This is a note to let you know that I've just added the patch titled KVM: arm/arm64: Don't reschedule in unmap_stage2_range() to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-arm-arm64-don-t-reschedule-in-unmap_stage2_range.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From will@xxxxxxxxxx Mon Aug 24 18:14:45 2020 From: Will Deacon <will@xxxxxxxxxx> Date: Mon, 24 Aug 2020 12:28:54 +0100 Subject: KVM: arm/arm64: Don't reschedule in unmap_stage2_range() To: gregkh@xxxxxxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx, maz@xxxxxxxxxx, suzuki.poulose@xxxxxxx, james.morse@xxxxxxx, pbonzini@xxxxxxxxxx, kernel-team@xxxxxxxxxxx, Will Deacon <will@xxxxxxxxxx>, stable@xxxxxxxxxxxxxxx Message-ID: <20200824112854.24651-1-will@xxxxxxxxxx> From: Will Deacon <will@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx> # v4.4 only Cc: Marc Zyngier <maz@xxxxxxxxxx> Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx> Cc: James Morse <james.morse@xxxxxxx> Signed-off-by: Will Deacon <will@xxxxxxxxxx> Acked-by: Marc Zyngier <maz@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/arm/kvm/mmu.c | 8 -------- 1 file changed, 8 deletions(-) --- a/arch/arm/kvm/mmu.c +++ b/arch/arm/kvm/mmu.c @@ -300,14 +300,6 @@ static void unmap_range(struct kvm *kvm, next = kvm_pgd_addr_end(addr, end); if (!pgd_none(*pgd)) unmap_puds(kvm, pgd, addr, next); - /* - * If we are dealing with a large range in - * stage2 table, release the kvm->mmu_lock - * to prevent starvation and lockup detector - * warnings. - */ - if (kvm && (next != end)) - cond_resched_lock(&kvm->mmu_lock); } while (pgd++, addr = next, addr != end); } Patches currently in stable-queue which might be from will@xxxxxxxxxx are queue-4.4/kvm-arm-arm64-don-t-reschedule-in-unmap_stage2_range.patch