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Subject: Re: [Xen-devel] [PATCH] Xen/pciback: Implement PCI slot or bus reset
 with 'do_flr' SysFS attribute
To:     =?UTF-8?B?UGFzaSBLw6Rya2vDpGluZW4=?= <pasik@iki.fi>
Cc:     Juergen Gross <jgross@suse.com>,
        Konrad Wilk <konrad.wilk@oracle.com>,
        linux-kernel@vger.kernel.org, Jan Beulich <JBeulich@suse.com>,
        xen-devel@lists.xenproject.org,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>
References: <20171106174842.20276-1-Govinda.Tatti@Oracle.COM>
 <5A01D3F3020000780018CE86@prv-mh.provo.novell.com>
 <8940b38d-715c-9fcb-cc74-46574d416703@oracle.com>
 <20171108173808.GH20756@reaktio.net>
From:   Govinda Tatti <govinda.tatti@oracle.com>
Organization: Oracle Corporation
Message-ID: <41dc8296-a1c6-5d1b-4282-ee7338476063@oracle.com>
Date:   Wed, 8 Nov 2017 17:26:47 -0600
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Thanks Pasi for your response. Please see below for my comments.

On 11/8/2017 11:38 AM, Pasi Kärkkäinen wrote:
> Hi,
>
> On Wed, Nov 08, 2017 at 09:44:48AM -0600, Govinda Tatti wrote:
>> Thanks Jan for your review comments. Please see below for my comments.
>>
>> On 11/7/2017 8:40 AM, Jan Beulich wrote:
>>>>>> On 06.11.17 at 18:48, <Govinda.Tatti@Oracle.COM> 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.
>>
> Hmm.. I remember some discussion from ages ago related to this.
>
> Back then it was suggested to "emulate" the flr capability (by doing slot or bus reset) for devices which don't have *native* flr available? So is this patch perhaps related to that?
I don't think so but either Konrad or someone can comment on it.
>
> If the PCI device in question has native flr capability, then native flr is used, right ?
Yes.
> I guess I should read the full patch..
Please check it and let us know your comments.

Cheers
GOVINDA

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