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 4.14-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-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit e755100091db3549d3f9d31ed0ba9136d311ac1e
Author: Will Deacon <will@xxxxxxxxxx>
Date: Mon Aug 24 12:29:54 2020 +0100
KVM: arm/arm64: Don't reschedule in unmap_stage2_range()
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> # v4.14 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>
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 3814cdad643a5..7fe673248e984 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -307,12 +307,6 @@ static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size)
next = stage2_pgd_addr_end(addr, end);
if (!stage2_pgd_none(*pgd))
unmap_stage2_puds(kvm, pgd, addr, next);
- /*
- * If the range is too large, release the kvm->mmu_lock
- * to prevent starvation and lockup detector warnings.
- */
- if (next != end)
- cond_resched_lock(&kvm->mmu_lock);
} while (pgd++, addr = next, addr != end);
}
