Re: [PATCH] Drop FOLL_GET in GUP when doing async_pf in kvm

[chai wen <chaiw.fnst@cn.fujitsu.com>]

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