This is a note to let you know that I've just added the patch titled
kvm: arm/arm64: Fix locking for kvm_free_stage2_pgd
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-arm-arm64-fix-locking-for-kvm_free_stage2_pgd.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 8b3405e345b5a098101b0c31b264c812bba045d9 Mon Sep 17 00:00:00 2001
From: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Date: Mon, 3 Apr 2017 15:12:43 +0100
Subject: kvm: arm/arm64: Fix locking for kvm_free_stage2_pgd
From: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
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@xxxxxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
[ Avoid vCPU starvation and lockup detector warnings ]
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Signed-off-by: Christoffer Dall <cdall@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/kvm/mmu.c | 10 ++++++++++
1 file changed, 10 insertions(+)
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -292,11 +292,18 @@ static void unmap_stage2_range(struct kv
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;
Patches currently in stable-queue which might be from suzuki.poulose@xxxxxxx are
queue-4.9/kvm-arm-arm64-fix-locking-for-kvm_free_stage2_pgd.patch
queue-4.9/arm-arm64-kvm-take-mmap_sem-in-kvm_arch_prepare_memory_region.patch
queue-4.9/arm-arm64-kvm-take-mmap_sem-in-stage2_unmap_vm.patch