[PATCH] spapr_numa.c: fixes in spapr_numa_FORM2_write_rtas_tables()

[PATCH] spapr_numa.c: fixes in spapr_numa_FORM2_write_rtas_tables()

[Daniel Henrique Barboza]

This patch has a handful of modifications for the recent added
FORM2 support:

- there is no particular reason for both 'lookup_index_table' and
'distance_table' to be allocated in the heap, since their sizes are
known right at the start of the function. Use static allocation in
them to spare a couple of g_new0() calls;

- to not allocate more than the necessary size in 'distance_table'. At
this moment the array is oversized due to allocating uint32_t for all
elements, when most of them fits in an uint8_t;

- create a NUMA_LOCAL_DISTANCE macro to avoid hardcoding the local
distance value.

Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
---
 hw/ppc/spapr_numa.c | 35 +++++++++++++++++++----------------
 1 file changed, 19 insertions(+), 16 deletions(-)

diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c
index 58d5dc7084..039a0439c6 100644
--- a/hw/ppc/spapr_numa.c
+++ b/hw/ppc/spapr_numa.c
@@ -19,6 +19,9 @@
 /* Moved from hw/ppc/spapr_pci_nvlink2.c */
 #define SPAPR_GPU_NUMA_ID           (cpu_to_be32(1))
 
+/* Macro to avoid hardcoding the local distance value */
+#define NUMA_LOCAL_DISTANCE         10
+
 /*
  * Retrieves max_dist_ref_points of the current NUMA affinity.
  */
@@ -500,17 +503,21 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
     MachineState *ms = MACHINE(spapr);
     NodeInfo *numa_info = ms->numa_state->nodes;
     int nb_numa_nodes = ms->numa_state->num_nodes;
+    /* Lookup index table has an extra uint32_t with its length */
+    uint32_t lookup_index_table[nb_numa_nodes + 1];
     int distance_table_entries = nb_numa_nodes * nb_numa_nodes;
-    g_autofree uint32_t *lookup_index_table = NULL;
-    g_autofree uint32_t *distance_table = NULL;
-    int src, dst, i, distance_table_size;
-    uint8_t *node_distances;
+    /*
+     * Distance table is an uint8_t array with a leading uint32_t
+     * containing its length.
+     */
+    uint8_t distance_table[distance_table_entries + 4];
+    uint32_t *distance_table_length;
+    int src, dst, i;
 
     /*
      * ibm,numa-lookup-index-table: array with length and a
      * list of NUMA ids present in the guest.
      */
-    lookup_index_table = g_new0(uint32_t, nb_numa_nodes + 1);
     lookup_index_table[0] = cpu_to_be32(nb_numa_nodes);
 
     for (i = 0; i < nb_numa_nodes; i++) {
@@ -518,8 +525,7 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
     }
 
     _FDT(fdt_setprop(fdt, rtas, "ibm,numa-lookup-index-table",
-                     lookup_index_table,
-                     (nb_numa_nodes + 1) * sizeof(uint32_t)));
+                     lookup_index_table, sizeof(lookup_index_table)));
 
     /*
      * ibm,numa-distance-table: contains all node distances. First
@@ -531,11 +537,10 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
      * array because NUMA ids can be sparse (node 0 is the first,
      * node 8 is the second ...).
      */
-    distance_table = g_new0(uint32_t, distance_table_entries + 1);
-    distance_table[0] = cpu_to_be32(distance_table_entries);
+    distance_table_length = (uint32_t *)distance_table;
+    distance_table_length[0] = cpu_to_be32(distance_table_entries);
 
-    node_distances = (uint8_t *)&distance_table[1];
-    i = 0;
+    i = 4;
 
     for (src = 0; src < nb_numa_nodes; src++) {
         for (dst = 0; dst < nb_numa_nodes; dst++) {
@@ -546,18 +551,16 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
              * adding the numa_info to retrieve distance info from.
              */
             if (src == dst) {
-                node_distances[i++] = 10;
+                distance_table[i++] = NUMA_LOCAL_DISTANCE;
                 continue;
             }
 
-            node_distances[i++] = numa_info[src].distance[dst];
+            distance_table[i++] = numa_info[src].distance[dst];
         }
     }
 
-    distance_table_size = distance_table_entries * sizeof(uint8_t) +
-                          sizeof(uint32_t);
     _FDT(fdt_setprop(fdt, rtas, "ibm,numa-distance-table",
-                     distance_table, distance_table_size));
+                     distance_table, sizeof(distance_table)));
 }
 
 /*
-- 
2.31.1

Re: [PATCH] spapr_numa.c: fixes in spapr_numa_FORM2_write_rtas_tables()

[David Gibson]

[-- Attachment #1: Type: text/plain, Size: 4851 bytes --]

