On 17.01.2023 22:17, Andrew Cooper wrote: > On 19/10/2022 8:40 am, Jan Beulich wrote: >> In preparation of the introduction of new vCPU operations allowing to >> register the respective areas (one of the two is x86-specific) by >> guest-physical address, add the necessary domain cleanup hooks. > > What are the two areas you're discussing here? > > I assume you mean VCPUOP_register_vcpu_time_memory_area to be the > x86-specific op, but ARM permits both VCPUOP_register_vcpu_info and > VCPUOP_register_runstate_memory_area. > > So isn't it more 2+1 rather than 1+1?
Not in my view: The vcpu_info registration is already physical address based, and there's also no new vCPU operation introduced there. >> --- >> RFC: Zapping the areas in pv_shim_shutdown() may not be strictly >> necessary: Aiui unmap_vcpu_info() is called only because the vCPU >> info area cannot be re-registered. Beyond that I guess the >> assumption is that the areas would only be re-registered as they >> were before. If that's not the case I wonder whether the guest >> handles for both areas shouldn't also be zapped. > > At this point in pv_shim_shutdown(), have already come out of suspend > (successfully) and are preparing to poke the PV guest out of suspend too. > > The PV guest needs to not have its subsequent VCPUOP_register_vcpu_info > call fail, but beyond that I can entirely believe that it was coded to > "Linux doesn't crash" rather than "what's everything we ought to reset > here" - recall that we weren't exactly flush with time when trying to > push Shim out of the door. > > Whatever does get reregstered will be reregistered at the same > position. No guest at all is going to have details like that dynamic > across migrate. I read this as "keep code as is, drop RFC remark", but that's not necessarily the only way to interpret your reply. > As a tangential observation, i see the periodic timer gets rearmed. > This is still one of the more insane default properties of a PV guest; > Linux intentionally clobbers it on boot, but I can equivalent logic to > re-clobber after resume. I guess you meant s/can/can't spot/, in which case let's Cc Linux folks for awareness. Jan
