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[RFCv2,22/25] powerpc/kvm: Exclude HPT resizes when collecting the dirty log

Message ID 1457406542-6210-23-git-send-email-david@gibson.dropbear.id.au (mailing list archive)
State RFC
Headers show

Commit Message

David Gibson March 8, 2016, 3:08 a.m. UTC 
While there is an active HPT resize in progress, working out which guest
pages are dirty is rather more complicated, because depending on exactly
the phase of the resize the information could be in either the current,
tentative or previous HPT or reverse map of the guest.

To avoid this problem, for now we just exclude collecting the dirty map
while a resize is in progress, blocking the dirty map operation until the
resize is complete.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 arch/powerpc/kvm/book3s_64_mmu_hv.c | 2 ++
 1 file changed, 2 insertions(+)
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Patch

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 5b84347..c4c1814 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -1128,6 +1128,7 @@  long kvmppc_hv_get_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot,
 	unsigned long *rmapp;
 	struct kvm_vcpu *vcpu;
 
+	mutex_lock(&kvm->arch.resize_hpt_mutex); /* exclude a concurrent HPT resize */
 	preempt_disable();
 	rmapp = memslot->arch.rmap;
 	for (i = 0; i < memslot->npages; ++i) {
@@ -1152,6 +1153,7 @@  long kvmppc_hv_get_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot,
 		spin_unlock(&vcpu->arch.vpa_update_lock);
 	}
 	preempt_enable();
+	mutex_unlock(&kvm->arch.resize_hpt_mutex);
 	return 0;
 }