Re: [PATCH RFC 0/1] To add HMP interface to dump PCI MSI-X table/PBA

[Dr. David Alan Gilbert]

* Dongli Zhang (dongli.zhang@oracle.com) wrote:
> 
> 
> On 4/22/21 11:01 PM, Jason Wang wrote:
> > 
> > 在 2021/4/23 下午12:47, Dongli Zhang 写道:
> >> This is inspired by the discussion with Jason on below patchset.
> >>
> >> https://urldefense.com/v3/__https://lists.gnu.org/archive/html/qemu-devel/2021-03/msg09020.html__;!!GqivPVa7Brio!KbGQZW5lq3JZ60k12NuWZ6Th1lT6AwmBTF0pBgoWUKKQ4-2UhdW57PtvXUN5XQnZ2NU$
> >>
> >> The new HMP command is introduced to dump the MSI-X table and PBA.
> >>
> >> Initially, I was going to add new option to "info pci". However, as the
> >> number of entries is not determined and the output of MSI-X table is much
> >> more similar to the output of hmp_info_tlb()/hmp_info_mem(), this patch
> >> adds interface for only HMP.
> >>
> >> The patch is tagged with RFC because I am looking for suggestions on:
> >>
> >> 1. Is it fine to add new "info msix <dev>" command?
> > 
> > 
> > I wonder the reason for not simply reusing "info pci"?
> 
> The "info pci" will show PCI data for all devices and it does not accept any
> argument to print for a specific device.
> 
> In addition, the "info pci" relies on qmp_query_pci(), where this patch will 
> not
> implement the interface for QMP considering the number of MSI-X entries is not
> determined.
> 
> Suppose we have 10 NVMe (emulated by QEMU with default number of queues), we
> will have about 600+ lines of output.

>From an HMP perspective I'm happy, so:

Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

but since I don't know much about MSI I'd like to see Jason's reply.

Adding an optional option to 'info pci' to limit to one device would be easy
though; that bit is probably easier than adding a new command.
Figuring out the QMP representation of your entries might be harder -
and if this is strictly for debug, probably not worth it?

Dave


> Dongli Zhang
> 
> > 
> > 
> >>
> >> 2. Is there any issue with output format?
> > 
> > 
> > If it's not for QMP, I guess it's not a part of ABI so it should be fine.
> > 
> > 
> >>
> >> 3. Is it fine to add only for HMP, but not QMP?
> > 
> > 
> > I think so.
> > 
> > Thanks
> > 
> > 
> >>
> >> Thank you very much!
> >>
> >> Dongli Zhang
> >>
> >>
> >>
> > 
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK