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 4.4-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-4.4 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 | 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);
Patches currently in stable-queue which might be from suzuki.poulose@xxxxxxx are
queue-4.4/kvm-arm-arm64-fix-locking-for-kvm_free_stage2_pgd.patch