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Subject: RE: [PATCH 08/11] transport-pci: Introduce virtio extended capability
> From: Michael S. Tsirkin <mst@redhat.com> > Sent: Sunday, May 21, 2023 1:58 AM > Yes but neither can it support new devices because it does not look for the new > device id. So it's fine - I was talking about new devices using extended > capability. > > We shouldn't just laser-focus on existing software and devices, there's probably > more to come. > Sure, new devices can use new capability. I will roll this as separate patch and github issue. As we discussed, legacy register access over AQ does not need this capability anyway. So not related to v2 discussion. I am in middle of splitting this as separate patch unrelated to the v2 for legacy access. > > > But that is the case with any existing software, not just seabios. > > > > New capability is in addition to the existing one. > > And code already exists to refer to the old one, so I am not seeing any gain to > create them now. > > Any new capability that one creates in the future can be in the extended area. > > Question is about MCFG in general. Is adding capability to access MCFG to > seabios for pci accesses practical? hard? > What is MCFG? > > You mentioned a perf angle that it takes half the time, but I don't > > see how as the only change between legacy and ext is: offset. > > For a variety of reasons Linux does not use memory mapped accesses for legacy > config space, it uses cf8/cfc for that. And does it use memory mapped accesses for non-legacy config space?
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