The VCPU isn't expected to be runnable when the dirty ring becomes soft
full, until the dirty pages are harvested and the dirty ring is reset
from userspace. So there is a check in each guest's entrace to see if
the dirty ring is soft full or not. The VCPU is stopped from running if
its dirty ring has been soft full. The similar check will be needed when
the feature is going to be supported on ARM64. As Marc Zyngier suggested,
a new event will avoid pointless overhead to check the size of the dirty
ring ('vcpu->kvm->dirty_ring_size') in each guest's entrance.
Add KVM_REQ_DIRTY_RING_SOFT_FULL. The event is raised when the dirty ring
becomes soft full in kvm_dirty_ring_push(). The event is cleared in the
check, done in the newly added helper kvm_dirty_ring_check_request(), or
when the dirty ring is reset by userspace. Since the VCPU is not runnable
when the dirty ring becomes soft full, the KVM_REQ_DIRTY_RING_SOFT_FULL
event is always set to prevent the VCPU from running until the dirty pages
are harvested and the dirty ring is reset by userspace.
kvm_dirty_ring_soft_full() becomes a private function with the newly added
helper kvm_dirty_ring_check_request(). The alignment for the various event
definitions in kvm_host.h is changed to tab character by the way. In order
to avoid using 'container_of()', the argument @ring is replaced by @vcpu
in kvm_dirty_ring_push() and kvm_dirty_ring_reset(). The argument @kvm to
kvm_dirty_ring_reset() is dropped since it can be retrieved from the VCPU.
Link: https://lore.kernel.org/kvmarm/87lerkwtm5.wl-maz@xxxxxxxxxx
Suggested-by: Marc Zyngier <maz@xxxxxxxxxx>
Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
---
arch/x86/kvm/x86.c | 15 ++++++---------
include/linux/kvm_dirty_ring.h | 17 ++++++-----------
include/linux/kvm_host.h | 9 +++++----
virt/kvm/dirty_ring.c | 34 +++++++++++++++++++++++++++++++---
virt/kvm/kvm_main.c | 5 ++---
5 files changed, 50 insertions(+), 30 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9cf1ba865562..d0d32e67ebf3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10499,20 +10499,17 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
bool req_immediate_exit = false;
- /* Forbid vmenter if vcpu dirty ring is soft-full */
- if (unlikely(vcpu->kvm->dirty_ring_size &&
- kvm_dirty_ring_soft_full(&vcpu->dirty_ring))) {
- vcpu->run->exit_reason = KVM_EXIT_DIRTY_RING_FULL;
- trace_kvm_dirty_ring_exit(vcpu);
- r = 0;
- goto out;
- }
-
if (kvm_request_pending(vcpu)) {
if (kvm_check_request(KVM_REQ_VM_DEAD, vcpu)) {
r = -EIO;
goto out;
}
+
+ if (kvm_dirty_ring_check_request(vcpu)) {
+ r = 0;
+ goto out;
+ }
+
if (kvm_check_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu)) {
if (unlikely(!kvm_x86_ops.nested_ops->get_nested_state_pages(vcpu))) {
r = 0;
diff --git a/include/linux/kvm_dirty_ring.h b/include/linux/kvm_dirty_ring.h
index 906f899813dc..53a36f38d15e 100644
--- a/include/linux/kvm_dirty_ring.h
+++ b/include/linux/kvm_dirty_ring.h
@@ -43,13 +43,12 @@ static inline int kvm_dirty_ring_alloc(struct kvm_dirty_ring *ring,
return 0;
}
-static inline int kvm_dirty_ring_reset(struct kvm *kvm,
- struct kvm_dirty_ring *ring)
+static inline int kvm_dirty_ring_reset(struct kvm_vcpu *vcpu)
{
return 0;
}
-static inline void kvm_dirty_ring_push(struct kvm_dirty_ring *ring,
+static inline void kvm_dirty_ring_push(struct kvm_vcpu *vcpu,
u32 slot, u64 offset)
{
}
@@ -64,11 +63,6 @@ static inline void kvm_dirty_ring_free(struct kvm_dirty_ring *ring)
{
}
-static inline bool kvm_dirty_ring_soft_full(struct kvm_dirty_ring *ring)
-{
- return true;
-}
-
#else /* CONFIG_HAVE_KVM_DIRTY_RING */
u32 kvm_dirty_ring_get_rsvd_entries(void);
@@ -78,19 +72,20 @@ int kvm_dirty_ring_alloc(struct kvm_dirty_ring *ring, int index, u32 size);
* called with kvm->slots_lock held, returns the number of
* processed pages.
*/
-int kvm_dirty_ring_reset(struct kvm *kvm, struct kvm_dirty_ring *ring);
+int kvm_dirty_ring_reset(struct kvm_vcpu *vcpu);
/*
* returns =0: successfully pushed
* <0: unable to push, need to wait
*/
-void kvm_dirty_ring_push(struct kvm_dirty_ring *ring, u32 slot, u64 offset);
+void kvm_dirty_ring_push(struct kvm_vcpu *vcpu, u32 slot, u64 offset);
+
+bool kvm_dirty_ring_check_request(struct kvm_vcpu *vcpu);
/* for use in vm_operations_struct */
struct page *kvm_dirty_ring_get_page(struct kvm_dirty_ring *ring, u32 offset);
void kvm_dirty_ring_free(struct kvm_dirty_ring *ring);
-bool kvm_dirty_ring_soft_full(struct kvm_dirty_ring *ring);
#endif /* CONFIG_HAVE_KVM_DIRTY_RING */
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 00c3448ba7f8..648d663f32c4 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -153,10 +153,11 @@ static inline bool is_error_page(struct page *page)
* Architecture-independent vcpu->requests bit members
* Bits 3-7 are reserved for more arch-independent bits.
