From patchwork Fri Aug 7 16:46:48 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Julien Grall X-Patchwork-Id: 6971791 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 995C7C05AC for ; Fri, 7 Aug 2015 16:52:08 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id B9E0120635 for ; Fri, 7 Aug 2015 16:52:07 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C8A3620628 for ; Fri, 7 Aug 2015 16:52:06 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1ZNkqR-0005ju-1R; Fri, 07 Aug 2015 16:50:11 +0000 Received: from smtp02.citrix.com ([66.165.176.63]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1ZNkpC-0004at-Br for linux-arm-kernel@lists.infradead.org; Fri, 07 Aug 2015 16:48:57 +0000 X-IronPort-AV: E=Sophos;i="5.15,630,1432598400"; d="scan'208";a="292474703" From: Julien Grall To: Subject: [PATCH v3 09/20] xen/biomerge: Don't allow biovec to be merge when Linux is not using 4KB page Date: Fri, 7 Aug 2015 17:46:48 +0100 Message-ID: <1438966019-19322-10-git-send-email-julien.grall@citrix.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1438966019-19322-1-git-send-email-julien.grall@citrix.com> References: <1438966019-19322-1-git-send-email-julien.grall@citrix.com> MIME-Version: 1.0 X-DLP: MIA1 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20150807_094854_803985_38F1D177 X-CRM114-Status: GOOD ( 13.28 ) X-Spam-Score: -4.3 (----) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: ian.campbell@citrix.com, Konrad Rzeszutek Wilk , stefano.stabellini@eu.citrix.com, linux-kernel@vger.kernel.org, Julien Grall , David Vrabel , Boris Ostrovsky , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-4.3 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On ARM all dma-capable devices on a same platform may not be protected by an IOMMU. The DMA requests have to use the BFN (i.e MFN on ARM) in order to use correctly the device. While the DOM0 memory is allocated in a 1:1 fashion (PFN == MFN), grant mapping will screw this contiguous mapping. When Linux is using 64KB page granularitary, the page may be split accross multiple non-contiguous MFN (Xen is using 4KB page granularity). Therefore a DMA request will likely fail. Checking that a 64KB page is using contiguous MFN is tedious. For now, always says that biovec are not mergeable. Signed-off-by: Julien Grall Reviewed-by: Stefano Stabellini --- Cc: Konrad Rzeszutek Wilk Cc: Boris Ostrovsky Cc: David Vrabel There is some ideas to check whether two biovec could be merged (see [1]) but it's not critical and can be consider as a performance improvement. Changes in v3: - Update commit message - s/mfn/bfn/ base on the new renaming - Update TODO Changes in v2: - Remove the workaround and check if the Linux page granularity is the same as Xen or not [1] https://lkml.org/lkml/2015/7/17/418 --- drivers/xen/biomerge.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/xen/biomerge.c b/drivers/xen/biomerge.c index 8ae2fc90..4da69db 100644 --- a/drivers/xen/biomerge.c +++ b/drivers/xen/biomerge.c @@ -6,10 +6,18 @@ bool xen_biovec_phys_mergeable(const struct bio_vec *vec1, const struct bio_vec *vec2) { +#if XEN_PAGE_SIZE == PAGE_SIZE unsigned long bfn1 = pfn_to_bfn(page_to_pfn(vec1->bv_page)); unsigned long bfn2 = pfn_to_bfn(page_to_pfn(vec2->bv_page)); return __BIOVEC_PHYS_MERGEABLE(vec1, vec2) && ((bfn1 == bfn2) || ((bfn1+1) == bfn2)); +#else + /* + * XXX: Add support for merging bio_vec when using different page + * size in Xen and Linux. + */ + return 0; +#endif } EXPORT_SYMBOL(xen_biovec_phys_mergeable);