Hello, > From: lixianglai <lixiang...@loongson.cn> > Sent: Thursday, July 27, 2023 3:14 AM > To: Gavin Shan <gs...@redhat.com>; qemu-devel@nongnu.org; Salil Mehta > <salil.me...@huawei.com>; zhukeqian <zhukeqi...@huawei.com>; Bibo Mao > <maob...@loongson.cn> > Subject: Re: [PATCH 0/8] Adds CPU hot-plug support to Loongarch > > Hi Gavin and Salil, > > On 7/27/23 8:57 AM, Gavin Shan wrote: > > Hi Xianglai, > > > > On 7/20/23 17:15, xianglai li wrote: > >> Hello everyone, We refer to the implementation of ARM CPU > >> Hot-Plug to add GED-based CPU Hot-Plug support to Loongarch. > >> > >> The first 4 patches are changes to the QEMU common code, > >> including adding GED support for CPU Hot-Plug, updating > >> the ACPI table creation process, and adding > >> qdev_disconnect_gpio_out_named > >> and cpu_address_space_destroy interfaces to release resources > >> when CPU un-plug. > >> > >> The last four patches are Loongarch architecture-related, > >> and the modifications include the definition of the hook > >> function related to the CPU Hot-(UN)Plug, the allocation > >> and release of CPU resources when CPU Hot-(UN)Plug, > >> the creation process of updating the ACPI table, > >> and finally the custom switch for the CPU Hot-Plug. > >> > > > > [...] > > > > It seems the design for ARM64 hotplug has been greatly referred, but the > > authors > > are missed to be copied if you were referring to the following repository. > > There > > will be conflicts between those two patchsets as I can see and I'm not sure > > how > > it can be resolved. In theory, one patchset needs to be rebased on another > > one > > since they're sharing large amount of codes. > > > > https://github.com/salil-mehta/qemu.git > > (branch: virt-cpuhp-armv8/rfc-v1-port11052023.dev-1) > > > > I took a quick scan on this series. Loongarch doesn't have ARM64's > > constraint due > > to vGIC3 where all vCPUs's file descriptor needs to be in place. It means > > the possible > > and not yet present vCPU needs to be visible to KVM. Without this > > constraint, the > > implementation is simplified a lot. > > We have great respect and gratitude to Salil and his team for their work > and contributions to CPU HotPlug,
Many thanks! Really appreciate this. > which greatly reduced the difficulty of developing CPU HotPlug in > Loongarch. We are glad that this work is useful to other companies as well this was one of our goal. > So, We plan to rebase the next version of patch based on their code. Great. Thanks for clarifying this as accountability is important even though we are working in a collaborative environment. As such, I am planning to send the RFC V2 in 2 weeks of time and will make sure that the patches which are required by your patch-set are formed in such a way that they can be independently accepted w.r.t rest of the ARM64 architecture specific patch-set. > Hi Salil, > > I estimate that it will take quite some time for your patch series to > merge in, > > if allowed, can you merge your patch series changes to the common code > section into the community first, > > so that our code can be rebase and merged. Sure, as clarified above, something similar, will create a patch-set which will have patches which can be independently accepted/Ack'ed and consumed even before the complete patch-set. Although I think, even in current form most patches have been arranged in such a way. But I will doubly check again before I float RFC V2. > > Besides, we found the vCPU hotplug isn't working for TCG when Salil's > > series was > > tested. I'm not sure if we have same issue with this series, or TCG > > isn't a concern > > to us at all? > > At present, QEMU only supports TCG under Loongarch, > > and we test CPU HotPlug is also carried out under QEMU TCG, > > and CPU HotPlug can work normally when testing. > > Of course, we are also very happy to see you testing CPU hotplug under > Loongarch, > > which can find more problems and help us improve our patch. We know that. There are some trivial fixes we already have, I will push them as well for the completion. We were not sure if anybody needs them as usage of vCPU Hotplug under 'accel=tcg' is highly unlikely except for testing cases. Please let us know if you have any? Many thanks! Salil.