On Tue, Sep 21, 2021 at 04:43:47PM -0300, Daniel Henrique Barboza wrote:
> This patch has a handful of modifications for the recent added
> FORM2 support:
> 
> - there is no particular reason for both 'lookup_index_table' and
> 'distance_table' to be allocated in the heap, since their sizes are
> known right at the start of the function. Use static allocation in
> them to spare a couple of g_new0() calls;
> 
> - to not allocate more than the necessary size in 'distance_table'. At
> this moment the array is oversized due to allocating uint32_t for all
> elements, when most of them fits in an uint8_t;
> 
> - create a NUMA_LOCAL_DISTANCE macro to avoid hardcoding the local
> distance value.
> 
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>

Applied to ppc-fot-6.2, thanks.

> ---
>  hw/ppc/spapr_numa.c | 35 +++++++++++++++++++----------------
>  1 file changed, 19 insertions(+), 16 deletions(-)
> 
> diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c
> index 58d5dc7084..039a0439c6 100644
> --- a/hw/ppc/spapr_numa.c
> +++ b/hw/ppc/spapr_numa.c
> @@ -19,6 +19,9 @@
>  /* Moved from hw/ppc/spapr_pci_nvlink2.c */
>  #define SPAPR_GPU_NUMA_ID           (cpu_to_be32(1))
>  
> +/* Macro to avoid hardcoding the local distance value */
> +#define NUMA_LOCAL_DISTANCE         10
> +
>  /*
>   * Retrieves max_dist_ref_points of the current NUMA affinity.
>   */
> @@ -500,17 +503,21 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>      MachineState *ms = MACHINE(spapr);
>      NodeInfo *numa_info = ms->numa_state->nodes;
>      int nb_numa_nodes = ms->numa_state->num_nodes;
> +    /* Lookup index table has an extra uint32_t with its length */
> +    uint32_t lookup_index_table[nb_numa_nodes + 1];
>      int distance_table_entries = nb_numa_nodes * nb_numa_nodes;
> -    g_autofree uint32_t *lookup_index_table = NULL;
> -    g_autofree uint32_t *distance_table = NULL;
> -    int src, dst, i, distance_table_size;
> -    uint8_t *node_distances;
> +    /*
> +     * Distance table is an uint8_t array with a leading uint32_t
> +     * containing its length.
> +     */
> +    uint8_t distance_table[distance_table_entries + 4];
> +    uint32_t *distance_table_length;
> +    int src, dst, i;
>  
>      /*
>       * ibm,numa-lookup-index-table: array with length and a
>       * list of NUMA ids present in the guest.
>       */
> -    lookup_index_table = g_new0(uint32_t, nb_numa_nodes + 1);
>      lookup_index_table[0] = cpu_to_be32(nb_numa_nodes);
>  
>      for (i = 0; i < nb_numa_nodes; i++) {
> @@ -518,8 +525,7 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>      }
>  
>      _FDT(fdt_setprop(fdt, rtas, "ibm,numa-lookup-index-table",
> -                     lookup_index_table,
> -                     (nb_numa_nodes + 1) * sizeof(uint32_t)));
> +                     lookup_index_table, sizeof(lookup_index_table)));
>  
>      /*
>       * ibm,numa-distance-table: contains all node distances. First
> @@ -531,11 +537,10 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>       * array because NUMA ids can be sparse (node 0 is the first,
>       * node 8 is the second ...).
>       */
> -    distance_table = g_new0(uint32_t, distance_table_entries + 1);
> -    distance_table[0] = cpu_to_be32(distance_table_entries);
> +    distance_table_length = (uint32_t *)distance_table;
> +    distance_table_length[0] = cpu_to_be32(distance_table_entries);
>  
> -    node_distances = (uint8_t *)&distance_table[1];
> -    i = 0;
> +    i = 4;
>  
>      for (src = 0; src < nb_numa_nodes; src++) {
>          for (dst = 0; dst < nb_numa_nodes; dst++) {
> @@ -546,18 +551,16 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>               * adding the numa_info to retrieve distance info from.
>               */
>              if (src == dst) {
> -                node_distances[i++] = 10;
> +                distance_table[i++] = NUMA_LOCAL_DISTANCE;
>                  continue;
>              }
>  
> -            node_distances[i++] = numa_info[src].distance[dst];
> +            distance_table[i++] = numa_info[src].distance[dst];
>          }
>      }
>  
> -    distance_table_size = distance_table_entries * sizeof(uint8_t) +
> -                          sizeof(uint32_t);
>      _FDT(fdt_setprop(fdt, rtas, "ibm,numa-distance-table",
> -                     distance_table, distance_table_size));
> +                     distance_table, sizeof(distance_table)));
>  }
>  
>  /*

