Re: [PATCH v7 03/17] Xen: xlate: Use page_to_xen_pfn instead of page_to_pfn

Julien Grall
2016-03-29T16:29:02Z

Hi Shannon,

On 24/03/16 14:44, Shannon Zhao wrote:
> Make xen_xlate_map_ballooned_pages work with 64K pages. In that case
> Kernel pages are 64K in size but Xen pages remain 4K in size. Xen pfns
> refer to 4K pages.
>
> Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
> Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> ---
> drivers/xen/xlate_mmu.c | 26 ++++++++++++++++----------
> 1 file changed, 16 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/xen/xlate_mmu.c b/drivers/xen/xlate_mmu.c
> index 9692656..28f728b 100644
> --- a/drivers/xen/xlate_mmu.c
> +++ b/drivers/xen/xlate_mmu.c
> @@ -207,9 +207,12 @@ int __init xen_xlate_map_ballooned_pages(xen_pfn_t **gfns, void **virt,
> void *vaddr;
> int rc;
> unsigned int i;
> + unsigned long nr_pages;
> + xen_pfn_t xen_pfn = 0;
>
> BUG_ON(nr_grant_frames == 0);
> - pages = kcalloc(nr_grant_frames, sizeof(pages[0]), GFP_KERNEL);
> + nr_pages = DIV_ROUND_UP(nr_grant_frames, XEN_PFN_PER_PAGE);
> + pages = kcalloc(nr_pages, sizeof(pages[0]), GFP_KERNEL);
> if (!pages)
> return -ENOMEM;
>
> @@ -218,22 +221,25 @@ int __init xen_xlate_map_ballooned_pages(xen_pfn_t **gfns, void **virt,
> kfree(pages);
> return -ENOMEM;
> }
> - rc = alloc_xenballooned_pages(nr_grant_frames, pages);
> + rc = alloc_xenballooned_pages(nr_pages, pages);
> if (rc) {
> - pr_warn("%s Couldn't balloon alloc %ld pfns rc:%d\n", __func__,
> - nr_grant_frames, rc);
> + pr_warn("%s Couldn't balloon alloc %ld pages rc:%d\n", __func__,
> + nr_pages, rc);
> kfree(pages);
> kfree(pfns);
> return rc;
> }
> - for (i = 0; i < nr_grant_frames; i++)
> - pfns[i] = page_to_pfn(pages[i]);
> + for (i = 0; i < nr_grant_frames; i++) {
> + if ((i % XEN_PFN_PER_PAGE) == 0)
> + xen_pfn = page_to_xen_pfn(pages[i / XEN_PFN_PER_PAGE]);
> + pfns[i] = pfn_to_gfn(xen_pfn++);
> + }

Would it be possible to re-use xen_for_each_gfn? This will avoid
open-coding the loop to break down the Linux page.

Regards,

--
Julien Grall