From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755427AbdK2PJH (ORCPT ); Wed, 29 Nov 2017 10:09:07 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:23708 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751997AbdK2PJF (ORCPT ); Wed, 29 Nov 2017 10:09:05 -0500 Subject: Re: [Xen-devel] [PATCH] Xen/pciback: Implement PCI slot or bus reset with 'do_flr' SysFS attribute To: Jan Beulich , Konrad Wilk Cc: Juergen Gross , xen-devel@lists.xenproject.org, Boris Ostrovsky , linux-kernel@vger.kernel.org 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> From: Govinda Tatti Organization: Oracle Corporation Message-ID: Date: Wed, 29 Nov 2017 09:08:18 -0600 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 In-Reply-To: <5A041FB9020000780018D6E8@prv-mh.provo.novell.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jan, Sorry for the late response. Please see below for my comments. 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. > 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) > And btw - I don't consider it too good an idea to post the next > version of a patch when discussion of the prior one hasn't really > settled yet. Sure, In future I will not post next version of the patch until we complete agree on all the review comment/fixes.Thanks. Cheers GOVINDA