-- 
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

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: [PATCH] spapr_numa.c: fixes in spapr_numa_FORM2_write_rtas_tables()

[Greg Kurz]

On Tue, 21 Sep 2021 16:43:47 -0300
Daniel Henrique Barboza <danielhb413@gmail.com> wrote:

> This patch has a handful of modifications for the recent added
> FORM2 support:
> 
> - there is no particular reason for both 'lookup_index_table' and
> 'distance_table' to be allocated in the heap, since their sizes are
> known right at the start of the function. Use static allocation in
> them to spare a couple of g_new0() calls;
> 
> - to not allocate more than the necessary size in 'distance_table'. At
> this moment the array is oversized due to allocating uint32_t for all
> elements, when most of them fits in an uint8_t;
> 
> - create a NUMA_LOCAL_DISTANCE macro to avoid hardcoding the local
> distance value.
> 

Not needed. A notion of minimal distance, which is obviously
synonymous to local, already exists in the "sysemu/numa.h"
header :

#define NUMA_DISTANCE_MIN         10

> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> ---
>  hw/ppc/spapr_numa.c | 35 +++++++++++++++++++----------------
>  1 file changed, 19 insertions(+), 16 deletions(-)
> 
> diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c
> index 58d5dc7084..039a0439c6 100644
> --- a/hw/ppc/spapr_numa.c
> +++ b/hw/ppc/spapr_numa.c
> @@ -19,6 +19,9 @@
>  /* Moved from hw/ppc/spapr_pci_nvlink2.c */
>  #define SPAPR_GPU_NUMA_ID           (cpu_to_be32(1))
>  
> +/* Macro to avoid hardcoding the local distance value */
> +#define NUMA_LOCAL_DISTANCE         10
> +
>  /*
>   * Retrieves max_dist_ref_points of the current NUMA affinity.
>   */
> @@ -500,17 +503,21 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>      MachineState *ms = MACHINE(spapr);
>      NodeInfo *numa_info = ms->numa_state->nodes;
>      int nb_numa_nodes = ms->numa_state->num_nodes;
> +    /* Lookup index table has an extra uint32_t with its length */
> +    uint32_t lookup_index_table[nb_numa_nodes + 1];
>      int distance_table_entries = nb_numa_nodes * nb_numa_nodes;
> -    g_autofree uint32_t *lookup_index_table = NULL;
> -    g_autofree uint32_t *distance_table = NULL;
> -    int src, dst, i, distance_table_size;
> -    uint8_t *node_distances;
> +    /*
> +     * Distance table is an uint8_t array with a leading uint32_t
> +     * containing its length.
> +     */
> +    uint8_t distance_table[distance_table_entries + 4];
> +    uint32_t *distance_table_length;
> +    int src, dst, i;
>  
>      /*
>       * ibm,numa-lookup-index-table: array with length and a
>       * list of NUMA ids present in the guest.
>       */
> -    lookup_index_table = g_new0(uint32_t, nb_numa_nodes + 1);
>      lookup_index_table[0] = cpu_to_be32(nb_numa_nodes);
>  
>      for (i = 0; i < nb_numa_nodes; i++) {
> @@ -518,8 +525,7 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>      }
>  
>      _FDT(fdt_setprop(fdt, rtas, "ibm,numa-lookup-index-table",
> -                     lookup_index_table,
> -                     (nb_numa_nodes + 1) * sizeof(uint32_t)));
> +                     lookup_index_table, sizeof(lookup_index_table)));
>  
>      /*
>       * ibm,numa-distance-table: contains all node distances. First
> @@ -531,11 +537,10 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>       * array because NUMA ids can be sparse (node 0 is the first,
>       * node 8 is the second ...).
>       */
> -    distance_table = g_new0(uint32_t, distance_table_entries + 1);
> -    distance_table[0] = cpu_to_be32(distance_table_entries);
> +    distance_table_length = (uint32_t *)distance_table;
> +    distance_table_length[0] = cpu_to_be32(distance_table_entries);
>  
> -    node_distances = (uint8_t *)&distance_table[1];
> -    i = 0;
> +    i = 4;
>  

A comment reminding why we're doing that wouldn't hurt, e.g.

