linux-kernel - Re: [PATCH v2] PCI: Reduce delay after FLR of Microsoft MANA devices

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Message-ID: <aDsNhVIv5xt3S7KQ@wunner.de>
Date: Sat, 31 May 2025 16:09:09 +0200
From: Lukas Wunner <lukas@...ner.de>
To: Graham Whyte <grwhyte@...ux.microsoft.com>
Cc: linux-pci@...r.kernel.org, shyamsaini@...ux.microsoft.com,
	code@...icks.com, Okaya@...nel.org, bhelgaas@...gle.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PCI: Reduce delay after FLR of Microsoft MANA devices

On Fri, May 30, 2025 at 09:26:16AM -0700, Graham Whyte wrote:
> On 5/29/2025 3:34 AM, Lukas Wunner wrote:
> > On Wed, May 28, 2025 at 06:10:47PM +0000, grwhyte@...ux.microsoft.com wrote:
> > > Add a device-specific reset for Microsoft MANA devices with the FLR
> > > delay reduced from 100ms to 10ms. While this is not compliant with the
> > > pci spec, these devices safely complete the FLR much quicker than 100ms
> > > and this can be reduced to optimize certain scenarios
> > 
> > How often do you reset these devices that 90 msec makes a difference?
> > What are these "certain scenarios"?
> 
> VF removal and rescan is the main scenario for runtime repairs and driver
> updates.
> Doing this on scale with 100ms adds up to significant time across multiple
> VFs.

Please mention this in the commit message to avoid head-scratching
by someone reading it down the road.

Thanks,

Lukas