| Message ID | 20240405034056.23933-1-wei.w.wang@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] migration/postcopy: ensure preempt channel is ready before loading states | expand |
On Friday, April 5, 2024 11:41 AM, Wang, Wei W wrote: > > Before loading the guest states, ensure that the preempt channel has been > ready to use, as some of the states (e.g. via virtio_load) might trigger page > faults that will be handled through the preempt channel. So yield to the main > thread in the case that the channel create event hasn't been dispatched. > > Originally-by: Lei Wang <lei4.wang@intel.com> > Link: https://lore.kernel.org/all/9aa5d1be-7801-40dd-83fd- > f7e041ced249@intel.com/T/ > Suggested-by: Peter Xu <peterx@redhat.com> > Signed-off-by: Lei Wang <lei4.wang@intel.com> > Signed-off-by: Wei Wang <wei.w.wang@intel.com> > --- > migration/savevm.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/migration/savevm.c b/migration/savevm.c index > 388d7af7cd..63f9991a8a 100644 > --- a/migration/savevm.c > +++ b/migration/savevm.c > @@ -2342,6 +2342,23 @@ static int > loadvm_handle_cmd_packaged(MigrationIncomingState *mis) > > QEMUFile *packf = qemu_file_new_input(QIO_CHANNEL(bioc)); > > + /* > + * Before loading the guest states, ensure that the preempt channel has > + * been ready to use, as some of the states (e.g. via virtio_load) might > + * trigger page faults that will be handled through the preempt channel. > + * So yield to the main thread in the case that the channel create event > + * hasn't been dispatched. > + */ > + do { > + if (!migrate_postcopy_preempt() || !qemu_in_coroutine() || > + mis->postcopy_qemufile_dst) { > + break; > + } > + > + aio_co_schedule(qemu_get_current_aio_context(), > qemu_coroutine_self()); > + qemu_coroutine_yield(); > + } while (1); > + > ret = qemu_loadvm_state_main(packf, mis); > trace_loadvm_handle_cmd_packaged_main(ret); > qemu_fclose(packf); > -- > 2.27.0 Main change from v1 is the drop of the wait on sem. It's still patched to loadvm_handle_cmd_packaged, as the sem issue (possible twice wait) isn't there now.
On Fri, Apr 05, 2024 at 11:40:56AM +0800, Wei Wang wrote: > Before loading the guest states, ensure that the preempt channel has been > ready to use, as some of the states (e.g. via virtio_load) might trigger > page faults that will be handled through the preempt channel. So yield to > the main thread in the case that the channel create event hasn't been > dispatched. > > Originally-by: Lei Wang <lei4.wang@intel.com> > Link: https://lore.kernel.org/all/9aa5d1be-7801-40dd-83fd-f7e041ced249@intel.com/T/ > Suggested-by: Peter Xu <peterx@redhat.com> The current version doesn't have any of my credits. :) Thanks, but I'll just drop it to reflect reality, so we keep the credit to the right ones. > Signed-off-by: Lei Wang <lei4.wang@intel.com> > Signed-off-by: Wei Wang <wei.w.wang@intel.com> > --- > migration/savevm.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/migration/savevm.c b/migration/savevm.c > index 388d7af7cd..63f9991a8a 100644 > --- a/migration/savevm.c > +++ b/migration/savevm.c > @@ -2342,6 +2342,23 @@ static int loadvm_handle_cmd_packaged(MigrationIncomingState *mis) > > QEMUFile *packf = qemu_file_new_input(QIO_CHANNEL(bioc)); > > + /* > + * Before loading the guest states, ensure that the preempt channel has > + * been ready to use, as some of the states (e.g. via virtio_load) might > + * trigger page faults that will be handled through the preempt channel. > + * So yield to the main thread in the case that the channel create event > + * hasn't been dispatched. I'll squash below into it. If any of you disagree please shoot: valid until this Sunday. + * TODO: if we can move migration loadvm out of main thread, then we + * won't block main thread from polling the accept() fds. We can drop + * this as a whole when that is done. Huge thanks to both! > + */ > + do { > + if (!migrate_postcopy_preempt() || !qemu_in_coroutine() || > + mis->postcopy_qemufile_dst) { > + break; > + } > + > + aio_co_schedule(qemu_get_current_aio_context(), qemu_coroutine_self()); > + qemu_coroutine_yield(); > + } while (1); > + > ret = qemu_loadvm_state_main(packf, mis); > trace_loadvm_handle_cmd_packaged_main(ret); > qemu_fclose(packf); > -- > 2.27.0 >
On Saturday, April 6, 2024 5:53 AM, Peter Xu wrote: > On Fri, Apr 05, 2024 at 11:40:56AM +0800, Wei Wang wrote: > > Before loading the guest states, ensure that the preempt channel has > > been ready to use, as some of the states (e.g. via virtio_load) might > > trigger page faults that will be handled through the preempt channel. > > So yield to the main thread in the case that the channel create event > > hasn't been dispatched. > > > > Originally-by: Lei Wang <lei4.wang@intel.com> > > Link: > > https://lore.kernel.org/all/9aa5d1be-7801-40dd-83fd-f7e041ced249@intel > > .com/T/ > > Suggested-by: Peter Xu <peterx@redhat.com> > > The current version doesn't have any of my credits. :) Thanks, but I'll just drop > it to reflect reality, so we keep the credit to the right ones. > > > Signed-off-by: Lei Wang <lei4.wang@intel.com> > > Signed-off-by: Wei Wang <wei.w.wang@intel.com> > > --- > > migration/savevm.c | 17 +++++++++++++++++ > > 1 file changed, 17 insertions(+) > > > > diff --git a/migration/savevm.c b/migration/savevm.c index > > 388d7af7cd..63f9991a8a 100644 > > --- a/migration/savevm.c > > +++ b/migration/savevm.c > > @@ -2342,6 +2342,23 @@ static int > > loadvm_handle_cmd_packaged(MigrationIncomingState *mis) > > > > QEMUFile *packf = qemu_file_new_input(QIO_CHANNEL(bioc)); > > > > + /* > > + * Before loading the guest states, ensure that the preempt channel has > > + * been ready to use, as some of the states (e.g. via virtio_load) might > > + * trigger page faults that will be handled through the preempt channel. > > + * So yield to the main thread in the case that the channel create event > > + * hasn't been dispatched. > > I'll squash below into it. If any of you disagree please shoot: valid until this > Sunday. > > + * TODO: if we can move migration loadvm out of main thread, then we > + * won't block main thread from polling the accept() fds. We can drop > + * this as a whole when that is done. > Looks good to me.
