linux-kernel - Re: [PATCH] powernv: fix VFIO support with PHB3

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Message-ID: <20131207115829.GA32319@oc0268524204.ibm.com>
Date:	Sat, 7 Dec 2013 09:58:29 -0200
From:	Thadeu Lima de Souza Cascardo <cascardo@...ux.vnet.ibm.com>
To:	Alexey Kardashevskiy <aik@...abs.ru>
Cc:	benh@...nel.crashing.org, linuxppc-dev@...ts.ozlabs.org,
	paulus@...ba.org, shangw@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powernv: fix VFIO support with PHB3

On Sat, Dec 07, 2013 at 11:58:44AM +1100, Alexey Kardashevskiy wrote:
> On 12/06/2013 11:21 PM, Thadeu Lima de Souza Cascardo wrote:
> > I have recently found out that no iommu_groups could be found under
> > /sys/ on a P8. That prevents PCI passthrough from working.
> > 
> > During my investigation, I found out there seems to be a missing
> > iommu_register_group for PHB3. The following patch seems to fix the
> > problem. After applying it, I see iommu_groups under
> > /sys/kernel/iommu_groups/, and can also bind vfio-pci to an adapter,
> > which gives me a device at /dev/vfio/.
> > 
> > Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@...ux.vnet.ibm.com>
> > ---
> >  arch/powerpc/platforms/powernv/pci-ioda.c |    1 +
> >  1 files changed, 1 insertions(+), 0 deletions(-)
> > 
> > diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> > index 084cdfa..2c6d173 100644
> > --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> > +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> > @@ -720,6 +720,7 @@ static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
> >  		tbl->it_type = TCE_PCI_SWINV_CREATE | TCE_PCI_SWINV_FREE;
> >  	}
> >  	iommu_init_table(tbl, phb->hose->node);
> > +	iommu_register_group(tbl, pci_domain_nr(pe->pbus), pe->pe_number);
> >  
> >  	if (pe->pdev)
> >  		set_iommu_table_base(&pe->pdev->dev, tbl);
> 
> 
> This does not seem absolutely right - normally set_iommu_table_base() is
> replaced with set_iommu_table_base_and_group() or you will not see some
> devices in a group and this may make VFIO unhappy.

Alexey,

Your patch "[PATCH v9] PPC: POWERNV: move iommu_add_device earlier" is
not upstream yet. It calls set_iommu_table_base_and_group properly.
However, without calling iommu_register_group, there is no group to add
the device to.

Compare to pnv_pci_ioda_setup_dma_pe which calls iommu_register_group
too. My patch fixes this discrepancy between IODA and IODA2.

Regards.
Cascardo.

> 
> But - if every single device gets assigned to some group, then we can push
> this to Frobisher and let people test in on power8.
> 
> 
> 
> -- 
> Alexey

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