Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756084AbaAJNQ3 (ORCPT ); Fri, 10 Jan 2014 08:16:29 -0500 Received: from smtp.citrix.com ([66.165.176.89]:56972 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753269AbaAJNQ1 (ORCPT ); Fri, 10 Jan 2014 08:16:27 -0500 X-IronPort-AV: E=Sophos;i="4.95,638,1384300800"; d="scan'208";a="91660148" Date: Fri, 10 Jan 2014 13:16:25 +0000 From: Wei Liu To: Zoltan Kiss CC: Wei Liu , , , , , Subject: Re: [PATCH net-next v3 2/9] xen-netback: Change TX path from grant copy to mapping Message-ID: <20140110131625.GJ29180@zion.uk.xensource.com> References: <1389139818-24458-1-git-send-email-zoltan.kiss@citrix.com> <1389139818-24458-3-git-send-email-zoltan.kiss@citrix.com> <20140109153015.GF12164@zion.uk.xensource.com> <52CFDAEC.5080708@citrix.com> <20140110114534.GE29180@zion.uk.xensource.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20140110114534.GE29180@zion.uk.xensource.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 10, 2014 at 11:45:34AM +0000, Wei Liu wrote: > On Fri, Jan 10, 2014 at 11:35:08AM +0000, Zoltan Kiss wrote: > [...] > > > > >>@@ -920,6 +852,18 @@ static int xenvif_tx_check_gop(struct xenvif *vif, > > >> err = gop->status; > > >> if (unlikely(err)) > > >> xenvif_idx_release(vif, pending_idx, XEN_NETIF_RSP_ERROR); > > >>+ else { > > >>+ if (vif->grant_tx_handle[pending_idx] != > > >>+ NETBACK_INVALID_HANDLE) { > > >>+ netdev_err(vif->dev, > > >>+ "Stale mapped handle! pending_idx %x handle %x\n", > > >>+ pending_idx, vif->grant_tx_handle[pending_idx]); > > >>+ BUG(); > > >>+ } > > >>+ set_phys_to_machine(idx_to_pfn(vif, pending_idx), > > >>+ FOREIGN_FRAME(gop->dev_bus_addr >> PAGE_SHIFT)); > > > > > >What happens when you don't have this? > > Your frags will be filled with garbage. I don't understand exactly > > what this function does, someone might want to enlighten us? I've > > took it's usage from classic kernel. > > Also, it might be worthwhile to check the return value and BUG if > > it's false, but I don't know what exactly that return value means. > > > > This is actually part of gnttab_map_refs. As you're using hypercall > directly this becomes very fragile. > To make it clear, set_phys_to_machine is done within m2p_add_override. Wei. -- 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/