linux-kernel - Re: [PATCHv5 7/7] pciutils: Allow 32-bit domains

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Message-ID: <20151217182600.GA29500@localhost>
Date:	Thu, 17 Dec 2015 12:26:00 -0600
From:	Bjorn Helgaas <helgaas@...nel.org>
To:	Keith Busch <keith.busch@...el.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
	linux-pci@...r.kernel.org, Jiang Liu <jiang.liu@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Dan Williams <dan.j.williams@...el.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Bryan Veal <bryan.e.veal@...el.com>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Martin Mares <mj@....cz>,
	Jon Derrick <jonathan.derrick@...el.com>
Subject: Re: [PATCHv5 7/7] pciutils: Allow 32-bit domains

On Thu, Dec 17, 2015 at 05:34:46PM +0000, Keith Busch wrote:
> On Thu, Dec 17, 2015 at 11:15:45AM -0600, Bjorn Helgaas wrote:
> > > @@ -45,7 +45,7 @@ pci_filter_parse_slot_v33(struct pci_filter *f, char *str)
> > >  	  if (str[0] && strcmp(str, "*"))
> > >  	    {
> > >  	      long int x = strtol(str, &e, 16);
> > > -	      if ((e && *e) || (x < 0 || x > 0xffff))
> > > +	      if ((e && *e) || (x < 0))
> > 
> > Just out of curiosity (I don't maintain pciutils; Martin would apply
> > this one), is there some part of the PCI or PCI firmware spec that is
> > relevant to this change?  Maybe this is connected to parsing things
> > exported by the kernel and not directly tied to PCI at the spec level.
> >
> > Whatever it is, a pointer to the producer of the information you're
> > consuming here would help us understand and review the patch.
> 
> Hi Bjorn,
> 
> This is not tied to anything defined in PCI spec. Domain numbers being
> a software construct (ACPI6, §6.5.6), we don't need to constrain the
> representation. ACPI defines 16-bit segments, and domains provided by
> this new host bridge do not define _SEG, so this series proposes domain
> numbers outside the ACPI reachable range to avoid potential clashes.
> 
> The pciutils patch just synchronizes the essential tooling software with
> the kernel software's new representation.

That's what I figured.  It'd be useful to know exactly what is on the
other end of this, e.g., a Linux /proc or /sys file or whatever it is.

Your changelog assumes a lot of implicit knowledge about Linux, VMD,
and the previous patches in this series.  But pciutils is not
Linux-specific, and it's maintained completely separately from Linux.

This patch needs to supply enough explicit context that it makes sense
all by itself, apart from the kernel series.

Bjorn
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