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 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>

1 files changed, 10 insertions, 0 deletions

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 17c946369c88..2fd5c135e8a4 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -292,11 +292,18 @@ static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size)
         phys_addr_t addr = start, end = start + size;
         phys_addr_t next;
 
+        assert_spin_locked(&kvm->mmu_lock);
         pgd = kvm->arch.pgd + stage2_pgd_index(addr);
         do {
                 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);
 }
 
@@ -831,7 +838,10 @@ 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);
+
         /* Free the HW pgd, one page at a time */
         free_pages_exact(kvm->arch.pgd, S2_PGD_SIZE);
         kvm->arch.pgd = NULL;