On 4/6/2024 5:53, Peter Xu wrote:> On Fri, Apr 05, 2024 at 11:40:56AM +0800, Wei Wang wrote: >> Before loading the guest states, ensure that the preempt channel has been >> ready to use, as some of the states (e.g. via virtio_load) might trigger >> page faults that will be handled through the preempt channel. So yield to >> the main thread in the case that the channel create event hasn't been >> dispatched. >> >> Originally-by: Lei Wang <lei4.wang@intel.com> >> Link: https://lore.kernel.org/all/9aa5d1be-7801-40dd-83fd-f7e041ced249@intel.com/T/ >> Suggested-by: Peter Xu <peterx@redhat.com> > > The current version doesn't have any of my credits. :) Thanks, but I'll > just drop it to reflect reality, so we keep the credit to the right ones. > >> Signed-off-by: Lei Wang <lei4.wang@intel.com> >> Signed-off-by: Wei Wang <wei.w.wang@intel.com> >> --- >> migration/savevm.c | 17 +++++++++++++++++ >> 1 file changed, 17 insertions(+) >> >> diff --git a/migration/savevm.c b/migration/savevm.c >> index 388d7af7cd..63f9991a8a 100644 >> --- a/migration/savevm.c >> +++ b/migration/savevm.c >> @@ -2342,6 +2342,23 @@ static int loadvm_handle_cmd_packaged(MigrationIncomingState *mis) >> >> QEMUFile *packf = qemu_file_new_input(QIO_CHANNEL(bioc)); >> >> + /* >> + * Before loading the guest states, ensure that the preempt channel has >> + * been ready to use, as some of the states (e.g. via virtio_load) might >> + * trigger page faults that will be handled through the preempt channel. >> + * So yield to the main thread in the case that the channel create event >> + * hasn't been dispatched. > > I'll squash below into it. If any of you disagree please shoot: valid > until this Sunday. I'm OK with it. > > + * TODO: if we can move migration loadvm out of main thread, then we > + * won't block main thread from polling the accept() fds. We can drop > + * this as a whole when that is done. > > Huge thanks to both! Thank you Peter :) > >> + */ >> + do { >> + if (!migrate_postcopy_preempt() || !qemu_in_coroutine() || >> + mis->postcopy_qemufile_dst) { >> + break; >> + } >> + >> + aio_co_schedule(qemu_get_current_aio_context(), qemu_coroutine_self()); >> + qemu_coroutine_yield(); >> + } while (1); >> + >> ret = qemu_loadvm_state_main(packf, mis); >> trace_loadvm_handle_cmd_packaged_main(ret); >> qemu_fclose(packf); >> -- >> 2.27.0 >> >
diff --git a/migration/savevm.c b/migration/savevm.c index 388d7af7cd..63f9991a8a 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -2342,6 +2342,23 @@ static int loadvm_handle_cmd_packaged(MigrationIncomingState *mis) QEMUFile *packf = qemu_file_new_input(QIO_CHANNEL(bioc)); + /* + * Before loading the guest states, ensure that the preempt channel has + * been ready to use, as some of the states (e.g. via virtio_load) might + * trigger page faults that will be handled through the preempt channel. + * So yield to the main thread in the case that the channel create event + * hasn't been dispatched. + */ + do { + if (!migrate_postcopy_preempt() || !qemu_in_coroutine() || + mis->postcopy_qemufile_dst) { + break; + } + + aio_co_schedule(qemu_get_current_aio_context(), qemu_coroutine_self()); + qemu_coroutine_yield(); + } while (1); + ret = qemu_loadvm_state_main(packf, mis); trace_loadvm_handle_cmd_packaged_main(ret); qemu_fclose(packf);