linux-kernel - Re: [PATCH 1/5] vfio-pci: Allow PCI IDs to be specified as module options

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Message-ID: <1426104871.3643.17.camel@redhat.com>
Date:	Wed, 11 Mar 2015 14:14:31 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	kvm@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] vfio-pci: Allow PCI IDs to be specified as module
 options

On Fri, 2015-03-06 at 16:11 -0600, Bjorn Helgaas wrote:
> On Wed, Mar 04, 2015 at 01:02:43PM -0700, Alex Williamson wrote:
> > This copies the same support from pci-stub for exactly the same
> > purpose, enabling a set of PCI IDs to be automatically added to the
> > driver's dynamic ID table at module load time.  The code here is
> > pretty simple and both vfio-pci and pci-stub are fairly unique in
> > being meta drivers, capable of attaching to any device, so there's no
> > attempt made to generalize the code into pci-core.
> > 
> > Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> > ---
> >  drivers/vfio/pci/vfio_pci.c |   46 +++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 46 insertions(+)
> > 
> > diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> > index f8a1863..b3bae4c 100644
> > --- a/drivers/vfio/pci/vfio_pci.c
> > +++ b/drivers/vfio/pci/vfio_pci.c
> > @@ -32,6 +32,10 @@
> >  #define DRIVER_AUTHOR   "Alex Williamson <alex.williamson@...hat.com>"
> >  #define DRIVER_DESC     "VFIO PCI - User Level meta-driver"
> >  
> > +static char ids[1024] __initdata;
> > +module_param_string(ids, ids, sizeof(ids), 0);
> > +MODULE_PARM_DESC(ids, "Initial PCI IDs to add to the vfio driver, format is \"vendor:device[:subvendor[:subdevice[:class[:class_mask]]]]\" and multiple comma separated entries can be specified");
> > +
> >  static bool nointxmask;
> >  module_param_named(nointxmask, nointxmask, bool, S_IRUGO | S_IWUSR);
> >  MODULE_PARM_DESC(nointxmask,
> > @@ -1034,6 +1038,46 @@ static void __exit vfio_pci_cleanup(void)
> >  	vfio_pci_uninit_perm_bits();
> >  }
> >  
> > +static void __init vfio_pci_fill_ids(void)
> > +{
> > +	char *p, *id;
> > +	int rc;
> > +
> > +	/* no ids passed actually */
> > +	if (ids[0] == '\0')
> > +		return;
> > +
> > +	/* add ids specified in the module parameter */
> > +	p = ids;
> > +	while ((id = strsep(&p, ","))) {
> > +		unsigned int vendor, device, subvendor = PCI_ANY_ID,
> > +			subdevice = PCI_ANY_ID, class = 0, class_mask = 0;
> > +		int fields;
> > +
> > +		if (!strlen(id))
> > +			continue;
> > +
> > +		fields = sscanf(id, "%x:%x:%x:%x:%x:%x",
> > +				&vendor, &device, &subvendor, &subdevice,
> > +				&class, &class_mask);
> > +
> > +		if (fields < 2) {
> > +			pr_warn("vfio-pci: invalid id string \"%s\"\n", id);
> > +			continue;
> > +		}
> > +
> > +		pr_info("vfio-pci: add %04X:%04X sub=%04X:%04X cls=%08X/%08X\n",
> 
> pci_setup_device() uses "[%04x:%04x] ... class %#08x".  Maybe they should
> be the same, at least as far as using upper/lower case, spelling out
> "class", and "0x" prefix.  Maybe there's other precedent that you're
> following and pci_setup_device() is not?

Sorry for not responding to this right away.  The precedent I was
following is pci_stub_init(), but I don't know that it's any sort of
canonical reference.  PCI output in dmesg seems pretty consistent in
using lower case hex, so I agree we should make that change.  I also
note that the default value for sub IDs is PCI_ANY_ID, which ends up
getting printed as 8 characters since we don't specify the length.  I'm
also not a fan of the lack of consistency in printing the ID vs the sub
ID nor how the line wraps in dmesg w/ timestamps enabled.  What do you
think about this:

[%04hx:%04hx[%04hx:%04hx]] class %#08x/%08x

Which gives us this and doesn't wrap:

[   92.731809] vfio_pci: add [10de:11fa[ffff:ffff]] class 0x000000/00000000
[   92.738530] vfio_pci: add [10de:0e0b[ffff:ffff]] class 0x000000/00000000

I'm open to adding 0x on the class mask as well if anyone wants it.
Thanks,
Alex

> > +			vendor, device, subvendor, subdevice,
> > +			class, class_mask);
> > +
> > +		rc = pci_add_dynid(&vfio_pci_driver, vendor, device,
> > +				   subvendor, subdevice, class, class_mask, 0);
> > +		if (rc)
> > +			pr_warn("vfio-pci: failed to add dynamic id (%d)\n",
> > +				rc);
> > +	}
> > +}
> > +
> >  static int __init vfio_pci_init(void)
> >  {
> >  	int ret;
> > @@ -1053,6 +1097,8 @@ static int __init vfio_pci_init(void)
> >  	if (ret)
> >  		goto out_driver;
> >  
> > +	vfio_pci_fill_ids();
> > +
> >  	return 0;
> >  
> >  out_driver:
> > 
> > --
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