*/
-#define KVM_REQ_TLB_FLUSH (0 | KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
-#define KVM_REQ_VM_DEAD (1 | KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
-#define KVM_REQ_UNBLOCK 2
-#define KVM_REQUEST_ARCH_BASE 8
+#define KVM_REQ_TLB_FLUSH (0 | KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
+#define KVM_REQ_VM_DEAD (1 | KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
+#define KVM_REQ_UNBLOCK 2
+#define KVM_REQ_DIRTY_RING_SOFT_FULL 3
+#define KVM_REQUEST_ARCH_BASE 8
/*
* KVM_REQ_OUTSIDE_GUEST_MODE exists is purely as way to force the vCPU to
diff --git a/virt/kvm/dirty_ring.c b/virt/kvm/dirty_ring.c
index d6fabf238032..6091e1403bc8 100644
--- a/virt/kvm/dirty_ring.c
+++ b/virt/kvm/dirty_ring.c
@@ -26,7 +26,7 @@ static u32 kvm_dirty_ring_used(struct kvm_dirty_ring *ring)
return READ_ONCE(ring->dirty_index) - READ_ONCE(ring->reset_index);
}
-bool kvm_dirty_ring_soft_full(struct kvm_dirty_ring *ring)
+static bool kvm_dirty_ring_soft_full(struct kvm_dirty_ring *ring)
{
return kvm_dirty_ring_used(ring) >= ring->soft_limit;
}
@@ -87,8 +87,10 @@ static inline bool kvm_dirty_gfn_harvested(struct kvm_dirty_gfn *gfn)
return smp_load_acquire(&gfn->flags) & KVM_DIRTY_GFN_F_RESET;
}
-int kvm_dirty_ring_reset(struct kvm *kvm, struct kvm_dirty_ring *ring)
+int kvm_dirty_ring_reset(struct kvm_vcpu *vcpu)
{
+ struct kvm *kvm = vcpu->kvm;
+ struct kvm_dirty_ring *ring = &vcpu->dirty_ring;
u32 cur_slot, next_slot;
u64 cur_offset, next_offset;
unsigned long mask;
@@ -142,13 +144,17 @@ int kvm_dirty_ring_reset(struct kvm *kvm, struct kvm_dirty_ring *ring)
kvm_reset_dirty_gfn(kvm, cur_slot, cur_offset, mask);
+ if (!kvm_dirty_ring_soft_full(ring))
+ kvm_clear_request(KVM_REQ_DIRTY_RING_SOFT_FULL, vcpu);
+
trace_kvm_dirty_ring_reset(ring);
return count;
}
-void kvm_dirty_ring_push(struct kvm_dirty_ring *ring, u32 slot, u64 offset)
+void kvm_dirty_ring_push(struct kvm_vcpu *vcpu, u32 slot, u64 offset)
{
+ struct kvm_dirty_ring *ring = &vcpu->dirty_ring;
struct kvm_dirty_gfn *entry;
/* It should never get full */
@@ -166,6 +172,28 @@ void kvm_dirty_ring_push(struct kvm_dirty_ring *ring, u32 slot, u64 offset)
kvm_dirty_gfn_set_dirtied(entry);
ring->dirty_index++;
trace_kvm_dirty_ring_push(ring, slot, offset);
+
+ if (kvm_dirty_ring_soft_full(ring))
+ kvm_make_request(KVM_REQ_DIRTY_RING_SOFT_FULL, vcpu);
+}
+
+bool kvm_dirty_ring_check_request(struct kvm_vcpu *vcpu)
+{
+ /*
+ * The VCPU isn't runnable when the dirty ring becomes soft full.
+ * The KVM_REQ_DIRTY_RING_SOFT_FULL event is always set to prevent
+ * the VCPU from running until the dirty pages are harvested and
+ * the dirty ring is reset by userspace.
+ */
+ if (kvm_check_request(KVM_REQ_DIRTY_RING_SOFT_FULL, vcpu) &&
+ kvm_dirty_ring_soft_full(&vcpu->dirty_ring)) {
+ kvm_make_request(KVM_REQ_DIRTY_RING_SOFT_FULL, vcpu);
+ vcpu->run->exit_reason = KVM_EXIT_DIRTY_RING_FULL;
+ trace_kvm_dirty_ring_exit(vcpu);
+ return true;
+ }
+
+ return false;
}
struct page *kvm_dirty_ring_get_page(struct kvm_dirty_ring *ring, u32 offset)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 1376a47fedee..30ff73931e1c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3314,8 +3314,7 @@ void mark_page_dirty_in_slot(struct kvm *kvm,
u32 slot = (memslot->as_id << 16) | memslot->id;
if (kvm->dirty_ring_size)
- kvm_dirty_ring_push(&vcpu->dirty_ring,
- slot, rel_gfn);
+ kvm_dirty_ring_push(vcpu, slot, rel_gfn);
else
set_bit_le(rel_gfn, memslot->dirty_bitmap);
}
@@ -4543,7 +4542,7 @@ static int kvm_vm_ioctl_reset_dirty_pages(struct kvm *kvm)
mutex_lock(&kvm->slots_lock);
kvm_for_each_vcpu(i, vcpu, kvm)
- cleared += kvm_dirty_ring_reset(vcpu->kvm, &vcpu->dirty_ring);
+ cleared += kvm_dirty_ring_reset(vcpu);
mutex_unlock(&kvm->slots_lock);
--
2.23.0
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