linux-kernel - Re: [PATCH 1/1] PCI: Add hp_mmio_size and hp_mmio_pref

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Message-ID: <SL2P216MB0187E0B5D83583094065CA35806B0@SL2P216MB0187.KORP216.PROD.OUTLOOK.COM>
Date:   Wed, 23 Oct 2019 10:33:42 +0000
From:   Nicholas Johnson <nicholas.johnson-opensource@...look.com.au>
To:     "mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "corbet@....net" <corbet@....net>,
        "benh@...nel.crashing.org" <benh@...nel.crashing.org>,
        "logang@...tatee.com" <logang@...tatee.com>
Subject: Re: [PATCH 1/1] PCI: Add hp_mmio_size and hp_mmio_pref_size
 parameters

On Wed, Oct 23, 2019 at 01:03:59PM +0300, mika.westerberg@...ux.intel.com wrote:
> On Wed, Oct 23, 2019 at 09:57:17AM +0000, Nicholas Johnson wrote:
> > On Wed, Oct 23, 2019 at 12:47:43PM +0300, mika.westerberg@...ux.intel.com wrote:
> > > On Wed, Oct 23, 2019 at 08:37:48AM +0000, Nicholas Johnson wrote:
> > > >  			} else if (!strncmp(str, "hpmemsize=", 10)) {
> > > > -				pci_hotplug_mem_size = memparse(str + 10, &str);
> > > > +				pci_hotplug_mmio_size =
> > > > +					memparse(str + 10, &str);
> > > > +				pci_hotplug_mmio_pref_size =
> > > > +					memparse(str + 10, &str);
> > > 
> > > Does this actually work correctly? The first memparse(str + 10, &str)
> > > modifies str so the next call will not start from the correct position
> > > anymore.
> > I have been using this for a long time now and have not had any issues.
> > Does it modify str? I thought that was done by the loop.
> 
> If you add "hpmemsize=xxx" in the command line and print both
> pci_hotplug_mmio_size and pci_hotplug_mmio_pref_size after the
> assignment, do they have the same value? If yes, then there is no
> problem.
Looking at lib/cmdline.c line 125, it looks like there is no point in me 
testing it. It looks like you are right.

What is the better fix?

pci_hotplug_mmio_size = pci_hotplug_mmio_pref_size = memparse(str + 10, &str);

^ Could be too long, even if we are ignoring the 80-character limit.

> 
> > Can somebody else please weigh in here? I am worried now, and I want to 
> > be sure. If it is a problem, then I will have to read it into 
> > pci_hotplug_mmio_size and then set:
> > 
> > pci_hotplug_mmio_pref_size = pci_hotplug_mmio_size
> 
> Yup.
Or do you prefer the above?

Thanks