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-requ...@redhat.com" 
> <vfio-users-requ...@redhat.com> wrote:
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>   1. VFIO 128 byte TLP size? (Oliver Heid)
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> ----------------------------------------------------------------------
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> Message: 1
> Date: Fri, 9 Mar 2018 18:03:14 +0100
> From: Oliver Heid <oliver.h...@h-next.de>
> To: vfio-users@redhat.com
> Subject: [vfio-users] VFIO 128 byte TLP size?
> Message-ID: <afcc4d41-169b-994a-5b83-ed072239e...@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!
> 
> 
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> End of vfio-users Digest, Vol 32, Issue 3
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