Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756466Ab3JKKJ1 (ORCPT ); Fri, 11 Oct 2013 06:09:27 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:52672 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752713Ab3JKKJ0 convert rfc822-to-8bit (ORCPT ); Fri, 11 Oct 2013 06:09:26 -0400 X-IronPort-AV: E=Sophos;i="4.93,474,1378828800"; d="scan'208";a="8724156" Message-ID: <5257CE10.9020800@cn.fujitsu.com> Date: Fri, 11 Oct 2013 18:08:16 +0800 From: chai wen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:6.0) Gecko/20110812 Thunderbird/6.0 MIME-Version: 1.0 To: Gleb Natapov CC: linux-kernel@vger.kernel.org, pbonzini@redhat.com, tangchen@cn.fujitsu.com, guz.fnst@cn.fujitsu.com, zhangyanfei@cn.fujitsu.com, guijianfeng@cn.fujitsu.com, chaiwen_0825@hotmail.com Subject: Re: [RFC][PATCH] Drop FOLL_GET in GUP when doing async_pf in kvm References: <1381411215-23830-1-git-send-email-chaiw.fnst@cn.fujitsu.com> <20131010151539.GD15954@redhat.com> In-Reply-To: <20131010151539.GD15954@redhat.com> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2013/10/11 18:07:14, Serialize by Router on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2013/10/11 18:07:14 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5907 Lines: 176 On 10/10/2013 11:15 PM, Gleb Natapov wrote: > On Thu, Oct 10, 2013 at 09:20:15PM +0800, chai wen wrote: >> Hi Gleb >> >> Thanks for you explanation about async_pf in kvm. >> Page pinning is not mandatory in kvm async_pf processing and probably should >> be dropped later.this patch drops the FOLL_GET flag when doing GUP in async_pf >> and uses a bool (marking result of GUP) to replace the *page in kvm_async_pf >> structure to simplify some following async_pf check/clear processing. > Thanks, but the patch need to be on top of > git://git.kernel.org/pub/scm/virt/kvm/kvm.git queue branch. > > Some more comment bellow. > >> Thanks. >> >> Suggested-by: gleb@redhat.com >> Signed-off-by: chai wen >> --- >> arch/x86/kvm/x86.c | 5 ++--- >> include/linux/kvm_host.h | 2 +- >> virt/kvm/async_pf.c | 16 ++++++---------- >> 3 files changed, 9 insertions(+), 14 deletions(-) >> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> index e5ca72a..0ff7d02 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -7282,8 +7282,7 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work) >> { >> int r; >> >> - if ((vcpu->arch.mmu.direct_map != work->arch.direct_map) || >> - is_error_page(work->page)) >> + if ((vcpu->arch.mmu.direct_map != work->arch.direct_map)) >> return; >> >> r = kvm_mmu_reload(vcpu); >> @@ -7393,7 +7392,7 @@ void kvm_arch_async_page_present(struct kvm_vcpu *vcpu, >> struct x86_exception fault; >> >> trace_kvm_async_pf_ready(work->arch.token, work->gva); >> - if (is_error_page(work->page)) >> + if (!work->got_page) >> work->arch.token = ~0; /* broadcast wakeup */ >> else >> kvm_del_async_pf_gfn(vcpu, work->arch.gfn); >> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h >> index 0fbbc7a..232a7d0 100644 >> --- a/include/linux/kvm_host.h >> +++ b/include/linux/kvm_host.h >> @@ -189,7 +189,7 @@ struct kvm_async_pf { >> gva_t gva; >> unsigned long addr; >> struct kvm_arch_async_pf arch; >> - struct page *page; >> + bool got_page; > I would call it wakeup_all. > >> bool done; >> }; >> >> diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c >> index 8a39dda..0cafdc7 100644 >> --- a/virt/kvm/async_pf.c >> +++ b/virt/kvm/async_pf.c >> @@ -56,7 +56,7 @@ void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu) >> >> static void async_pf_execute(struct work_struct *work) >> { >> - struct page *page = NULL; >> + long nrpages = 0; >> struct kvm_async_pf *apf = >> container_of(work, struct kvm_async_pf, work); >> struct mm_struct *mm = apf->mm; >> @@ -68,13 +68,13 @@ static void async_pf_execute(struct work_struct *work) >> >> use_mm(mm); >> down_read(&mm->mmap_sem); >> - get_user_pages(current, mm, addr, 1, 1, 0, &page, NULL); >> + nrpages = get_user_pages(current, mm, addr, 1, 1, 0, NULL, NULL); >> up_read(&mm->mmap_sem); >> unuse_mm(mm); >> >> spin_lock(&vcpu->async_pf.lock); >> list_add_tail(&apf->link, &vcpu->async_pf.done); >> - apf->page = page; >> + apf->got_page = (1==nrpages); > Space before and after ==, but this is not needed at all. It does > not matter if GUP failed or not here. We need to wake up guest process > that is waiting on a page, so just set wakeup_all to false in kvm_setup_async_pf(). Hi Gleb Thanks for you reply. It does not matter if GUP failed or not here. But in the original logic of kvm_arch_async_page_ready and kvm_arch_async_page_present, there is is_error_page checking in them. I am not sure wheher this ?logic? should be dropped. And in kvm_async_pf_wakeup_all we used a dummy bad page pointer to generate boradcast wakeup before. if wakeup_all(bool) is marking the result of gup should it be false in this function ? thanks > >> apf->done = true; >> spin_unlock(&vcpu->async_pf.lock); >> >> @@ -114,8 +114,6 @@ void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu) >> list_entry(vcpu->async_pf.done.next, >> typeof(*work), link); >> list_del(&work->link); >> - if (!is_error_page(work->page)) >> - kvm_release_page_clean(work->page); >> kmem_cache_free(async_pf_cache, work); >> } >> spin_unlock(&vcpu->async_pf.lock); >> @@ -135,14 +133,12 @@ void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu) >> list_del(&work->link); >> spin_unlock(&vcpu->async_pf.lock); >> >> - if (work->page) >> + if (work->got_page) >> kvm_arch_async_page_ready(vcpu, work); >> kvm_arch_async_page_present(vcpu, work); >> >> list_del(&work->queue); >> vcpu->async_pf.queued--; >> - if (!is_error_page(work->page)) >> - kvm_release_page_clean(work->page); >> kmem_cache_free(async_pf_cache, work); >> } >> } >> @@ -165,7 +161,7 @@ int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn, >> if (!work) >> return 0; >> >> - work->page = NULL; >> + work->got_page = false; > Sp here do: > work->wakeup_all = false; > >> work->done = false; >> work->vcpu = vcpu; >> work->gva = gva; >> @@ -206,7 +202,7 @@ int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu) >> if (!work) >> return -ENOMEM; >> >> - work->page = KVM_ERR_PTR_BAD_PAGE; >> + work->got_page = false; > And here: > work->wakeup_all = true; >> INIT_LIST_HEAD(&work->queue); /* for list_del to work */ >> >> spin_lock(&vcpu->async_pf.lock); >> -- >> 1.7.1 > -- > Gleb. > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- Regards chai wen -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/