[PATCH 4.4 20/28] kvm: arm/arm64: Fix locking for kvm_free_stage2_pgd

Greg Kroah-Hartman
2017-04-25T15:34:24Z

From: Suzuki K Poulose <suzuki.poulose@arm.com>

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 d5d8184d35c9 ("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>

---
arch/arm/kvm/mmu.c | 12 ++++++++++++
1 file changed, 12 insertions(+)

--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -300,6 +300,14 @@ 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);
}

@@ -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);