On Mon, Jun 23, 2008 at 05:29:34AM +0300, Avi Kivity wrote:
> The page can't be swapped out since its reference count is elevated
> indefinitely.
AFAICT the page can be swapped out when the guest has exited to
userspace and the only reference is the qemu userspace mapping.
>> So, what do you have against this patch ?
>>
>
> We need to move away from reference counts, they make kvm brittle. The
> patch improves the current state of things (since pages are pinned
> indefinitely anyway now) but takes the wrong direction for the future.
>
> Note that kvmclock has the same issue, so we might as well share the
> solution:
>
> struct kvm_fast_guest_page {
> gfn_t gfn;
> struct page *page;
> spinlock_t lock;
> struct list_head link;
> }
>
> The mmu notifier callbacks can scan this list and null any pages that
> match the gfn being cleared, but in the normal cast, ->page can be
> accessed directly.
OK, can you please apply this at least:
KVM: move slots_lock acquision down to vapic_exit
There is no need to grab slots_lock if the vapic_page will not
be touched.
Signed-off-by: Marcelo Tosatti <[EMAIL PROTECTED]>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 26b051b..29e8983 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2759,8 +2759,10 @@ static void vapic_exit(struct kvm_vcpu *vcpu)
if (!apic || !apic->vapic_addr)
return;
+ down_read(&vcpu->kvm->slots_lock);
kvm_release_page_dirty(apic->vapic_page);
mark_page_dirty(vcpu->kvm, apic->vapic_addr >> PAGE_SHIFT);
+ up_read(&vcpu->kvm->slots_lock);
}
static int __vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
@@ -2916,9 +2918,7 @@ out:
post_kvm_run_save(vcpu, kvm_run);
- down_read(&vcpu->kvm->slots_lock);
vapic_exit(vcpu);
- up_read(&vcpu->kvm->slots_lock);
return r;
}
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