Re: [PATCH v10 3/4] powerpc/powernv: Override pcibios_default_alignment() to force PCI devices to be page aligned

2017-04-17 Thread Bjorn Helgaas 
On Sat, Apr 15, 2017 at 5:06 PM, Benjamin Herrenschmidt
 wrote:
> On Sat, 2017-04-15 at 11:36 -0500, Bjorn Helgaas wrote:
>> > I agree in principle. I'm surprised that PowerPC is the only one
>> > interested here though, what about other platforms who want to use
>> > KVM and PCI pass-through and use Linux to assign BARs ?
>>
>> If I understand correctly, the problem is with BARs smaller than a
>> page, and this happens more on PowerPC because larger page sizes are
>> more common there.
>
> Yes, it happens "more". That doesn't mean it doesn't happen at all on
> others :-) Anyway, I'm not objecting, just surprised.

Yeah, I agree.  Maybe the devices interesting for pass-through tend to
have BARs of least 4KB?  Those would never be a problem on x86.  But I
have absolutely no data either way.

Re: [PATCH v10 3/4] powerpc/powernv: Override pcibios_default_alignment() to force PCI devices to be page aligned

2017-04-15 Thread Benjamin Herrenschmidt 
On Sat, 2017-04-15 at 11:36 -0500, Bjorn Helgaas wrote:
> > I agree in principle. I'm surprised that PowerPC is the only one
> > interested here though, what about other platforms who want to use
> > KVM and PCI pass-through and use Linux to assign BARs ?
> 
> If I understand correctly, the problem is with BARs smaller than a
> page, and this happens more on PowerPC because larger page sizes are
> more common there.

Yes, it happens "more". That doesn't mean it doesn't happen at all on
others :-) Anyway, I'm not objecting, just surprised.

Cheers,
Ben.

Re: [PATCH v10 3/4] powerpc/powernv: Override pcibios_default_alignment() to force PCI devices to be page aligned

2017-04-15 Thread Bjorn Helgaas 
On Fri, Apr 14, 2017 at 4:52 PM, Benjamin Herrenschmidt
 wrote:
> On Fri, 2017-04-14 at 10:58 -0500, Bjorn Helgaas wrote:
>> On Mon, Apr 10, 2017 at 07:58:13PM +0800, Yongji Xie wrote:
>> > This overrides pcibios_default_alignment() to set default alignment
>> > to PAGE_SIZE for all PCI devices on PowerNV platform. Thus sub-page
>> > BARs would not share a page and could be mapped into guest when
>> > VFIO
>> > passthrough them.
>>
>> Thanks for doing this.  This looks like a reasonable strategy to me,
>> but it would be good to get a powerpc ack for it.
>
> I agree in principle. I'm surprised that PowerPC is the only one
> interested here though, what about other platforms who want to use
> KVM and PCI pass-through and use Linux to assign BARs ?

If I understand correctly, the problem is with BARs smaller than a
page, and this happens more on PowerPC because larger page sizes are
more common there.

Bjorn

Re: [PATCH v10 3/4] powerpc/powernv: Override pcibios_default_alignment() to force PCI devices to be page aligned

2017-04-14 Thread Benjamin Herrenschmidt 
On Fri, 2017-04-14 at 10:58 -0500, Bjorn Helgaas wrote:
> On Mon, Apr 10, 2017 at 07:58:13PM +0800, Yongji Xie wrote:
> > This overrides pcibios_default_alignment() to set default alignment
> > to PAGE_SIZE for all PCI devices on PowerNV platform. Thus sub-page
> > BARs would not share a page and could be mapped into guest when
> > VFIO
> > passthrough them.
> 
> Thanks for doing this.  This looks like a reasonable strategy to me,
> but it would be good to get a powerpc ack for it.

I agree in principle. I'm surprised that PowerPC is the only one
interested here though, what about other platforms who want to use
KVM and PCI pass-through and use Linux to assign BARs ?

Cheers,
Ben.

