linux-kernel - Re: [PATCH] KVM: async_pf: drop kvm_arch_async_page

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Date:   Wed, 22 Jan 2020 02:19:30 +0000
From:   linmiaohe <linmiaohe@...wei.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
CC:     Andy Lutomirski <luto@...nel.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [PATCH] KVM: async_pf: drop kvm_arch_async_page_present wrappers

Hi:
Paolo Bonzini <pbonzini@...hat.com> wrote:
>The wrappers make it less clear that the position of the call to kvm_arch_async_page_present depends on the architecture, and that only one of the two call sites will actually be active.
>Remove them.
>
>Cc: Andy Lutomirski <luto@...nel.org>
>Cc: Christian Borntraeger <borntraeger@...ibm.com>
>Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
>---
> virt/kvm/async_pf.c | 21 ++++-----------------
> 1 file changed, 4 insertions(+), 17 deletions(-)
>
>-static inline void kvm_async_page_present_sync(struct kvm_vcpu *vcpu,
>-					       struct kvm_async_pf *work)
>-{
>-#ifdef CONFIG_KVM_ASYNC_PF_SYNC
>-	kvm_arch_async_page_present(vcpu, work);
>-#endif
>-}
>-static inline void kvm_async_page_present_async(struct kvm_vcpu *vcpu,
>-						struct kvm_async_pf *work)
>-{
>-#ifndef CONFIG_KVM_ASYNC_PF_SYNC
>-	kvm_arch_async_page_present(vcpu, work);
>-#endif
>-}
>-

Actually, these two functions took me some minutes to note the difference between them.
I thought they do the same thing and really confused me ... :)

> static struct kmem_cache *async_pf_cache;
> 
> int kvm_async_pf_init(void)
>@@ -80,7 +65,8 @@ static void async_pf_execute(struct work_struct *work)
> 	if (locked)
> 		up_read(&mm->mmap_sem);
> 
>-	kvm_async_page_present_sync(vcpu, apf);
>+	if (IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))
>+		kvm_arch_async_page_present(vcpu, apf);
> 
> 	spin_lock(&vcpu->async_pf.lock);
> 	list_add_tail(&apf->link, &vcpu->async_pf.done); @@ -157,7 +143,8 @@ void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
> 		spin_unlock(&vcpu->async_pf.lock);
> 
> 		kvm_arch_async_page_ready(vcpu, work);
>-		kvm_async_page_present_async(vcpu, work);
>+		if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC))
>+			kvm_arch_async_page_present(vcpu, work);
> 
> 		list_del(&work->queue);
> 		vcpu->async_pf.queued--;
>--
>1.8.3.1

This patch really helps. Thanks!

Reviewed-by: Miaohe Lin <linmiaohe@...wei.com>