linux-kernel - Re: [PATCH v2] vfio/pci: Add DVSEC PCI Extended Config Capability to user visible list.

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Message-ID: <20230411132806.4da1c86f.alex.williamson@redhat.com>
Date:   Tue, 11 Apr 2023 13:28:06 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     "K V P, Satyanarayana" <satyanarayana.k.v.p@...el.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        cohuck@...hat.com, jgg@...pe.ca, kevin.tian@...el.com,
        michal.winiarski@...el.com, dave.jiang@...el.com,
        ashok.raj@...el.com
Subject: Re: [PATCH v2] vfio/pci: Add DVSEC PCI Extended Config Capability
 to user visible list.

On Fri, 17 Mar 2023 08:22:22 +0000
"K V P, Satyanarayana" <satyanarayana.k.v.p@...el.com> wrote:

> The Designated Vendor-Specific Extended Capability (DVSEC Capability) is an
> optional Extended Capability that is permitted to be implemented by any PCI
> Express Function. This allows PCI Express component vendors to use
> the Extended Capability mechanism to expose vendor-specific registers that can
> be present in components by a variety of vendors. A DVSEC Capability structure
> can tell vendor-specific software which features a particular component
> supports.
> 
> An example usage of DVSEC is Intel Platform Monitoring Technology (PMT) for
> enumerating and accessing hardware monitoring capabilities on a device.
> PMT encompasses three device monitoring features, Telemetry (device metrics),
> Watcher (sampling/tracing), and Crashlog. The DVSEC is used to discover these
> features and provide a BAR offset to their registers with the Intel vendor code.
> 
> The current VFIO driver does not pass DVSEC capabilities to Virtual Machine (VM)
> which makes PMT not to work inside the virtual machine. This series adds DVSEC
> capability to user visible list to allow its use with VFIO. VFIO supports
> passing of Vendor Specific Extended Capability (VSEC) and raw write access to
> device. DVSEC also passed to VM in the same way as of VSEC.
> 
> Signed-off-by: K V P Satyanarayana <satyanarayana.k.v.p@...el.com>
> 
> Changes since Version V2:
> - Added support for raw pci write for DVSEC same as VSEC.
> ---
>  drivers/vfio/pci/vfio_pci_config.c | 7 +++++++
>  1 file changed, 7 insertions(+)

Applied to vfio next branch for v6.4.  Thanks,

Alex

> 
> diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
> index 523e0144c86f..948cdd464f4e 100644
> --- a/drivers/vfio/pci/vfio_pci_config.c
> +++ b/drivers/vfio/pci/vfio_pci_config.c
> @@ -96,6 +96,7 @@ static const u16 pci_ext_cap_length[PCI_EXT_CAP_ID_MAX + 1] = {
>  	[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_DVSEC]	=	0xFF,
>  };
>  
>  /*
> @@ -1101,6 +1102,7 @@ int __init vfio_pci_init_perm_bits(void)
>  	ret |= init_pci_ext_cap_err_perm(&ecap_perms[PCI_EXT_CAP_ID_ERR]);
>  	ret |= init_pci_ext_cap_pwr_perm(&ecap_perms[PCI_EXT_CAP_ID_PWR]);
>  	ecap_perms[PCI_EXT_CAP_ID_VNDR].writefn = vfio_raw_config_write;
> +	ecap_perms[PCI_EXT_CAP_ID_DVSEC].writefn = vfio_raw_config_write;
>  
>  	if (ret)
>  		vfio_pci_uninit_perm_bits();
> @@ -1440,6 +1442,11 @@ static int vfio_ext_cap_len(struct vfio_pci_core_device *vdev, u16 ecap, u16 epo
>  			return PCI_TPH_BASE_SIZEOF + (sts * 2) + 2;
>  		}
>  		return PCI_TPH_BASE_SIZEOF;
> +	case PCI_EXT_CAP_ID_DVSEC:
> +		ret = pci_read_config_dword(pdev, epos + PCI_DVSEC_HEADER1, &dword);
> +		if (ret)
> +			return pcibios_err_to_errno(ret);
> +		return PCI_DVSEC_HEADER1_LEN(dword);
>  	default:
>  		pci_warn(pdev, "%s: unknown length for PCI ecap %#x@%#x\n",
>  			 __func__, ecap, epos);