From: Bjorn Helgaas <helgaas@kernel.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: linux-pci@vger.kernel.org, Alex Williamson <alex.williamson@redhat.com>
Subject: Re: reprobing BAR sizes and capabilities after a FLR?
Date: Wed, 10 Jul 2019 09:14:38 -0500 [thread overview]
Message-ID: <20190710141438.GO128603@google.com> (raw)
In-Reply-To: <20190709154019.GA30673@infradead.org>
[+cc Alex]
On Tue, Jul 09, 2019 at 08:40:19AM -0700, Christoph Hellwig wrote:
> Hi all,
>
> I've just been talking to some firmware developers that were a little
> surprised that Linux does not reprobe BAR sizes after a FLR. I looked
> at our code and we do not reprobe anything at all after a FLR. Is it
> a good assumption that a devices comes back in exactly the same state
> after an FLR?
I am a little nervous about the fact that we don't reprobe devices
after reset because the reset may cause the device to load new
firmware, which may cause arbitrary changes (device type, number and
size of BARs, etc). FLR is a little more restrictive than
Conventional Reset, e.g., FLR must not affect the link state, so maybe
it's safer to assume BAR sizes are unchanged. But I'm not at all
confident about that.
I mooted the idea of reprobing after reset, but that would break higher
level software that isn't prepared to see hotplug-like events caused by
reset, so haven't gone that direction (yet).
Bjorn
prev parent reply other threads:[~2019-07-10 14:14 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-09 15:40 reprobing BAR sizes and capabilities after a FLR? Christoph Hellwig
2019-07-09 16:27 ` Sinan Kaya
2019-07-10 14:14 ` Bjorn Helgaas [this message]
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