linux-kernel - Re: [PATCH 1/2] i2c: virtio: disable timeout handling

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Date:   Tue, 19 Oct 2021 20:07:48 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Vincent Whitchurch <vincent.whitchurch@...s.com>, wsa@...nel.org,
        jie.deng@...el.com, virtualization@...ts.linux-foundation.org,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...s.com
Subject: Re: [PATCH 1/2] i2c: virtio: disable timeout handling

On 19-10-21, 13:16, Greg KH wrote:
> On Tue, Oct 19, 2021 at 03:12:03PM +0530, Viresh Kumar wrote:
> > On 19-10-21, 11:36, Greg KH wrote:
> > > What is the "other side" here?  Is it something that you trust or not?
> > 
> > Other side can be a remote processor (for remoteproc over virtio or
> > something similar), or traditionally it can be host OS or host
> > firmware providing virtualisation to a Guest running Linux (this
> > driver). Or something else..
> > 
> > I would incline towards "we trust the other side" here.
> 
> That's in contradition with what other people seem to think the virtio
> drivers are for, see this crazy thread for details about that:
> 	https://lore.kernel.org/all/20211009003711.1390019-1-sathyanarayanan.kuppuswamy@linux.intel.com/
> 
> You can "trust" the hardware, but also handle things when hardware is
> broken, which is most often the case in the real world.

That's what I was worried about when I got you in, broken or hacked :)

> So why is having a timeout a problem here?  If you have an overloaded
> system, you want things to time out so that you can start to recover.
> 
> And if that hardware stops working?  Timeouts are good to have, why not
> just bump it up a bit if you are running into it in a real-world
> situation?

I think it is set to HZ currently, though I haven't tried big
transfers but I still get into some issues with Qemu based stuff.
Maybe we can bump it up to few seconds :)

-- 
viresh