[tip:,objtool/core] x86/xen: don't let xen_pv_play_dead() return
Commit Message
The following commit has been merged into the objtool/core branch of tip:
Commit-ID: 076cbf5d216377087e135a0ae81844f7835cdc15
Gitweb: https://git.kernel.org/tip/076cbf5d216377087e135a0ae81844f7835cdc15
Author: Juergen Gross <jgross@suse.com>
AuthorDate: Fri, 25 Nov 2022 07:32:47 +01:00
Committer: Juergen Gross <jgross@suse.com>
CommitterDate: Tue, 17 Jan 2023 09:05:28 +01:00
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 <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20221125063248.30256-2-jgross@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>
---
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(-)
@@ -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;
@@ -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 */
@@ -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