Re: [PATCH 5/5] spapr.c: send QAPI event when memory hotunplug fails

[David Gibson]

On Fri, Feb 26, 2021 at 01:33:01PM -0300, Daniel Henrique Barboza wrote:
> Recent changes allowed the pSeries machine to rollback the hotunplug
> process for the DIMM when the guest kernel signals, via a
> reconfiguration of the DR connector, that it's not going to release the
> LMBs.
> 
> Let's also warn QAPI listerners about it. One place to do it would be
> right after the unplug state is cleaned up,
> spapr_clear_pending_dimm_unplug_state(). This would mean that the
> function is now doing more than cleaning up the pending dimm state
> though.
> 
> This patch does the following changes in spapr.c:
> 
> - send a QAPI event to inform that we experienced a failure in the
>   hotunplug of the DIMM;
> 
> - rename spapr_clear_pending_dimm_unplug_state() to
>   spapr_memory_unplug_rollback(). This is a better fit for what the
>   function is now doing, and it makes callers care more about what the
>   function goal is and less about spapr.c internals such as clearing
>   the pending dimm unplug state.
> 
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> ---
>  hw/ppc/spapr.c         | 13 +++++++++++--
>  hw/ppc/spapr_drc.c     |  5 ++---
>  include/hw/ppc/spapr.h |  3 +--
>  3 files changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 6ef72ee7bd..cbe5cafb14 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -28,6 +28,7 @@
>  #include "qemu-common.h"
>  #include "qemu/datadir.h"
>  #include "qapi/error.h"
> +#include "qapi/qapi-events-machine.h"
>  #include "qapi/visitor.h"
>  #include "sysemu/sysemu.h"
>  #include "sysemu/hostmem.h"
> @@ -3575,14 +3576,14 @@ static SpaprDimmState 
> *spapr_recover_pending_dimm_state(SpaprMachineState *ms,
>      return spapr_pending_dimm_unplugs_add(ms, avail_lmbs, dimm);
>  }
>  
> -void spapr_clear_pending_dimm_unplug_state(SpaprMachineState *spapr,
> -                                           DeviceState *dev)
> +void spapr_memory_unplug_rollback(SpaprMachineState *spapr, DeviceState *dev)
>  {
>      SpaprDimmState *ds;
>      PCDIMMDevice *dimm;
>      SpaprDrc *drc;
>      uint32_t nr_lmbs;
>      uint64_t size, addr_start, addr;
> +    g_autofree char *qapi_error = NULL;
>      int i;
>  
>      if (!dev) {
> @@ -3616,6 +3617,14 @@ void 
> spapr_clear_pending_dimm_unplug_state(SpaprMachineState *spapr,
>          drc->unplug_requested = false;
>          addr += SPAPR_MEMORY_BLOCK_SIZE;
>      }
> +
> +    /*
> +     * Tell QAPI that something happened and the memory
> +     * hotunplug wasn't successful.
> +     */
> +    qapi_error = g_strdup_printf("Memory hotunplug failed for device %s",
> +                                 dev->id);

Might be worth adjusting the error message to make it clearer that it
was the guest which specifically rejected the unplug.  Other than
that, LGTM.

> +    qapi_event_send_mem_unplug_error(dev->id, qapi_error);
>  }
>  
>  /* Callback to be called during DRC release. */
> diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c
> index 8c4997d795..8faaf9f1dd 100644
> --- a/hw/ppc/spapr_drc.c
> +++ b/hw/ppc/spapr_drc.c
> @@ -1232,12 +1232,11 @@ static void rtas_ibm_configure_connector(PowerPCCPU 
> *cpu,
>  
>      /*
>       * This indicates that the kernel is reconfiguring a LMB due to
> -     * a failed hotunplug. Clear the pending unplug state for the whole
> -     * DIMM.
> +     * a failed hotunplug. Rollback the DIMM unplug process.
>       */
>      if (spapr_drc_type(drc) == SPAPR_DR_CONNECTOR_TYPE_LMB &&
>          drc->unplug_requested) {
> -        spapr_clear_pending_dimm_unplug_state(spapr, drc->dev);
> +        spapr_memory_unplug_rollback(spapr, drc->dev);
>      }
>  
>      if (!drc->fdt) {
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index d6edeaaaff..47cebaf3ac 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -847,8 +847,7 @@ int spapr_hpt_shift_for_ramsize(uint64_t ramsize);
>  int spapr_reallocate_hpt(SpaprMachineState *spapr, int shift, Error **errp);
>  void spapr_clear_pending_events(SpaprMachineState *spapr);
>  void spapr_clear_pending_hotplug_events(SpaprMachineState *spapr);
> -void spapr_clear_pending_dimm_unplug_state(SpaprMachineState *spapr,
> -                                           DeviceState *dev);
> +void spapr_memory_unplug_rollback(SpaprMachineState *spapr, DeviceState 
> *dev);
>  int spapr_max_server_number(SpaprMachineState *spapr);
>  void spapr_store_hpte(PowerPCCPU *cpu, hwaddr ptex,
>                        uint64_t pte0, uint64_t pte1);

-- 
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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