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

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Date:   Mon, 6 Mar 2023 09:57:34 -0400
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     "K V P, Satyanarayana" <satyanarayana.k.v.p@...el.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        alex.williamson@...hat.com, cohuck@...hat.com
Subject: Re: [PATCH] vfio/pci: Add DVSEC PCI Extended Config Capability to
 user visible list.

On Fri, Mar 03, 2023 at 05:54:26AM +0000, K V P, Satyanarayana wrote:
> Intel Platform Monitoring Technology (PMT) support is indicated by presence
> of an Intel defined PCIe Designated Vendor Specific Extended Capabilities
> (DVSEC) structure with a PMT specific ID.However DVSEC structures may also
> be used by Intel to indicate support for other features. The Out Of Band Management
> Services Module (OOBMSM) uses DVSEC to enumerate several features, including PMT.
> 
> The current VFIO driver does not pass DVSEC capabilities to virtual machine (VM)
> which makes intel_vsec driver not to work in the VM. This series adds DVSEC
> capability to user visible list to allow its use with VFIO.
> 
> Signed-off-by: K V P Satyanarayana <satyanarayana.k.v.p@...el.com>
> ---
>  drivers/vfio/pci/vfio_pci_config.c | 8 ++++++++
>  1 file changed, 8 insertions(+)

Wasn't the IDXD/SIOV team proposing to use the fact that DVSEC doesn't
propogate to indicate that IMS doesn't work?

Did this plan get abandoned? It seems at odds with this patch.

Why would you use a "Platform Monitoring Technology" device with VFIO
anyhow?

Honestly I'm a bit reluctant to allow arbitary config space, some of
the stuff people put there can be dangerous.

Jason