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From: | Jason Wang |
Subject: | Re: [PATCH RFC 0/1] To add HMP interface to dump PCI MSI-X table/PBA |
Date: | Wed, 28 Apr 2021 10:31:52 +0800 |
User-agent: | Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 |
在 2021/4/27 下午4:53, Dr. David Alan Gilbert 写道:
* 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.
I think we'd better have more information, e.g the device can optionally report how the MSI-X vector is used.
Virtio-pci could be the first user for this.
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.
One interesting point is that MSI could be extended for other bus, (e.g MMIO). So "info msi" should be better I guess.
Figuring out the QMP representation of your entries might be harder - and if this is strictly for debug, probably not worth it?
I think so. Thanks
DaveDongli Zhang2. 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. ThanksThank you very much! Dongli Zhang
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