Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753780AbbGXKKo (ORCPT ); Fri, 24 Jul 2015 06:10:44 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:37256 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750976AbbGXKKn (ORCPT ); Fri, 24 Jul 2015 06:10:43 -0400 X-IronPort-AV: E=Sophos;i="5.15,537,1432598400"; d="scan'208";a="287209950" Message-ID: <55B20F1F.60902@citrix.com> Date: Fri, 24 Jul 2015 11:10:39 +0100 From: David Vrabel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.7.0 MIME-Version: 1.0 To: Julien Grall , CC: , , , Boris Ostrovsky , Subject: Re: [Xen-devel] [PATCH v2 02/20] xen: Introduce a function to split a Linux page into Xen page References: <1436474552-31789-1-git-send-email-julien.grall@citrix.com> <1436474552-31789-3-git-send-email-julien.grall@citrix.com> <55B205FB.5080209@citrix.com> <55B20B56.7020605@citrix.com> In-Reply-To: <55B20B56.7020605@citrix.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1894 Lines: 56 On 24/07/15 10:54, Julien Grall wrote: > On 24/07/15 10:31, David Vrabel wrote: >> On 09/07/15 21:42, Julien Grall wrote: >>> The Xen interface is always using 4KB page. This means that a Linux page >>> may be split across multiple Xen page when the page granularity is not >>> the same. >>> >>> This helper will break down a Linux page into 4KB chunk and call the >>> helper on each of them. >> [...] >>> --- a/include/xen/page.h >>> +++ b/include/xen/page.h >>> @@ -39,4 +39,24 @@ struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS]; >>> >>> extern unsigned long xen_released_pages; >>> >>> +typedef int (*xen_pfn_fn_t)(struct page *page, unsigned long pfn, void *data); >>> + >>> +/* Break down the page in 4KB granularity and call fn foreach xen pfn */ >>> +static inline int xen_apply_to_page(struct page *page, xen_pfn_fn_t fn, >>> + void *data) >> >> I think this should be outlined (unless you have measurements that >> support making it inlined). > > I don't have any performance measurements. Although, when Linux is using > 4KB page granularity, the loop in this helper will be dropped by the > helper. The code would look like: > > unsigned long pfn = xen_page_to_pfn(page); > > ret = fn(page, fn, data); > if (ret) > return ret; > > The compiler could even inline the callback (fn). So it drops 2 > functions call. Ok, keep it inlined. >> Also perhaps make it >> >> int xen_for_each_gfn(struct page *page, >> xen_gfn_fn_t fn, void *data); > > gfn standing for Guest Frame Number right? Yes. This suggestion is just changing the name to make it more obvious what it does. David -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/