From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933061AbdK2Q3R (ORCPT ); Wed, 29 Nov 2017 11:29:17 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:27335 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932094AbdK2Q3Q (ORCPT ); Wed, 29 Nov 2017 11:29:16 -0500 Date: Wed, 29 Nov 2017 11:29:07 -0500 From: Konrad Rzeszutek Wilk To: Jan Beulich Cc: Govinda Tatti , xen-devel@lists.xenproject.org, Boris Ostrovsky , Juergen Gross , linux-kernel@vger.kernel.org Subject: Re: [Xen-devel] [PATCH] Xen/pciback: Implement PCI slot or bus reset with 'do_flr' SysFS attribute Message-ID: <20171129162907.GO31092@char.us.oracle.com> References: <20171106174842.20276-1-Govinda.Tatti@Oracle.COM> <5A01D3F3020000780018CE86@prv-mh.provo.novell.com> <8940b38d-715c-9fcb-cc74-46574d416703@oracle.com> <5A041FB9020000780018D6E8@prv-mh.provo.novell.com> <5A1EE1D50200007800193318@prv-mh.provo.novell.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5A1EE1D50200007800193318@prv-mh.provo.novell.com> User-Agent: Mutt/1.8.3 (2017-05-23) X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 29, 2017 at 08:35:33AM -0700, Jan Beulich wrote: > >>> On 29.11.17 at 16:08, wrote: > > On 11/9/2017 2:28 AM, Jan Beulich wrote: > >>>>> On 08.11.17 at 16:44, wrote: > >>> On 11/7/2017 8:40 AM, Jan Beulich wrote: > >>>>>>> On 06.11.17 at 18:48, wrote: > >>>>> --- a/Documentation/ABI/testing/sysfs-driver-pciback > >>>>> +++ b/Documentation/ABI/testing/sysfs-driver-pciback > >>>>> @@ -11,3 +11,15 @@ Description: > >>>>> #echo 00:19.0-E0:2:FF > /sys/bus/pci/drivers/pciback/quirks > >>>>> will allow the guest to read and write to the configuration > >>>>> register 0x0E. > >>>>> + > >>>>> +What: /sys/bus/pci/drivers/pciback/do_flr > >>>>> +Date: Nov 2017 > >>>>> +KernelVersion: 4.15 > >>>>> +Contact: xen-devel@lists.xenproject.org > >>>>> +Description: > >>>>> + An option to perform a slot or bus reset when a PCI device > >>>>> + is owned by Xen PCI backend. Writing a string of DDDD:BB:DD.F > >>>>> + will cause the pciback driver to perform a slot or bus reset > >>>>> + if the device supports it. It also checks to make sure that > >>>>> + all of the devices under the bridge are owned by Xen PCI > >>>>> + backend. > >>>> Why do you name this "do_flr" when you don't even try FLR, but > >>>> go to slot or then bus reset right away. > >>> Yes, I agree but xen toolstack has already been modified to > >>> consume"do_flr" attribute. Hence, we are using the > >>> function that matches with sysfs attribute. > >> That's not a valid reason imo: Right now the driver doesn't expose > >> such an attribute, so if the tool stack was trying to use it, it would > >> not do what is intended at present anyway (i.e. the code could at > >> best be called dead). > > Sure, we can consider renaming "do_flr" attribute to "pci reset" or "bus > > reset". > > Please let me knowyour preference. > > Well, that's more a question to Konrad as the maintainer. > Personally I'd prefer just "reset", as "pci" is redundant and "bus" Can't do 'reset'. > doesn't cover the slot variant. 'bus_reset' sounds lovely? > > >> Furthermore, contrary to what you claim in > >> your reply to Pasi, I can't see where you try an actual FLR first - > >> you go straight to pci_probe_reset_{slot,bus}(). If you actually > >> tried FLR first, only falling back to the other methods as "emulation", > >> I could certainly agree with the file name chosen. > > Currently, multiple resets are being invoked (independently) in the context > > of "xl attach/detach/shutdown/reboot". > > > > - pci_reset_function_locked (invoked by pcistub_put_pci_dev()) > > This function tries various PCI reset methods including FLR. > > - pcistub_reset_dev (called by toolsstack based on "do_flr" attribute) > > While related in a certain way, I can't really see how this addresses > the comment. > > Jan > >