Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752168AbaBQLtk (ORCPT ); Mon, 17 Feb 2014 06:49:40 -0500 Received: from smtp02.citrix.com ([66.165.176.63]:7034 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751552AbaBQLti (ORCPT ); Mon, 17 Feb 2014 06:49:38 -0500 X-IronPort-AV: E=Sophos;i="4.95,860,1384300800"; d="scan'208";a="101394258" Message-ID: <5301F74E.3070107@citrix.com> Date: Mon, 17 Feb 2014 11:49:34 +0000 From: Zoltan Kiss User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Stefano Stabellini CC: Konrad Rzeszutek Wilk , Boris Ostrovsky , David Vrabel , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , , , , =?ISO-8859-1?Q?Roger_Pau_Monn=E9?= , Jan Beulich , Ian Campbell Subject: Re: [PATCH v9] xen/grant-table: Avoid m2p_override during mapping References: <1392238453-26147-1-git-send-email-zoltan.kiss@citrix.com> In-Reply-To: Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.80.2.133] X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16/02/14 18:36, Stefano Stabellini wrote: > On Wed, 12 Feb 2014, Zoltan Kiss wrote: >> diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h >> index e0965ab..4eaeb3f 100644 >> --- a/arch/arm/include/asm/xen/page.h >> +++ b/arch/arm/include/asm/xen/page.h >> @@ -97,16 +97,15 @@ static inline pte_t *lookup_address(unsigned long address, unsigned int *level) >> return NULL; >> } >> >> -static inline int m2p_add_override(unsigned long mfn, struct page *page, >> - struct gnttab_map_grant_ref *kmap_op) >> -{ >> - return 0; >> -} >> - >> -static inline int m2p_remove_override(struct page *page, bool clear_pte) >> -{ >> - return 0; >> -} >> +extern int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops, >> + struct gnttab_map_grant_ref *kmap_ops, >> + struct page **pages, unsigned int count, >> + bool m2p_override); >> + >> +extern int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops, >> + struct gnttab_map_grant_ref *kmap_ops, >> + struct page **pages, unsigned int count, >> + bool m2p_override); > > Much much better. > The only comment I have is about this m2p_override boolean parameter. > m2p_override is now meaningless in this context, what we really want to > let the arch specific implementation know is whether the mapping is a > kernel only mapping or a userspace mapping. > Testing for kmap_ops != NULL might even be enough, but it would not > improve the interface. gntdev is the only user of this, the kmap_ops parameter there is: use_ptemod ? map->kmap_ops + offset : NULL where: use_ptemod = !xen_feature(XENFEAT_auto_translated_physmap); So I think we can't rely on kmap_ops to decide whether we should m2p_override or not. > Is it possible to realize if the mapping is a userspace mapping by > checking for GNTMAP_application_map in map_ops? > Otherwise I would keep the boolean and rename it to user_mapping. Sounds better, but as far as I see gntdev set that flag in find_grant_ptes, which is called only if (use_ptemod) { err = apply_to_page_range(vma->vm_mm, vma->vm_start, vma->vm_end - vma->vm_start, find_grant_ptes, map); So if xen_feature(XENFEAT_auto_translated_physmap), we don't have kmap_ops, and GNTMAP_application_map is not set as well, but I guess we still need m2p_override. Or not? I'm a bit confused, maybe because of Monday ... Zoli -- 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/