Commit 2a60bb63 authored Apr 03, 2017 by Suzuki K Poulose Committed by Greg Kroah-Hartman Apr 27, 2017

kvm: arm/arm64: Fix locking for kvm_free_stage2_pgd



commit 8b3405e345b5a098101b0c31b264c812bba045d9 upstream.

In kvm_free_stage2_pgd() we don't hold the kvm->mmu_lock while calling
unmap_stage2_range() on the entire memory range for the guest. This could
cause problems with other callers (e.g, munmap on a memslot) trying to
unmap a range. And since we have to unmap the entire Guest memory range
holding a spinlock, make sure we yield the lock if necessary, after we
unmap each PUD range.

Fixes: commit d5d8184d ("KVM: ARM: Memory virtualization setup")
Cc: Paolo Bonzini <pbonzin@redhat.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
[ Avoid vCPU starvation and lockup detector warnings ]
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Christoffer Dall <cdall@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent e2587fba

arch/arm/kvm/mmu.c

+12 −0

Original line number	Diff line number	Diff line
		@@ -300,6 +300,14 @@ 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);
		}

		@@ -738,6 +746,7 @@ int kvm_alloc_stage2_pgd(struct kvm *kvm)
		*/
		static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size)
		{
		assert_spin_locked(&kvm->mmu_lock);
		unmap_range(kvm, kvm->arch.pgd, start, size);
		}

		@@ -824,7 +833,10 @@ void kvm_free_stage2_pgd(struct kvm *kvm)
		if (kvm->arch.pgd == NULL)
		return;

		spin_lock(&kvm->mmu_lock);
		unmap_stage2_range(kvm, 0, KVM_PHYS_SIZE);
		spin_unlock(&kvm->mmu_lock);

		kvm_free_hwpgd(kvm_get_hwpgd(kvm));
		if (KVM_PREALLOC_LEVEL > 0)
		kfree(kvm->arch.pgd);