> > Signed-off-by: Yongji Xie 
> > ---
> >  arch/powerpc/include/asm/machdep.h|2 ++
> >  arch/powerpc/kernel/pci-common.c  |8 
> >  arch/powerpc/platforms/powernv/pci-ioda.c |7 +++
> >  3 files changed, 17 insertions(+)
> > 
> > diff --git a/arch/powerpc/include/asm/machdep.h
> > b/arch/powerpc/include/asm/machdep.h
> > index 5011b69..a82c192 100644
> > --- a/arch/powerpc/include/asm/machdep.h
> > +++ b/arch/powerpc/include/asm/machdep.h
> > @@ -173,6 +173,8 @@ struct machdep_calls {
> >     /* Called after scan and before resource survey */
> >     void (*pcibios_fixup_phb)(struct pci_controller *hose);
> >  
> > +   resource_size_t (*pcibios_default_alignment)(struct
> > pci_dev *);
> > +
> >  #ifdef CONFIG_PCI_IOV
> >     void (*pcibios_fixup_sriov)(struct pci_dev *pdev);
> >     resource_size_t (*pcibios_iov_resource_alignment)(struct
> > pci_dev *, int resno);
> > diff --git a/arch/powerpc/kernel/pci-common.c
> > b/arch/powerpc/kernel/pci-common.c
> > index ffda24a..ceda574 100644
> > --- a/arch/powerpc/kernel/pci-common.c
> > +++ b/arch/powerpc/kernel/pci-common.c
> > @@ -233,6 +233,14 @@ void pcibios_reset_secondary_bus(struct
> > pci_dev *dev)
> >     pci_reset_secondary_bus(dev);
> >  }
> >  
> > +resource_size_t pcibios_default_alignment(struct pci_dev *pdev)
> > +{
> > +   if (ppc_md.pcibios_default_alignment)
> > +   return ppc_md.pcibios_default_alignment(pdev);
> > +
> > +   return 0;
> > +}
> > +
> >  #ifdef CONFIG_PCI_IOV
> >  resource_size_t pcibios_iov_resource_alignment(struct pci_dev
> > *pdev, int resno)
> >  {
> > diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c
> > b/arch/powerpc/platforms/powernv/pci-ioda.c
> > index e367382..354c852 100644
> > --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> > +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> > @@ -3297,6 +3297,11 @@ static void pnv_pci_setup_bridge(struct
> > pci_bus *bus, unsigned long type)
> >     }
> >  }
> >  
> > +static resource_size_t pnv_pci_default_alignment(struct pci_dev
> > *pdev)
> > +{
> > +   return PAGE_SIZE;
> > +}
> > +
> >  #ifdef CONFIG_PCI_IOV
> >  static resource_size_t pnv_pci_iov_resource_alignment(struct
> > pci_dev *pdev,
> >       int resno)
> > @@ -3830,6 +3835,8 @@ static void __init
> > pnv_pci_init_ioda_phb(struct device_node *np,
> >     hose->controller_ops =
> > pnv_pci_ioda_controller_ops;
> >     }
> >  
> > +   ppc_md.pcibios_default_alignment =
> > pnv_pci_default_alignment;
> > +
> >  #ifdef CONFIG_PCI_IOV
> >     ppc_md.pcibios_fixup_sriov =
> > pnv_pci_ioda_fixup_iov_resources;
> >     ppc_md.pcibios_iov_resource_alignment =
> > pnv_pci_iov_resource_alignment;
> > -- 
> > 1.7.9.5
> >

Re: [PATCH v10 3/4] powerpc/powernv: Override pcibios_default_alignment() to force PCI devices to be page aligned

2017-04-14 Thread Bjorn Helgaas 
On Mon, Apr 10, 2017 at 07:58:13PM +0800, Yongji Xie wrote:
> This overrides pcibios_default_alignment() to set default alignment
> to PAGE_SIZE for all PCI devices on PowerNV platform. Thus sub-page
> BARs would not share a page and could be mapped into guest when VFIO
> passthrough them.

Thanks for doing this.  This looks like a reasonable strategy to me,
but it would be good to get a powerpc ack for it.

> Signed-off-by: Yongji Xie 
> ---
>  arch/powerpc/include/asm/machdep.h|2 ++
>  arch/powerpc/kernel/pci-common.c  |8 
>  arch/powerpc/platforms/powernv/pci-ioda.c |7 +++
>  3 files changed, 17 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/machdep.h 
> b/arch/powerpc/include/asm/machdep.h
> index 5011b69..a82c192 100644
> --- a/arch/powerpc/include/asm/machdep.h
> +++ b/arch/powerpc/include/asm/machdep.h
> @@ -173,6 +173,8 @@ struct machdep_calls {
>   /* Called after scan and before resource survey */
>   void (*pcibios_fixup_phb)(struct pci_controller *hose);
>  
> + resource_size_t (*pcibios_default_alignment)(struct pci_dev *);
> +
>  #ifdef CONFIG_PCI_IOV
>   void (*pcibios_fixup_sriov)(struct pci_dev *pdev);
>   resource_size_t (*pcibios_iov_resource_alignment)(struct pci_dev *, int 
> resno);
> diff --git a/arch/powerpc/kernel/pci-common.c 
> b/arch/powerpc/kernel/pci-common.c
> index ffda24a..ceda574 100644
> --- a/arch/powerpc/kernel/pci-common.c
> +++ b/arch/powerpc/kernel/pci-common.c
> @@ -233,6 +233,14 @@ void pcibios_reset_secondary_bus(struct pci_dev *dev)
>   pci_reset_secondary_bus(dev);
>  }
>  
> +resource_size_t pcibios_default_alignment(struct pci_dev *pdev)
> +{
> + if (ppc_md.pcibios_default_alignment)
> + return ppc_md.pcibios_default_alignment(pdev);
> +
> + return 0;
> +}
> +
>  #ifdef CONFIG_PCI_IOV
>  resource_size_t pcibios_iov_resource_alignment(struct pci_dev *pdev, int 
> resno)
>  {
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c 
> b/arch/powerpc/platforms/powernv/pci-ioda.c
> index e367382..354c852 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -3297,6 +3297,11 @@ static void pnv_pci_setup_bridge(struct pci_bus *bus, 
> unsigned long type)
>   }
>  }
>  
> +static resource_size_t pnv_pci_default_alignment(struct pci_dev *pdev)
> +{
> + return PAGE_SIZE;
> +}
> +
>  #ifdef CONFIG_PCI_IOV
>  static resource_size_t pnv_pci_iov_resource_alignment(struct pci_dev *pdev,
> int resno)
> @@ -3830,6 +3835,8 @@ static void __init pnv_pci_init_ioda_phb(struct 
> device_node *np,
>   hose->controller_ops = pnv_pci_ioda_controller_ops;
>   }
>  
> + ppc_md.pcibios_default_alignment = pnv_pci_default_alignment;
> +
>  #ifdef CONFIG_PCI_IOV
>   ppc_md.pcibios_fixup_sriov = pnv_pci_ioda_fixup_iov_resources;
>   ppc_md.pcibios_iov_resource_alignment = pnv_pci_iov_resource_alignment;
> -- 
> 1.7.9.5
>