Re: [PATCH v7 13/16] vfio/pci: Expose PCIe PASID capability to guest

From: Alex Williamson <alex.williamson@redhat.com>
To: Liu Yi L <yi.l.liu@intel.com>
Cc: jean-philippe@linaro.org, kevin.tian@intel.com,
	ashok.raj@intel.com, kvm@vger.kernel.org, jasowang@redhat.com,
	stefanha@gmail.com, iommu@lists.linux-foundation.org,
	yi.y.sun@intel.com, hao.wu@intel.com, jun.j.tian@intel.com
Subject: Re: [PATCH v7 13/16] vfio/pci: Expose PCIe PASID capability to guest
Date: Fri, 11 Sep 2020 16:13:11 -0600	[thread overview]
Message-ID: <20200911161311.13999a57@w520.home> (raw)
In-Reply-To: <1599734733-6431-14-git-send-email-yi.l.liu@intel.com>

On Thu, 10 Sep 2020 03:45:30 -0700
Liu Yi L <yi.l.liu@intel.com> wrote:

> This patch exposes PCIe PASID capability to guest for assigned devices.
> Existing vfio_pci driver hides it from guest by setting the capability
> length as 0 in pci_ext_cap_length[].

This exposes the PASID capability, but it's still read-only, so this
largely just helps userspace know where to emulate the capability,
right?  Thanks,

Alex

> And this patch only exposes PASID capability for devices which has PCIe
> PASID extended struture in its configuration space. VFs will not expose
> the PASID capability as they do not implement the PASID extended structure
> in their config space. It is a TODO in future. Related discussion can be
> found in below link:
> 
> https://lore.kernel.org/kvm/20200407095801.648b1371@w520.home/
> 
> Cc: Kevin Tian <kevin.tian@intel.com>
> CC: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Cc: Alex Williamson <alex.williamson@redhat.com>
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Lu Baolu <baolu.lu@linux.intel.com>
> Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> ---
> v5 -> v6:
> *) add review-by from Eric Auger.
> 
> v1 -> v2:
> *) added in v2, but it was sent in a separate patchseries before
> ---
>  drivers/vfio/pci/vfio_pci_config.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
> index d98843f..07ff2e6 100644
> --- a/drivers/vfio/pci/vfio_pci_config.c
> +++ b/drivers/vfio/pci/vfio_pci_config.c
> @@ -95,7 +95,7 @@ static const u16 pci_ext_cap_length[PCI_EXT_CAP_ID_MAX + 1] = {
>  	[PCI_EXT_CAP_ID_LTR]	=	PCI_EXT_CAP_LTR_SIZEOF,
>  	[PCI_EXT_CAP_ID_SECPCI]	=	0,	/* not yet */
>  	[PCI_EXT_CAP_ID_PMUX]	=	0,	/* not yet */
> -	[PCI_EXT_CAP_ID_PASID]	=	0,	/* not yet */
> +	[PCI_EXT_CAP_ID_PASID]	=	PCI_EXT_CAP_PASID_SIZEOF,
>  };
>  
>  /*

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