Re: [Qemu-ppc] [FIX PATCH v2] spapr: Fix QEMU abort during memory unplug

[David Gibson]

On Fri, Jul 21, 2017 at 10:21:06AM +0530, Bharata B Rao wrote:
> Commit 0cffce56 (hw/ppc/spapr.c: adding pending_dimm_unplugs to
> sPAPRMachineState) introduced a new way to track pending LMBs of DIMM
> device that is marked for removal. Since this commit we can hit the
> assert in spapr_pending_dimm_unplugs_add() in the following situation:
> 
> - DIMM device removal fails as the guest doesn't allow the removal.
> - Subsequent attempt to remove the same DIMM would hit the assert
>   as the corresponding sPAPRDIMMState is still part of the
>   pending_dimm_unplugs list.
> 
> Fix this by removing the assert and conditionally adding the
> sPAPRDIMMState to pending_dimm_unplugs list only when it is not
> already present.
> 
> Fixes: 0cffce56ae3501c5783d779f97993ce478acf856
> Signed-off-by: Bharata B Rao <address@hidden>

Applied to ppc-for-2.10.

> ---
> Changes in v2:
> - sPAPRDIMMState is now allocated within spapr_pending_dimm_unplugs_add()
>   itself (David Gibson)
> - spapr_recover_pending_dimm_state() should never return a NULL 
> sPAPRDIMMState,
>   added an assert for the same.
> 
>  hw/ppc/spapr.c | 37 +++++++++++++++++++++----------------
>  1 file changed, 21 insertions(+), 16 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 1cb09e7..2465b27 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2850,11 +2850,25 @@ static sPAPRDIMMState 
> *spapr_pending_dimm_unplugs_find(sPAPRMachineState *s,
>      return dimm_state;
>  }
>  
> -static void spapr_pending_dimm_unplugs_add(sPAPRMachineState *spapr,
> -                                           sPAPRDIMMState *dimm_state)
> +static sPAPRDIMMState *spapr_pending_dimm_unplugs_add(sPAPRMachineState 
> *spapr,
> +                                                      uint32_t nr_lmbs,
> +                                                      PCDIMMDevice *dimm)
>  {
> -    g_assert(!spapr_pending_dimm_unplugs_find(spapr, dimm_state->dimm));
> -    QTAILQ_INSERT_HEAD(&spapr->pending_dimm_unplugs, dimm_state, next);
> +    sPAPRDIMMState *ds = NULL;
> +
> +    /*
> +     * If this request is for a DIMM whose removal had failed earlier
> +     * (due to guest's refusal to remove the LMBs), we would have this
> +     * dimm already in the pending_dimm_unplugs list. In that
> +     * case don't add again.
> +     */
> +    if (!spapr_pending_dimm_unplugs_find(spapr, dimm)) {
> +        ds = g_malloc0(sizeof(sPAPRDIMMState));
> +        ds->nr_lmbs = nr_lmbs;
> +        ds->dimm = dimm;
> +        QTAILQ_INSERT_HEAD(&spapr->pending_dimm_unplugs, ds, next);
> +    }
> +    return ds;
>  }
>  
>  static void spapr_pending_dimm_unplugs_remove(sPAPRMachineState *spapr,
> @@ -2875,7 +2889,6 @@ static sPAPRDIMMState 
> *spapr_recover_pending_dimm_state(sPAPRMachineState *ms,
>      uint32_t avail_lmbs = 0;
>      uint64_t addr_start, addr;
>      int i;
> -    sPAPRDIMMState *ds;
>  
>      addr_start = object_property_get_int(OBJECT(dimm), PC_DIMM_ADDR_PROP,
>                                           &error_abort);
> @@ -2891,11 +2904,7 @@ static sPAPRDIMMState 
> *spapr_recover_pending_dimm_state(sPAPRMachineState *ms,
>          addr += SPAPR_MEMORY_BLOCK_SIZE;
>      }
>  
> -    ds = g_malloc0(sizeof(sPAPRDIMMState));
> -    ds->nr_lmbs = avail_lmbs;
> -    ds->dimm = dimm;
> -    spapr_pending_dimm_unplugs_add(ms, ds);
> -    return ds;
> +    return spapr_pending_dimm_unplugs_add(ms, avail_lmbs, dimm);
>  }
>  
>  /* Callback to be called during DRC release. */
> @@ -2911,6 +2920,7 @@ void spapr_lmb_release(DeviceState *dev)
>       * during the unplug process. In this case recover it. */
>      if (ds == NULL) {
>          ds = spapr_recover_pending_dimm_state(spapr, PC_DIMM(dev));
> +        g_assert(ds);
>          /* The DRC being examined by the caller at least must be counted */
>          g_assert(ds->nr_lmbs);
>      }
> @@ -2942,18 +2952,13 @@ static void 
> spapr_memory_unplug_request(HotplugHandler *hotplug_dev,
>      uint64_t addr_start, addr;
>      int i;
>      sPAPRDRConnector *drc;
> -    sPAPRDIMMState *ds;
> -
>      addr_start = object_property_get_uint(OBJECT(dimm), PC_DIMM_ADDR_PROP,
>                                           &local_err);
>      if (local_err) {
>          goto out;
>      }
>  
> -    ds = g_malloc0(sizeof(sPAPRDIMMState));
> -    ds->nr_lmbs = nr_lmbs;
> -    ds->dimm = dimm;
> -    spapr_pending_dimm_unplugs_add(spapr, ds);
> +    spapr_pending_dimm_unplugs_add(spapr, nr_lmbs, dimm);
>  
>      addr = addr_start;
>      for (i = 0; i < nr_lmbs; i++) {

-- 
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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