Re: [patch 02/13] KVM: MMU: switch to get_user_pages_fast

[Avi Kivity <avi@qumranet.com>]

Marcelo Tosatti wrote:
> Avoid mmap_sem / pt lock acquision if the pagetables are present. The
> improvement for hugepage backed guests is more significant, since pte
> walk + page grab for such mappings is serialized by mm->page_table_lock.
>
> CC: Andrea Arcangeli <andrea@qumranet.com>
>
>   

I'd like to apply this.  Andrea, can you verify that mmu notifiers 
interaction is okay?

>  
>  static int kvm_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
>  {
> +	struct page *page[1];
> +	unsigned long addr;
> +	int npages;
> +	gfn_t gfn = vmf->pgoff;
>  	struct kvm *kvm = vma->vm_file->private_data;
> -	struct page *page;
>  
> -	if (!kvm_is_visible_gfn(kvm, vmf->pgoff))
> +	addr = gfn_to_hva(kvm, gfn);
> +	if (kvm_is_error_hva(addr))
>  		return VM_FAULT_SIGBUS;
> -	page = gfn_to_page(kvm, vmf->pgoff);
> -	if (is_error_page(page)) {
> -		kvm_release_page_clean(page);
> +
> +	npages = get_user_pages(current, current->mm, addr, 1, 1, 0, page,
> +				NULL);
> +	if (unlikely(npages != 1))
>  		return VM_FAULT_SIGBUS;
> -	}
> -	vmf->page = page;
> +
> +	vmf->page = page[0];
>  	return 0;
>  }
>  
>   

Why this change?

-- 
error compiling committee.c: too many arguments to function