Re: [PATCH 1/1] spapr_drc.c: handle hotunplug errors in drc_unisolate_logical()

[David Gibson]

On Fri, Apr 16, 2021 at 06:09:41PM -0300, Daniel Henrique Barboza wrote:
> The Linux kernel will call set-indicator to move a DRC to 'unisolate' in
> the case a device removal fails. Setting a DRC that is already

Only issue I have with this patch is that this isn't quite accurate
yet.  Can you reword this to include some of the rationale from the
cover letters about how a previous no-op is a safe choice to allow
guest->hv error signalling and that we expect the Linux kernel to use
it at some point.

> unisolated or configured to 'unisolate' is a no-op for the current
> hypervisors that supports pSeries guests, namely QEMU and phyp, and is
> being used to signal hotunplug errors if the hypervisor has the code for
> it.
> 
> This patch changes drc_unisolate_logical() to implement in the pSeries
> machine. For CPUs it's a simple matter of setting drc->unplug_requested
> to 'false', while for LMBs the process is similar to the rollback that
> is done in rtas_ibm_configure_connector(). Although at this moment the
> Linux kernel is only reporting CPU removal errors, let's get the code
> ready to handle LMBs as well.
> 
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>

Otherwise,

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  hw/ppc/spapr_drc.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c
> index 9e16505fa1..6918e0c9d1 100644
> --- a/hw/ppc/spapr_drc.c
> +++ b/hw/ppc/spapr_drc.c
> @@ -151,9 +151,32 @@ static uint32_t drc_isolate_logical(SpaprDrc *drc)
>  
>  static uint32_t drc_unisolate_logical(SpaprDrc *drc)
>  {
> +    SpaprMachineState *spapr = NULL;
> +
>      switch (drc->state) {
>      case SPAPR_DRC_STATE_LOGICAL_UNISOLATE:
>      case SPAPR_DRC_STATE_LOGICAL_CONFIGURED:
> +        /*
> +         * Unisolating a logical DRC that was marked for unplug
> +         * means that the kernel is refusing the removal.
> +         */
> +        if (drc->unplug_requested && drc->dev) {
> +            if (spapr_drc_type(drc) == SPAPR_DR_CONNECTOR_TYPE_LMB) {
> +                spapr = SPAPR_MACHINE(qdev_get_machine());
> +
> +                spapr_memory_unplug_rollback(spapr, drc->dev);
> +            }
> +
> +            drc->unplug_requested = false;
> +            error_report("Device hotunplug rejected by the guest "
> +                         "for device %s", drc->dev->id);
> +
> +            /*
> +             * TODO: send a QAPI DEVICE_UNPLUG_ERROR event when
> +             * it is implemented.
> +             */
> +        }
> +
>          return RTAS_OUT_SUCCESS; /* Nothing to do */
>      case SPAPR_DRC_STATE_LOGICAL_AVAILABLE:
>          break; /* see below */

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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