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Date: Tue, 15 Oct 2013 13:43:59 +0300
From: Gleb Natapov <gleb@...hat.com>
To: chai wen <chaiw.fnst@...fujitsu.com>
Cc: linux-kernel@...r.kernel.org, pbonzini@...hat.com,
tangchen@...fujitsu.com, guz.fnst@...fujitsu.com,
zhangyanfei@...fujitsu.com, isimatu.yasuaki@...fujitsu.com,
chaiwen_0825@...mail.com
Subject: Re: [PATCH RESEND] Drop-FOLL_GET-in-GUP-when-doing-async_pf-in-kvm
On Mon, Oct 14, 2013 at 10:22:33PM +0800, chai wen wrote:
>
> Hi Gleb
>
> I am sorry for my mistake before.
> This new patch is based on 'git://git.kernel.org/pub/scm/virt/kvm/kvm.git'.
> Page pinning is not mandatory in kvm async_pf processing and probably
> should be dropped later. And we don't mind whether the GUP is failed or
> not. What we need to do is to wake up guests process that is waitting on
> a page. So drop the FOLL_GET flag in GUP, and do some simplifying in
> async_pf check/clear processing.
> To trigger the happening of async_pf, it needs some memory stress in system
> for doing swap pressure. I simply run some big block dd processes in system
> before. And it works as I see some async_pf happening and the vm works well.
> But I do not know the exact occasion of the async_pf happening.
> Thanks.
>
Applied, thanks.
> Suggested-by: Gleb Natapov <gleb@...hat.com>
> Signed-off-by: Gu zheng <guz.fnst@...fujitsu.com>
> Signed-off-by: chai wen <chaiw.fnst@...fujitsu.com>
> ---
> arch/x86/kvm/x86.c | 4 ++--
> include/linux/kvm_host.h | 2 +-
> include/trace/events/kvm.h | 10 ++++------
> virt/kvm/async_pf.c | 17 +++++------------
> 4 files changed, 12 insertions(+), 21 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index c951c71..edf2a07 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7298,7 +7298,7 @@ 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))
> + work->wakeup_all)
> return;
>
> r = kvm_mmu_reload(vcpu);
> @@ -7408,7 +7408,7 @@ 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->wakeup_all)
> 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 7c961e1..5841e14 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 wakeup_all;
> };
>
> void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu);
> diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
> index 7005d11..131a0bd 100644
> --- a/include/trace/events/kvm.h
> +++ b/include/trace/events/kvm.h
> @@ -296,23 +296,21 @@ DEFINE_EVENT(kvm_async_pf_nopresent_ready, kvm_async_pf_ready,
>
> TRACE_EVENT(
> kvm_async_pf_completed,
> - TP_PROTO(unsigned long address, struct page *page, u64 gva),
> - TP_ARGS(address, page, gva),
> + TP_PROTO(unsigned long address, u64 gva),
> + TP_ARGS(address, gva),
>
> TP_STRUCT__entry(
> __field(unsigned long, address)
> - __field(pfn_t, pfn)
> __field(u64, gva)
> ),
>
> TP_fast_assign(
> __entry->address = address;
> - __entry->pfn = page ? page_to_pfn(page) : 0;
> __entry->gva = gva;
> ),
>
> - TP_printk("gva %#llx address %#lx pfn %#llx", __entry->gva,
> - __entry->address, __entry->pfn)
> + TP_printk("gva %#llx address %#lx", __entry->gva,
> + __entry->address)
> );
>
> #endif
> diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
> index b197950..8631d9c 100644
> --- a/virt/kvm/async_pf.c
> +++ b/virt/kvm/async_pf.c
> @@ -56,7 +56,6 @@ void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu)
>
> static void async_pf_execute(struct work_struct *work)
> {
> - struct page *page = NULL;
> struct kvm_async_pf *apf =
> container_of(work, struct kvm_async_pf, work);
> struct mm_struct *mm = apf->mm;
> @@ -68,13 +67,12 @@ 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);
> + 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;
> spin_unlock(&vcpu->async_pf.lock);
>
> /*
> @@ -82,7 +80,7 @@ static void async_pf_execute(struct work_struct *work)
> * this point
> */
>
> - trace_kvm_async_pf_completed(addr, page, gva);
> + trace_kvm_async_pf_completed(addr, gva);
>
> if (waitqueue_active(&vcpu->wq))
> wake_up_interruptible(&vcpu->wq);
> @@ -112,8 +110,6 @@ 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);
> @@ -133,14 +129,11 @@ void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
> list_del(&work->link);
> spin_unlock(&vcpu->async_pf.lock);
>
> - if (work->page)
> - kvm_arch_async_page_ready(vcpu, work);
> + 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);
> }
> }
> @@ -163,7 +156,7 @@ int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn,
> if (!work)
> return 0;
>
> - work->page = NULL;
> + work->wakeup_all = false;
> work->vcpu = vcpu;
> work->gva = gva;
> work->addr = gfn_to_hva(vcpu->kvm, gfn);
> @@ -203,7 +196,7 @@ int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
> if (!work)
> return -ENOMEM;
>
> - work->page = KVM_ERR_PTR_BAD_PAGE;
> + work->wakeup_all = true;
> INIT_LIST_HEAD(&work->queue); /* for list_del to work */
>
> spin_lock(&vcpu->async_pf.lock);
> --
> 1.7.1
--
Gleb.
--
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