Re: [Qemu-ppc] [PATCH v2] powerpc/pseries: start rtasd before PCI probing
From: Greg Kurz
Date: Tue Jun 21 2016 - 13:20:25 EST
On Wed, 15 Jun 2016 22:26:41 +0200
Greg Kurz <gkurz@xxxxxxxxxxxxxxxxxx> wrote:
> A strange behaviour is observed when comparing PCI hotplug in QEMU, between
> x86 and pseries. If you consider the following steps:
> - start a VM
> - add a PCI device via the QEMU monitor before the rtasd has started (for
> example starting the VM in paused state, or hotplug during FW or boot
> loader)
> - resume the VM execution
>
> The x86 kernel detects the PCI device, but the pseries one does not.
>
> This happens because the rtasd kernel worker is currently started under
> device_initcall, while PCI probing happens earlier under subsys_initcall.
>
> As a consequence, if we have a pending RTAS event at boot time, a message
> is printed and the event is dropped.
>
> This patch moves all the initialization of rtasd to arch_initcall, which is
> run before subsys_call: this way, logging_enabled is true when the RTAS
> event pops up and it is not lost anymore.
>
> The proc fs bits stay at device_initcall because they cannot be run before
> fs_initcall.
>
> Signed-off-by: Greg Kurz <gkurz@xxxxxxxxxxxxxxxxxx>
> ---
> v2: - avoid behaviour change: don't create the proc entry if early init failed
>
I forgot to mention that Thomas had sent a Tested-by for v1, which I think is
still valid for v2.
> Michael,
>
> This was also tested under PowerVM: it doesn't fix anything there because the
> HMC tells it won't honor DLPAR features as long as the RMC isn't here, which
> happens later in the boot sequence. It hence seems impossible to have a pending
> RTAS event at boot time.
>
> It doesn't seem to break anything either, the kernel boots and hotplug works
> okay once the RMC is up.
>
> Cheers.
>
> --
> Greg
>
> ---
> arch/powerpc/kernel/rtasd.c | 22 +++++++++++++++++-----
> 1 file changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/kernel/rtasd.c b/arch/powerpc/kernel/rtasd.c
> index e864b7c5884e..a26a02006576 100644
> --- a/arch/powerpc/kernel/rtasd.c
> +++ b/arch/powerpc/kernel/rtasd.c
> @@ -526,10 +526,8 @@ void rtas_cancel_event_scan(void)
> }
> EXPORT_SYMBOL_GPL(rtas_cancel_event_scan);
>
> -static int __init rtas_init(void)
> +static int __init rtas_event_scan_init(void)
> {
> - struct proc_dir_entry *entry;
> -
> if (!machine_is(pseries) && !machine_is(chrp))
> return 0;
>
> @@ -562,13 +560,27 @@ static int __init rtas_init(void)
> return -ENOMEM;
> }
>
> + start_event_scan();
> +
> + return 0;
> +}
> +arch_initcall(rtas_event_scan_init);
> +
> +static int __init rtas_init(void)
> +{
> + struct proc_dir_entry *entry;
> +
> + if (!machine_is(pseries) && !machine_is(chrp))
> + return 0;
> +
> + if (!rtas_log_buf)
> + return -ENODEV;
> +
> entry = proc_create("powerpc/rtas/error_log", S_IRUSR, NULL,
> &proc_rtas_log_operations);
> if (!entry)
> printk(KERN_ERR "Failed to create error_log proc entry\n");
>
> - start_event_scan();
> -
> return 0;
> }
> __initcall(rtas_init);
>
>