From 336f560a8917fd60bcdb71b97263257611411453 Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Fri, 25 Nov 2022 07:32:47 +0100 Subject: [PATCH] x86/xen: don't let xen_pv_play_dead() return A function called via the paravirt play_dead() hook should not return to the caller. xen_pv_play_dead() has a problem in this regard, as it currently will return in case an offlined cpu is brought to life again. This can be changed only by doing basically a longjmp() to cpu_bringup_and_idle(), as the hypercall for bringing down the cpu will just return when the cpu is coming up again. Just re-initializing the cpu isn't possible, as the Xen hypervisor will deny that operation. So introduce xen_cpu_bringup_again() resetting the stack and calling cpu_bringup_and_idle(), which can be called after HYPERVISOR_vcpu_op() in xen_pv_play_dead(). Signed-off-by: Juergen Gross Reviewed-by: Boris Ostrovsky Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20221125063248.30256-2-jgross@suse.com Signed-off-by: Juergen Gross --- arch/x86/xen/smp.h | 2 ++ arch/x86/xen/smp_pv.c | 13 ++----------- arch/x86/xen/xen-head.S | 7 +++++++ 3 files changed, 11 insertions(+), 11 deletions(-) diff --git a/arch/x86/xen/smp.h b/arch/x86/xen/smp.h index bd02f9d50107..6e90a312067b 100644 --- a/arch/x86/xen/smp.h +++ b/arch/x86/xen/smp.h @@ -21,6 +21,8 @@ void xen_smp_send_reschedule(int cpu); void xen_smp_send_call_function_ipi(const struct cpumask *mask); void xen_smp_send_call_function_single_ipi(int cpu); +void xen_cpu_bringup_again(unsigned long stack); + struct xen_common_irq { int irq; char *name; diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c index 6175f2c5c822..a97b0505a483 100644 --- a/arch/x86/xen/smp_pv.c +++ b/arch/x86/xen/smp_pv.c @@ -385,17 +385,8 @@ static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */ { play_dead_common(); HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL); - cpu_bringup(); - /* - * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down) - * clears certain data that the cpu_idle loop (which called us - * and that we return from) expects. The only way to get that - * data back is to call: - */ - tick_nohz_idle_enter(); - tick_nohz_idle_stop_tick_protected(); - - cpuhp_online_idle(CPUHP_AP_ONLINE_IDLE); + xen_cpu_bringup_again((unsigned long)task_pt_regs(current)); + BUG(); } #else /* !CONFIG_HOTPLUG_CPU */ diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index ffaa62167f6e..e36ea4268bd2 100644 --- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -76,6 +76,13 @@ SYM_CODE_START(asm_cpu_bringup_and_idle) call cpu_bringup_and_idle SYM_CODE_END(asm_cpu_bringup_and_idle) + +SYM_CODE_START(xen_cpu_bringup_again) + UNWIND_HINT_FUNC + mov %rdi, %rsp + UNWIND_HINT_REGS + call cpu_bringup_and_idle +SYM_CODE_END(xen_cpu_bringup_again) .popsection #endif #endif