On 16/07/17 14:56, Ben Hutchings wrote:
3.16.46-rc1 review patch. If anyone has any objections, please let me know.
------------------
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>
[bwh: Backported to 3.16:
- unmap_stage2_range() is a wrapper around unmap_range(), which is also used for
HYP page table setup. So unmap_range() should do the cond_resched_lock(), but
only if kvm != NULL.
- Adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
arch/arm/kvm/mmu.c | 10 ++++++++++
1 file changed, 10 insertions(+)
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -199,6 +199,12 @@ 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 the range is too large, 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);
}
@@ -553,6 +559,7 @@ 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);
}
@@ -637,7 +644,10 @@ 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_pages((unsigned long)kvm->arch.pgd, S2_PGD_ORDER);
kvm->arch.pgd = NULL;
}
Hi Ben,
There is a follow up patch for this one to make sure we check/free the PGD under the
mmu_lock.
commit 6c0d706b563af73 ("kvm: arm/arm64: Fix race in resetting stage2 PGD")
So unless you want to fold that in, this looks alright. Looks like we missed a Cc:
stable for that. I will send it to stable soon.
Cheers
Suzuki