[vfio-users] vfio-users Digest, Vol 32, Issue 3

[Steve Glaser]

Max Payload Size determines both what a Function can send and what a Function accepts. As such, it is almost always set to the lowest common denominator of everything in the PCIe Hierarchy.

If there are Hot Plug slots, software might assume something about what might be added in those when determining the lowest common denominator. 

VFs don’t have their own setting. They use the PF value. The hypervisor emulates that field. 

Steveg

> On Mar 10, 2018, at 9:00 AM, "vfio-users-request at redhat.com" <vfio-users-request at redhat.com> wrote:
> 
> Send vfio-users mailing list submissions to
>    vfio-users at redhat.com
> 
> To subscribe or unsubscribe via the World Wide Web, visit
>    https://www.redhat.com/mailman/listinfo/vfio-users
> or, via email, send a message with subject or body 'help' to
>    vfio-users-request at redhat.com
> 
> You can reach the person managing the list at
>    vfio-users-owner at redhat.com
> 
> When replying, please edit your Subject line so it is more specific
> than "Re: Contents of vfio-users digest..."
> 
> 
> Today's Topics:
> 
>   1. VFIO 128 byte TLP size? (Oliver Heid)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Fri, 9 Mar 2018 18:03:14 +0100
> From: Oliver Heid <Oliver.Heid at h-next.de>
> To: vfio-users at redhat.com
> Subject: [vfio-users] VFIO 128 byte TLP size?
> Message-ID: <afcc4d41-169b-994a-5b83-ed072239ec59 at h-next.de>
> Content-Type: text/plain; charset=utf-8; format=flowed
> 
> Does VFIO somehow limit PCIe TLP size to 128 bytes on virtualized 
> devices? In our case MaxPayload = MaxReadReq = 256 bytes in PCI config, 
> and we use 4k aligned base addresses and do not cross 4k boundaries, but 
> actual package size is only 128B. Any idea how to get 256 byte TLPs?
> Thanks!
> 
> 
> 
> ------------------------------
> 
> _______________________________________________
> vfio-users mailing list
> vfio-users at redhat.com
> https://www.redhat.com/mailman/listinfo/vfio-users
> 
> 
> End of vfio-users Digest, Vol 32, Issue 3
> *****************************************

-----------------------------------------------------------------------------------
This email message is for the sole use of the intended recipient(s) and may contain
confidential information.  Any unauthorized review, use, disclosure or distribution
is prohibited.  If you are not the intended recipient, please contact the sender by
reply email and destroy all copies of the original message.
-----------------------------------------------------------------------------------