linux-kernel - Re: [Xen-devel] [PATCH] Xen/pciback: Implement PCI slot or bus reset with 'do

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Date:   Wed, 29 Nov 2017 11:25:09 -0600
From:   Govinda Tatti <govinda.tatti@...cle.com>
To:     Jan Beulich <JBeulich@...e.com>,
        Konrad Wilk <konrad.wilk@...cle.com>
Cc:     Juergen Gross <jgross@...e.com>, xen-devel@...ts.xenproject.org,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH] Xen/pciback: Implement PCI slot or bus reset
 with 'do_flr' SysFS attribute


>>> 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.
pcistub_reset_dev() just tries slot or bus reset but not FLR since it is 
being
checked and executed by pci_reset_function_locked() if supported. May be 
we can
add FLR reset code to pcistub_reset_dev() and try FLR first before 
fall-back to
slot/bus reset.

Cheers
GOVINDA