Hi, > -----Original Message----- > From: Xen-devel <[email protected]> On Behalf Of > Sebastian Andrzej Siewior > Sent: Monday, November 22, 2021 11:47 PM > To: Longpeng (Mike, Cloud Infrastructure Service Product Dept.) > <[email protected]> > Cc: [email protected]; Gonglei (Arei) <[email protected]>; > [email protected]; [email protected]; Peter Zijlstra > <[email protected]>; Ingo Molnar <[email protected]>; Valentin > Schneider <[email protected]>; Boris Ostrovsky > <[email protected]>; Juergen Gross <[email protected]>; Stefano > Stabellini <[email protected]>; Thomas Gleixner <[email protected]>; > Ingo Molnar <[email protected]>; Borislav Petkov <[email protected]>; Dave > Hansen <[email protected]>; H. Peter Anvin <[email protected]> > Subject: [PATCH] cpu/hotplug: Allow the CPU in CPU_UP_PREPARE state to be > brought up again. > > From: "Longpeng(Mike)" <[email protected]> > > A CPU will not show up in virtualized environment which includes an > Enclave. The VM splits its resources into a primary VM and a Enclave > VM. While the Enclave is active, the hypervisor will ignore all requests > to bring up a CPU and this CPU will remain in CPU_UP_PREPARE state. > The kernel will wait up to ten seconds for CPU to show up > (do_boot_cpu()) and then rollback the hotplug state back to > CPUHP_OFFLINE leaving the CPU state in CPU_UP_PREPARE. The CPU state is > set back to CPUHP_TEARDOWN_CPU during the CPU_POST_DEAD stage. > > After the Enclave VM terminates, the primary VM can bring up the CPU > again. > > Allow to bring up the CPU if it is in the CPU_UP_PREPARE state. > > [bigeasy: Rewrite commit description.] > > Signed-off-by: Longpeng(Mike) <[email protected]> > Signed-off-by: Sebastian Andrzej Siewior <[email protected]> > Link: https://lore.kernel.org/r/20210901051143.2752-1- > [email protected] > --- > > For XEN: this changes the behaviour as it allows to invoke > cpu_initialize_context() again should it have have earlier. I *think* > this is okay and would to bring up the CPU again should the memory > allocation in cpu_initialize_context() fail. > > kernel/smpboot.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/kernel/smpboot.c b/kernel/smpboot.c > index f6bc0bc8a2aab..34958d7fe2c1c 100644 > --- a/kernel/smpboot.c > +++ b/kernel/smpboot.c > @@ -392,6 +392,13 @@ int cpu_check_up_prepare(int cpu) > */ > return -EAGAIN; > > + case CPU_UP_PREPARE: > + /* > + * Timeout while waiting for the CPU to show up. Allow to try > + * again later. > + */ > + return 0; > + > default: > > /* Should not happen. Famous last words. */ > -- > 2.33.1 >
Reviewed-by: Henry Wang <[email protected]> Kind regards, Henry
