From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Mon, 07 Jul 2014 22:41:59 +0200 (CEST) Received: from mx1.redhat.com ([209.132.183.28]:7452 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S6860043AbaGGUl4U8isW (ORCPT ); Mon, 7 Jul 2014 22:41:56 +0200 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s67KfnWD025792 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 7 Jul 2014 16:41:50 -0400 Received: from dhcp-26-207.brq.redhat.com (vpn-57-196.rdu2.redhat.com [10.10.57.196]) by int-mx13.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id s67Kfh1a008773 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Mon, 7 Jul 2014 16:41:46 -0400 Date: Mon, 7 Jul 2014 22:42:43 +0200 From: Alexander Gordeev To: Bjorn Helgaas Cc: "linux-kernel@vger.kernel.org" , "linux-doc@vger.kernel.org" , "linux-mips@linux-mips.org" , linuxppc-dev , linux-s390@vger.kernel.org, "x86@kernel.org" , xen-devel@lists.xenproject.org, "open list:INTEL IOMMU (VT-d)" , "linux-ide@vger.kernel.org" , "linux-pci@vger.kernel.org" Subject: Re: [PATCH 1/3] PCI/MSI: Add pci_enable_msi_partial() Message-ID: <20140707204242.GA27809@dhcp-26-207.brq.redhat.com> References: <4fef62a2e647a7c38e9f2a1ea4244b3506a85e2b.1402405331.git.agordeev@redhat.com> <20140702202201.GA28852@google.com> <20140704085741.GA12247@dhcp-26-207.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.68 on 10.5.11.26 Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 41069 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: agordeev@redhat.com Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips On Mon, Jul 07, 2014 at 01:40:48PM -0600, Bjorn Helgaas wrote: > As you can tell, I'm a little skeptical about this. It's a fairly big > change, it affects the arch interface, it seems to be targeted for > only a single chipset (though it's widely used), and we already > support a standard solution (MSI-X, reducing the number of vectors > requested, or even operating with 1 vector). Bjorn, I surely understand your concerns. I am answering this "summary" question right away. Even though an extra parameter is introduced, functionally this update is rather small. It is only the new pci_enable_msi_partial() function that could exploit a custom 'nvec_mme' parameter. By contrast, existing pci_enable_msi_range() function (and therefore all device drivers) is unaffected - it just rounds up 'nvec' to the nearest power of two and continues exactly as it has been. All archs besides x86 just ignore it. And x86 change is fairly small as well - all necessary functionality is already in. Thus, at the moment it is only AHCI of concern. And no, AHCI can not do MSI-X.. Thanks! > Bjorn -- Regards, Alexander Gordeev agordeev@redhat.com