On 6/24/2021 11:05 AM, Steven Sistare wrote: > On 6/15/2021 3:14 PM, Dr. David Alan Gilbert wrote: >> * Steven Sistare (steven.sist...@oracle.com) wrote: >>> On 5/20/2021 9:00 AM, Dr. David Alan Gilbert wrote: >>>> Hi Steven, >>>> I'd like to split the discussion into reboot and restart, >>>> so I can make sure I understand them individually. >>>> >>>> So reboot mode; >>>> Can you explain which parts of this series are needed for reboot mode; >>>> I've managed to do a kexec based reboot on qemu with the current qemu - >>>> albeit with no vfio devices, my current understanding is that for doing >>>> reboot with vfio we just need some way of getting migrate to send the >>>> metadata associated with vfio devices if the guest is in S3. >>>> >>>> Is there something I'm missing and which you have in this series? >>> >>> You are correct, this series has little special code for reboot mode, but >>> it does allow >>> reboot and restart to be handled similarly, which simplifies the management >>> layer because >>> the same calls are performed for each mode. >>> >>> For vfio in reboot mode, prior to sending cprload, the manager sends the >>> guest-suspend-ram >>> command to the qemu guest agent. This flushes requests and brings the guest >>> device to a >>> reset state, so there is no vfio metadata to save. Reboot mode does not >>> call vfio_cprsave. >>> >>> There are a few unique patches to support reboot mode. One is >>> qemu_ram_volatile, which >>> is a sanity check that the writable ram blocks are backed by some form of >>> shared memory. >>> Plus there are a few fragments in the "cpr" patch that handle the suspended >>> state that >>> is induced by guest-suspend-ram. See qemu_system_start_on_wake_request() >>> and instances >>> of RUN_STATE_SUSPENDED in migration/cpr.c >> >> Could you split the 'reboot' part of separately, then we can review >> that and perhaps get it in first? It should be a relatively small patch >> set - it'll get things moving in the right direction. >> >> The guest-suspend-ram stuff seems reasonable as an idea; lets just try >> and avoid doing it all via environment variables though; make it proper >> command line options. > > How about I delete reboot mode and the mode argument instead. Having two > modes is causing no > end of confusion, and my primary business need is for restart mode.
I just posted V4 of the patch series, refactoring reboot mode into the first 4 patches. - Steve
