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@vger.kernel.org> # v4.4 only
Cc: Marc Zyngier <maz@kernel.org>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: James Morse <james.morse@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
Acked-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index e0267532bd4e0f9d705d804dd16e437d72b699f8..edd392fdc14bb44a0afffa0cffadc7e06527af03 100644 (file)
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -300,14 +300,6 @@ static void unmap_range(struct kvm *kvm, pgd_t *pgdp,
                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);
 }