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

Avi Kivity
2008-09-07T08:45:42Z

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