linux-kernel - Re: [PATCH kernel v6 18/20] vfio_pci: Allow mapping extra regions

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Date:   Wed, 19 Dec 2018 09:43:58 -0700
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Alexey Kardashevskiy <aik@...abs.ru>
Cc:     linuxppc-dev@...ts.ozlabs.org,
        David Gibson <david@...son.dropbear.id.au>,
        kvm-ppc@...r.kernel.org, Alistair Popple <alistair@...ple.id.au>,
        Reza Arbab <arbab@...ux.ibm.com>,
        Sam Bobroff <sbobroff@...ux.ibm.com>,
        Piotr Jaroszynski <pjaroszynski@...dia.com>,
        Leonardo Augusto Guimarães Garcia 
        <lagarcia@...ibm.com>, Jose Ricardo Ziviani <joserz@...ux.ibm.com>,
        Daniel Henrique Barboza <danielhb413@...il.com>,
        Paul Mackerras <paulus@...abs.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH kernel v6 18/20] vfio_pci: Allow mapping extra regions

[cc +kvm, +lkml]

Sorry, just noticed these are only visible on ppc lists or for those
directly cc'd.  vfio's official development list is the kvm list.  I'll
let spapr specific changes get away without copying this list, but
changes like this really need to be visible to everyone.  Thanks,

Alex

On Wed, 19 Dec 2018 19:52:30 +1100
Alexey Kardashevskiy <aik@...abs.ru> wrote:

> So far we only allowed mapping of MMIO BARs to the userspace. However
> there are GPUs with on-board coherent RAM accessible via side
> channels which we also want to map to the userspace. The first client
> for this is NVIDIA V100 GPU with NVLink2 direct links to a POWER9
> NPU-enabled CPU; such GPUs have 16GB RAM which is coherently mapped
> to the system address space, we are going to export these as an extra
> PCI region.
> 
> We already support extra PCI regions and this adds support for mapping
> them to the userspace.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
> Reviewed-by: David Gibson <david@...son.dropbear.id.au>
> Acked-by: Alex Williamson <alex.williamson@...hat.com>
> ---
> Changes:
> v2:
> * reverted one of mistakenly removed error checks
> ---
>  drivers/vfio/pci/vfio_pci_private.h | 3 +++
>  drivers/vfio/pci/vfio_pci.c         | 9 +++++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
> index cde3b5d..86aab05 100644
> --- a/drivers/vfio/pci/vfio_pci_private.h
> +++ b/drivers/vfio/pci/vfio_pci_private.h
> @@ -59,6 +59,9 @@ struct vfio_pci_regops {
>  		      size_t count, loff_t *ppos, bool iswrite);
>  	void	(*release)(struct vfio_pci_device *vdev,
>  			   struct vfio_pci_region *region);
> +	int	(*mmap)(struct vfio_pci_device *vdev,
> +			struct vfio_pci_region *region,
> +			struct vm_area_struct *vma);
>  };
>  
>  struct vfio_pci_region {
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index fef5002..4a6f7c0 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -1130,6 +1130,15 @@ static int vfio_pci_mmap(void *device_data, struct vm_area_struct *vma)
>  		return -EINVAL;
>  	if ((vma->vm_flags & VM_SHARED) == 0)
>  		return -EINVAL;
> +	if (index >= VFIO_PCI_NUM_REGIONS) {
> +		int regnum = index - VFIO_PCI_NUM_REGIONS;
> +		struct vfio_pci_region *region = vdev->region + regnum;
> +
> +		if (region && region->ops && region->ops->mmap &&
> +		    (region->flags & VFIO_REGION_INFO_FLAG_MMAP))
> +			return region->ops->mmap(vdev, region, vma);
> +		return -EINVAL;
> +	}
>  	if (index >= VFIO_PCI_ROM_REGION_INDEX)
>  		return -EINVAL;
>  	if (!vdev->bar_mmap_supported[index])