linux-kernel - Re: [RFC PATCH v4 7/7] powerpc/powernv/pci-ioda: Add IOMMU_CAP_INTR

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Date:	Wed, 16 Mar 2016 10:32:07 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	Yongji Xie <xyjxie@...ux.vnet.ibm.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-doc@...r.kernel.org, bhelgaas@...gle.com, corbet@....net,
	aik@...abs.ru, benh@...nel.crashing.org, paulus@...ba.org,
	mpe@...erman.id.au, warrier@...ux.vnet.ibm.com,
	zhong@...ux.vnet.ibm.com, nikunj@...ux.vnet.ibm.com
Subject: Re: [RFC PATCH v4 7/7] powerpc/powernv/pci-ioda: Add
 IOMMU_CAP_INTR_REMAP for IODA host bridge

On Mon,  7 Mar 2016 15:48:38 +0800
Yongji Xie <xyjxie@...ux.vnet.ibm.com> wrote:

> This patch adds IOMMU_CAP_INTR_REMAP for IODA host bridge so that
> we can mmap MSI-X table in vfio driver.
> 
> Signed-off-by: Yongji Xie <xyjxie@...ux.vnet.ibm.com>
> ---
>  arch/powerpc/platforms/powernv/pci-ioda.c |   17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> index f90dc04..f01b9ab 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -1955,6 +1955,20 @@ static struct iommu_table_ops pnv_ioda2_iommu_ops = {
>  	.free = pnv_ioda2_table_free,
>  };
>  
> +static bool pnv_ioda_iommu_capable(enum iommu_cap cap)
> +{
> +	switch (cap) {
> +	case IOMMU_CAP_INTR_REMAP:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static struct iommu_ops pnv_ioda_iommu_ops = {
> +	.capable = pnv_ioda_iommu_capable,
> +};
> +
>  static void pnv_pci_ioda_setup_dma_pe(struct pnv_phb *phb,
>  				      struct pnv_ioda_pe *pe, unsigned int base,
>  				      unsigned int segs)
> @@ -3078,6 +3092,9 @@ static void pnv_pci_ioda_fixup(void)
>  
>  	/* Link NPU IODA tables to their PCI devices. */
>  	pnv_npu_ioda_fixup();
> +
> +	/* Add IOMMU_CAP_INTR_REMAP */
> +	bus_set_iommu(&pci_bus_type, &pnv_ioda_iommu_ops);
>  }
>  
>  /*


Doesn't this set you up for a world of hurt?  bus_set_iommu() calls
iommu_bus_init() which sets up notifiers, which maybe you don't care
about, but it also means that iommu_domain_alloc(&pci_bus_type) will
segfault because you're not providing a domain_alloc callback here.