kvm: arm/arm64: Fix locking for kvm_free_stage2_pgd

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: stable@vger.kernel.org # v3.10+
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>

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 13b9c1fa8961b42ca672ffcb752fb3943b2f6916..582a972371cf886b8581de1abcfe609a53540245 100644 (file)
--- 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;