Re: [PATCH 4/6] spapr: Use spapr_drc_reset_all() at machine reset

[David Gibson]

On Fri, Dec 18, 2020 at 11:33:58AM +0100, Greg Kurz wrote:
> Documentation of object_child_foreach_recursive() clearly stipulates
> that "it is forbidden to add or remove children from @obj from the @fn
> callback". But this is exactly what we do during machine reset. The call
> to spapr_drc_reset() can finalize the hot-unplug sequence of a PHB or a
> PCI bridge, both of which will then in turn destroy their PCI DRCs. This
> could potentially invalidate the iterator used by do_object_child_foreach().
> It is pure luck that this haven't caused any issues so far.
> 
> Use spapr_drc_reset_all() since it can cope with DRC removal.
> 
> Signed-off-by: Greg Kurz 

Applied, thanks.

> ---
>  hw/ppc/spapr.c | 15 +--
>  1 file changed, 1 insertion(+), 14 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 43dded87f498..8528bc90fec4 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1566,19 +1566,6 @@ void spapr_setup_hpt(SpaprMachineState *spapr)
>  }
>  }
>  
> -static int spapr_reset_drcs(Object *child, void *opaque)
> -{
> -SpaprDrc *drc =
> -(SpaprDrc *) object_dynamic_cast(child,
> - TYPE_SPAPR_DR_CONNECTOR);
> -
> -if (drc) {
> -spapr_drc_reset(drc);
> -}
> -
> -return 0;
> -}
> -
>  static void spapr_machine_reset(MachineState *machine)
>  {
>  SpaprMachineState *spapr = SPAPR_MACHINE(machine);
> @@ -1633,7 +1620,7 @@ static void spapr_machine_reset(MachineState *machine)
>   * will crash QEMU if the DIMM holding the vring goes away). To avoid 
> such
>   * situations, we reset DRCs after all devices have been reset.
>   */
> -object_child_foreach_recursive(object_get_root(), spapr_reset_drcs, 
> NULL);
> +spapr_drc_reset_all(spapr);
>  
>  spapr_clear_pending_events(spapr);
>  

-- 
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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Re: [PATCH 4/6] spapr: Use spapr_drc_reset_all() at machine reset

[Daniel Henrique Barboza]

On 12/18/20 7:33 AM, Greg Kurz wrote:

Documentation of object_child_foreach_recursive() clearly stipulates
that "it is forbidden to add or remove children from @obj from the @fn
callback". But this is exactly what we do during machine reset. The call
to spapr_drc_reset() can finalize the hot-unplug sequence of a PHB or a
PCI bridge, both of which will then in turn destroy their PCI DRCs. This
could potentially invalidate the iterator used by do_object_child_foreach().
It is pure luck that this haven't caused any issues so far.

Use spapr_drc_reset_all() since it can cope with DRC removal.

Signed-off-by: Greg Kurz 
---


Reviewed-by: Daniel Henrique Barboza 


  hw/ppc/spapr.c | 15 +--
  1 file changed, 1 insertion(+), 14 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 43dded87f498..8528bc90fec4 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1566,19 +1566,6 @@ void spapr_setup_hpt(SpaprMachineState *spapr)
  }
  }
  
-static int spapr_reset_drcs(Object *child, void *opaque)

-{
-SpaprDrc *drc =
-(SpaprDrc *) object_dynamic_cast(child,
- TYPE_SPAPR_DR_CONNECTOR);
-
-if (drc) {
-spapr_drc_reset(drc);
-}
-
-return 0;
-}
-
  static void spapr_machine_reset(MachineState *machine)
  {
  SpaprMachineState *spapr = SPAPR_MACHINE(machine);
@@ -1633,7 +1620,7 @@ static void spapr_machine_reset(MachineState *machine)
   * will crash QEMU if the DIMM holding the vring goes away). To avoid such
   * situations, we reset DRCs after all devices have been reset.
   */
-object_child_foreach_recursive(object_get_root(), spapr_reset_drcs, NULL);
+spapr_drc_reset_all(spapr);
  
  spapr_clear_pending_events(spapr);
  

[PATCH 4/6] spapr: Use spapr_drc_reset_all() at machine reset

[Greg Kurz]

Documentation of object_child_foreach_recursive() clearly stipulates
that "it is forbidden to add or remove children from @obj from the @fn
callback". But this is exactly what we do during machine reset. The call
to spapr_drc_reset() can finalize the hot-unplug sequence of a PHB or a
PCI bridge, both of which will then in turn destroy their PCI DRCs. This
could potentially invalidate the iterator used by do_object_child_foreach().
It is pure luck that this haven't caused any issues so far.

Use spapr_drc_reset_all() since it can cope with DRC removal.

Signed-off-by: Greg Kurz 
---
 hw/ppc/spapr.c | 15 +--
 1 file changed, 1 insertion(+), 14 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 43dded87f498..8528bc90fec4 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1566,19 +1566,6 @@ void spapr_setup_hpt(SpaprMachineState *spapr)
 }
 }
 
-static int spapr_reset_drcs(Object *child, void *opaque)
-{
-SpaprDrc *drc =
-(SpaprDrc *) object_dynamic_cast(child,
- TYPE_SPAPR_DR_CONNECTOR);
-
-if (drc) {
-spapr_drc_reset(drc);
-}
-
-return 0;
-}
-
 static void spapr_machine_reset(MachineState *machine)
 {
 SpaprMachineState *spapr = SPAPR_MACHINE(machine);
@@ -1633,7 +1620,7 @@ static void spapr_machine_reset(MachineState *machine)
  * will crash QEMU if the DIMM holding the vring goes away). To avoid such
  * situations, we reset DRCs after all devices have been reset.
  */
-object_child_foreach_recursive(object_get_root(), spapr_reset_drcs, NULL);
+spapr_drc_reset_all(spapr);
 
 spapr_clear_pending_events(spapr);
 
-- 
2.26.2