From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefano Stabellini Subject: Re: [PATCH v2 04/20] xen/grant: Add helper gnttab_page_grant_foreign_access_ref Date: Thu, 16 Jul 2015 16:05:12 +0100 Message-ID: References: <1436474552-31789-1-git-send-email-julien.grall@citrix.com> <1436474552-31789-5-git-send-email-julien.grall@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1ZFkmA-00010y-N6 for xen-devel@lists.xenproject.org; Thu, 16 Jul 2015 15:08:42 +0000 In-Reply-To: <1436474552-31789-5-git-send-email-julien.grall@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Julien Grall Cc: ian.campbell@citrix.com, stefano.stabellini@eu.citrix.com, Julien Grall , linux-kernel@vger.kernel.org, David Vrabel , xen-devel@lists.xenproject.org, Boris Ostrovsky , linux-arm-kernel@lists.infradead.org List-Id: xen-devel@lists.xenproject.org On Thu, 9 Jul 2015, Julien Grall wrote: > Many PV drivers contain the idiom: > > pfn = page_to_mfn(...) /* Or similar */ > gnttab_grant_foreign_access_ref > > Replace it by a new helper. Note that when Linux is using a different > page granularity than Xen, the helper only gives access to the first 4KB > grant. > > This is useful where drivers are allocating a full Linux page for each > grant. > > Also include xen/interface/grant_table.h rather than xen/grant_table.h in > asm/page.h for x86 to fix a compilation issue [1]. Only the former is > useful in order to get the structure definition. > > [1] Interpendency between asm/page.h and xen/grant_table.h which result > to page_mfn not being defined when necessary. > > Signed-off-by: Julien Grall > Cc: Konrad Rzeszutek Wilk > Cc: Boris Ostrovsky > Cc: David Vrabel > --- > Changes in v2: > - Patch added > --- > arch/x86/include/asm/xen/page.h | 2 +- > include/xen/grant_table.h | 9 +++++++++ > 2 files changed, 10 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h > index c44a5d5..fb2e037 100644 > --- a/arch/x86/include/asm/xen/page.h > +++ b/arch/x86/include/asm/xen/page.h > @@ -12,7 +12,7 @@ > #include > > #include > -#include > +#include > #include > > /* Xen machine address */ > diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h > index 6f77378..6a1ef86 100644 > --- a/include/xen/grant_table.h > +++ b/include/xen/grant_table.h > @@ -131,6 +131,15 @@ void gnttab_cancel_free_callback(struct gnttab_free_callback *callback); > void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid, > unsigned long frame, int readonly); > > +/* Give access to the first 4K of the page */ > +static inline void gnttab_page_grant_foreign_access_ref( > + grant_ref_t ref, domid_t domid, > + struct page *page, int readonly) > +{ I like this. I think it might make sense to call it gnttab_page_grant_foreign_access_ref_one to make clear that it is only granting the first 4K. In the future we could introduce a new function, called gnttab_page_grant_foreign_access_ref, that grants all 4K in the page. In any case Reviewed-by: Stefano Stabellini > + gnttab_grant_foreign_access_ref(ref, domid, page_to_mfn(page), > + readonly); > +} > + > void gnttab_grant_foreign_transfer_ref(grant_ref_t, domid_t domid, > unsigned long pfn); > > -- > 2.1.4 >