From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sheng Yang Subject: Re: [PATCH] msi-x: let drivers retry when not enough vectors Date: Thu, 7 May 2009 17:40:15 +0800 Message-ID: <200905071740.16190.sheng@linux.intel.com> References: <20090507082841.GA31751@redhat.com> <200905071651.24970.sheng@linux.intel.com> <20090507092731.GH8112@parisc-linux.org> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, "Michael S. Tsirkin" , jbarnes@virtuousgeek.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, Matthew Wilcox , virtualization@lists.linux-foundation.org To: Matthew Wilcox Return-path: Received: from mga12.intel.com ([143.182.124.36]:23905 "EHLO azsmga102.ch.intel.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753005AbZEGJjr (ORCPT ); Thu, 7 May 2009 05:39:47 -0400 In-Reply-To: <20090507092731.GH8112@parisc-linux.org> Content-Disposition: inline Sender: kvm-owner@vger.kernel.org List-ID: On Thursday 07 May 2009 17:27:31 Matthew Wilcox wrote: > On Thu, May 07, 2009 at 04:51:24PM +0800, Sheng Yang wrote: > > On Thursday 07 May 2009 16:28:41 Michael S. Tsirkin wrote: > > > pci_enable_msix currently returns -EINVAL if you ask > > > for more vectors than supported by the device, which would > > > typically cause fallback to regular interrupts. > > > > > > It's better to return the table size, making the driver retry > > > MSI-X with less vectors. > > > > Hi Michael > > > > I think driver should read from capability list to know how many vector > > supported by this device before enable MSI-X for device, as > > pci_msix_table_size() did... > > I think Michael's patch makes sense. It reduces the amount of work the > driver has to do without requiring any additional work in the core. I > don't see the disadvantage to it. > > Reviewed-by: Matthew Wilcox It's indeed weird. Why the semantic of pci_enable_msix can be changed to "enable msix, or tell me how many vector do you have"? You can simply call pci_msix_table_size() to get what you want, also without any more work, no? I can't understand... -- regards Yang, Sheng