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: g...@redhat.com
> Signed-off-by: chai wen <chaiw.f...@cn.fujitsu.com>
> ---
> 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().
> 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.
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