* Peter Maydell (peter.mayd...@linaro.org) wrote: > On Tue, 6 Sept 2022 at 20:41, John Snow <js...@redhat.com> wrote: > > Hi, I suspect I have asked this before, but I didn't write it down in > > a comment, so I forget my justification... > > > > In the QMP lib, we need to set a buffering limit for how big a QMP > > message can be -- In practice, I found that the largest possible > > response was the QAPI schema reply, and I set the code to this: > > > > # Maximum allowable size of read buffer > > _limit = (64 * 1024) > > > > However, I didn't document if this was a reasonable limit or just a > > "worksforme" one. I assume that there's no hard limit for the protocol > > or the implementation thereof in QEMU. Is there any kind of value here > > that would be more sensible than another? > > > > I'm worried that if replies get bigger in the future (possibly in some > > degenerate case I am presently unaware of) that the library default > > will become nonsensical. > > There are some QMP commands which return lists of things > where we put no inherent limit on how many things there > are in the list, like qom-list-types. We'd have to be getting > a bit enthusiastic about defining types for that to get > up towards 64K's worth of response, but it's not inherently > impossible. I think using human-monitor-command to send > an 'xp' HMP command is also a way to get back an arbitrarily > large string (just ask for a lot of memory to be dumped).
We could put size limits on xp; most Humans will only dump a few kB maximum like that, any larger and you can dump to file. Dave > -- PMM > -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
