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cf87ac739e
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 only cleared in
the check, done in the newly added helper kvm_dirty_ring_check_request().
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().
Link: https://lore.kernel.org/kvmarm/87lerkwtm5.wl-maz@kernel.org
Suggested-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221110104914.31280-2-gshan@redhat.com
94 lines
2.5 KiB
C
94 lines
2.5 KiB
C
#ifndef KVM_DIRTY_RING_H
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#define KVM_DIRTY_RING_H
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#include <linux/kvm.h>
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/**
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* kvm_dirty_ring: KVM internal dirty ring structure
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*
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* @dirty_index: free running counter that points to the next slot in
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* dirty_ring->dirty_gfns, where a new dirty page should go
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* @reset_index: free running counter that points to the next dirty page
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* in dirty_ring->dirty_gfns for which dirty trap needs to
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* be reenabled
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* @size: size of the compact list, dirty_ring->dirty_gfns
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* @soft_limit: when the number of dirty pages in the list reaches this
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* limit, vcpu that owns this ring should exit to userspace
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* to allow userspace to harvest all the dirty pages
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* @dirty_gfns: the array to keep the dirty gfns
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* @index: index of this dirty ring
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*/
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struct kvm_dirty_ring {
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u32 dirty_index;
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u32 reset_index;
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u32 size;
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u32 soft_limit;
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struct kvm_dirty_gfn *dirty_gfns;
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int index;
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};
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#ifndef CONFIG_HAVE_KVM_DIRTY_RING
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/*
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* If CONFIG_HAVE_HVM_DIRTY_RING not defined, kvm_dirty_ring.o should
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* not be included as well, so define these nop functions for the arch.
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*/
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static inline u32 kvm_dirty_ring_get_rsvd_entries(void)
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{
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return 0;
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}
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static inline int kvm_dirty_ring_alloc(struct kvm_dirty_ring *ring,
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int index, u32 size)
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{
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return 0;
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}
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static inline int kvm_dirty_ring_reset(struct kvm *kvm,
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struct kvm_dirty_ring *ring)
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{
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return 0;
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}
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static inline void kvm_dirty_ring_push(struct kvm_vcpu *vcpu,
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u32 slot, u64 offset)
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{
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}
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static inline struct page *kvm_dirty_ring_get_page(struct kvm_dirty_ring *ring,
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u32 offset)
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{
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return NULL;
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}
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static inline void kvm_dirty_ring_free(struct kvm_dirty_ring *ring)
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{
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}
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#else /* CONFIG_HAVE_KVM_DIRTY_RING */
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u32 kvm_dirty_ring_get_rsvd_entries(void);
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int kvm_dirty_ring_alloc(struct kvm_dirty_ring *ring, int index, u32 size);
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/*
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* called with kvm->slots_lock held, returns the number of
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* processed pages.
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*/
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int kvm_dirty_ring_reset(struct kvm *kvm, struct kvm_dirty_ring *ring);
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/*
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* returns =0: successfully pushed
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* <0: unable to push, need to wait
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*/
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void kvm_dirty_ring_push(struct kvm_vcpu *vcpu, u32 slot, u64 offset);
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bool kvm_dirty_ring_check_request(struct kvm_vcpu *vcpu);
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/* for use in vm_operations_struct */
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struct page *kvm_dirty_ring_get_page(struct kvm_dirty_ring *ring, u32 offset);
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void kvm_dirty_ring_free(struct kvm_dirty_ring *ring);
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#endif /* CONFIG_HAVE_KVM_DIRTY_RING */
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#endif /* KVM_DIRTY_RING_H */
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