[PATCH v5 10/15] KVM: Add kvm_arch_dirty_ring_size_updated() hook

[Tian Zheng]

Draining a CPU-side dirty log buffer into the dirty ring requires
sizing that buffer against the ring, which reserves room for a full
flush. Add a kvm_arch_dirty_ring_size_updated() hook called right
after kvm->dirty_ring_size is recorded, with a __weak no-op default.

arm64 will use it to pin its HDBSS buffer size in dirty-ring mode.

Signed-off-by: Tian Zheng <zhengtian10@xxxxxxxxxx>
---
 include/linux/kvm_dirty_ring.h | 1 +
 virt/kvm/dirty_ring.c          | 4 ++++
 virt/kvm/kvm_main.c            | 1 +
 3 files changed, 6 insertions(+)

diff --git a/include/linux/kvm_dirty_ring.h b/include/linux/kvm_dirty_ring.h
index eb10d87adf7d..c2b922791530 100644
--- a/include/linux/kvm_dirty_ring.h
+++ b/include/linux/kvm_dirty_ring.h
@@ -73,6 +73,7 @@ static inline void kvm_dirty_ring_free(struct kvm_dirty_ring *ring)
 #else /* CONFIG_HAVE_KVM_DIRTY_RING */

 int kvm_cpu_dirty_log_size(struct kvm *kvm);
+void kvm_arch_dirty_ring_size_updated(struct kvm *kvm);
 bool kvm_use_dirty_bitmap(struct kvm *kvm);
 bool kvm_arch_allow_write_without_running_vcpu(struct kvm *kvm);
 u32 kvm_dirty_ring_get_rsvd_entries(struct kvm *kvm);
diff --git a/virt/kvm/dirty_ring.c b/virt/kvm/dirty_ring.c
index 572b854edf74..784f53c95b54 100644
--- a/virt/kvm/dirty_ring.c
+++ b/virt/kvm/dirty_ring.c
@@ -16,6 +16,10 @@ int __weak kvm_cpu_dirty_log_size(struct kvm *kvm)
 	return 0;
 }

+void __weak kvm_arch_dirty_ring_size_updated(struct kvm *kvm)
+{
+}
+
 u32 kvm_dirty_ring_get_rsvd_entries(struct kvm *kvm)
 {
 	return KVM_DIRTY_RING_RSVD_ENTRIES + kvm_cpu_dirty_log_size(kvm);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 85f42289748d..d109062f6a1c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -5011,6 +5011,7 @@ static int kvm_vm_ioctl_enable_dirty_log_ring(struct kvm *kvm, u32 size)
 		r = -EINVAL;
 	} else {
 		kvm->dirty_ring_size = size;
+		kvm_arch_dirty_ring_size_updated(kvm);
 		r = 0;
 	}

--
2.43.0