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SubjectRe: [PATCH] Drop FOLL_GET in GUP when doing async_pf in kvm
On 10/14/2013 05:14 PM, Gleb Natapov wrote:
> On Mon, Oct 14, 2013 at 05:06:42PM +0800, chai wen wrote:
>> Hi Gleb
>> Thanks for you comment.
>> this new patch is based on git://git.kernel.org/pub/scm/virt/kvm/kvm.git
>> queue branch.
>> 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.
>> thanks.
>>
> Have you tested it? Compiled it?
Sorry,I forget to compile and test it.
Thanks for your reminder. I will compile and test it right now and send
it out later.
>
>> Suggested-by: Gleb Natapov <gleb@redhat.com>
>> Signed-off-by: Gu zheng <guz.fnst@cn.fujitsu.com>
>> Signed-off-by: chai wen <chaiw.fnst@cn.fujitsu.com>
>> ---
>> arch/x86/kvm/x86.c | 4 ++--
>> include/linux/kvm_host.h | 2 +-
>> virt/kvm/async_pf.c | 15 ++++-----------
>> 3 files changed, 7 insertions(+), 14 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/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
>> index b197950..81a98a4 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);
>>
>> /*
>> @@ -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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--
Regards

chai wen



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