linux-kernel - RE: [1/3] powerpc/vfio: Enable on POWERNV platform

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Message-ID: <2e087e1f2aa34c0688a6c06420872d5f@BN1PR03MB266.namprd03.prod.outlook.com>
Date:	Sat, 14 Dec 2013 04:56:06 +0000
From:	"Bharat.Bhushan@...escale.com" <Bharat.Bhushan@...escale.com>
To:	Scott Wood <scottwood@...escale.com>,
	Alexey Kardashevskiy <aik@...abs.ru>
CC:	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Alex Williamson <alex.williamson@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	David Gibson <david@...son.dropbear.id.au>,
	Varun Sethi <Varun.Sethi@...escale.com>
Subject: RE: [1/3] powerpc/vfio: Enable on POWERNV platform



> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Saturday, December 14, 2013 2:33 AM
> To: Alexey Kardashevskiy
> Cc: linuxppc-dev@...ts.ozlabs.org; kvm@...r.kernel.org; linux-
> kernel@...r.kernel.org; Alex Williamson; Paul Mackerras; David Gibson; Sethi
> Varun-B16395; Bhushan Bharat-R65777
> Subject: Re: [1/3] powerpc/vfio: Enable on POWERNV platform
> 
> On Fri, 2013-12-13 at 14:02 +1100, Alexey Kardashevskiy wrote:
> > On 12/13/2013 10:35 AM, Scott Wood wrote:
> > > On Tue, May 21, 2013 at 01:33:09PM +1000, Alexey Kardashevskiy wrote:
> > >> +static int iommu_add_device(struct device *dev) {
> > >> +	struct iommu_table *tbl;
> > >> +	int ret = 0;
> > >> +
> > >> +	if (WARN_ON(dev->iommu_group)) {
> > >> +		pr_warn("iommu_tce: device %s is already in iommu group %d,
> skipping\n",
> > >> +				dev_name(dev),
> > >> +				iommu_group_id(dev->iommu_group));
> > >> +		return -EBUSY;
> > >> +	}
> > > [snip]
> > >> +static int __init tce_iommu_init(void) {
> > >> +	struct pci_dev *pdev = NULL;
> > >> +
> > >> +	BUILD_BUG_ON(PAGE_SIZE < IOMMU_PAGE_SIZE);
> > >> +
> > >> +	for_each_pci_dev(pdev)
> > >> +		iommu_add_device(&pdev->dev);
> > >> +
> > >> +	bus_register_notifier(&pci_bus_type, &tce_iommu_bus_nb);
> > >> +	return 0;
> > >> +}
> > >> +
> > >> +subsys_initcall_sync(tce_iommu_init);
> > >
> > > This is missing a check to see whether the appropriate hardware is
> > > present.  This file should also be renamed to something less
> > > generic, and depend on a kconfig symbol more specific than CONFIG_PPC64.
> > >
> > > When this is combined with CONFIG_FSL_PAMU on hardware with a PAMU,
> > > I get a bunch of those "WARN_ON(dev->iommu_group)" dumps because
> > > PAMU already got to them.  Presumably without PAMU it silently (or
> > > with just pr_debug) bails out at some other point.
> >
> >
> > I posted (yet again) yesterday "[PATCH v11] PPC: POWERNV: move
> > iommu_add_device earlier" which should fix this. And Bharat asked many
> > times for this to get accepted :)
> 
> I still get the WARN_ONs even with that patch.  You're still registering the bus
> notifier unconditionally.

I have not tried v11 but tested V9 version of that patch. And yes, in that version the bus notifier was not registered unconditionally in kernel/iommu.c .

Thanks
-Bharat

> 
> -Scott
>