Cc: Marc Zyngier <maz@...nel.org>
> Cc: Suzuki K Poulose <suzuki.poulose@....com>
> Cc: James Morse <james.morse@....com>
> Signed-off-by: Will Deacon <will@...nel.org>

Thanks for tall the backports, now queued up.

greg k-h