/* Skip the array size (uint32_t) */

With these fixed, especially using NUMA_DISTANCE_MIN, you
can add:

Reviewed-by: Greg Kurz <groug@kaod.org>

>      for (src = 0; src < nb_numa_nodes; src++) {
>          for (dst = 0; dst < nb_numa_nodes; dst++) {
> @@ -546,18 +551,16 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>               * adding the numa_info to retrieve distance info from.
>               */
>              if (src == dst) {
> -                node_distances[i++] = 10;
> +                distance_table[i++] = NUMA_LOCAL_DISTANCE;
>                  continue;
>              }
>  
> -            node_distances[i++] = numa_info[src].distance[dst];
> +            distance_table[i++] = numa_info[src].distance[dst];
>          }
>      }
>  
> -    distance_table_size = distance_table_entries * sizeof(uint8_t) +
> -                          sizeof(uint32_t);
>      _FDT(fdt_setprop(fdt, rtas, "ibm,numa-distance-table",
> -                     distance_table, distance_table_size));
> +                     distance_table, sizeof(distance_table)));
>  }
>  
>  /*

Re: [PATCH] spapr_numa.c: fixes in spapr_numa_FORM2_write_rtas_tables()

[BALATON Zoltan]

On Wed, 22 Sep 2021, Greg Kurz wrote:
> On Tue, 21 Sep 2021 16:43:47 -0300
> Daniel Henrique Barboza <danielhb413@gmail.com> wrote:
>
>> This patch has a handful of modifications for the recent added
>> FORM2 support:
>>
>> - there is no particular reason for both 'lookup_index_table' and
>> 'distance_table' to be allocated in the heap, since their sizes are
>> known right at the start of the function. Use static allocation in
>> them to spare a couple of g_new0() calls;
>>
>> - to not allocate more than the necessary size in 'distance_table'. At
>> this moment the array is oversized due to allocating uint32_t for all
>> elements, when most of them fits in an uint8_t;
>>
>> - create a NUMA_LOCAL_DISTANCE macro to avoid hardcoding the local
>> distance value.
>>
>
> Not needed. A notion of minimal distance, which is obviously
> synonymous to local, already exists in the "sysemu/numa.h"
> header :
>
> #define NUMA_DISTANCE_MIN         10
>
>> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
>> ---
>>  hw/ppc/spapr_numa.c | 35 +++++++++++++++++++----------------
>>  1 file changed, 19 insertions(+), 16 deletions(-)
>>
>> diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c
>> index 58d5dc7084..039a0439c6 100644
>> --- a/hw/ppc/spapr_numa.c
>> +++ b/hw/ppc/spapr_numa.c
>> @@ -19,6 +19,9 @@
>>  /* Moved from hw/ppc/spapr_pci_nvlink2.c */
>>  #define SPAPR_GPU_NUMA_ID           (cpu_to_be32(1))
>>
>> +/* Macro to avoid hardcoding the local distance value */
>> +#define NUMA_LOCAL_DISTANCE         10
>> +
>>  /*
>>   * Retrieves max_dist_ref_points of the current NUMA affinity.
>>   */
>> @@ -500,17 +503,21 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>>      MachineState *ms = MACHINE(spapr);
>>      NodeInfo *numa_info = ms->numa_state->nodes;
>>      int nb_numa_nodes = ms->numa_state->num_nodes;
>> +    /* Lookup index table has an extra uint32_t with its length */
>> +    uint32_t lookup_index_table[nb_numa_nodes + 1];
>>      int distance_table_entries = nb_numa_nodes * nb_numa_nodes;
>> -    g_autofree uint32_t *lookup_index_table = NULL;
>> -    g_autofree uint32_t *distance_table = NULL;
>> -    int src, dst, i, distance_table_size;
>> -    uint8_t *node_distances;
>> +    /*
>> +     * Distance table is an uint8_t array with a leading uint32_t
>> +     * containing its length.
>> +     */
>> +    uint8_t distance_table[distance_table_entries + 4];
>> +    uint32_t *distance_table_length;
>> +    int src, dst, i;
>>
>>      /*
>>       * ibm,numa-lookup-index-table: array with length and a
>>       * list of NUMA ids present in the guest.
>>       */
>> -    lookup_index_table = g_new0(uint32_t, nb_numa_nodes + 1);
>>      lookup_index_table[0] = cpu_to_be32(nb_numa_nodes);
>>
>>      for (i = 0; i < nb_numa_nodes; i++) {
>> @@ -518,8 +525,7 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>>      }
>>
>>      _FDT(fdt_setprop(fdt, rtas, "ibm,numa-lookup-index-table",
>> -                     lookup_index_table,
>> -                     (nb_numa_nodes + 1) * sizeof(uint32_t)));
>> +                     lookup_index_table, sizeof(lookup_index_table)));
>>
>>      /*
>>       * ibm,numa-distance-table: contains all node distances. First
>> @@ -531,11 +537,10 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>>       * array because NUMA ids can be sparse (node 0 is the first,
>>       * node 8 is the second ...).
>>       */
>> -    distance_table = g_new0(uint32_t, distance_table_entries + 1);
>> -    distance_table[0] = cpu_to_be32(distance_table_entries);
>> +    distance_table_length = (uint32_t *)distance_table;
>> +    distance_table_length[0] = cpu_to_be32(distance_table_entries);
>>
>> -    node_distances = (uint8_t *)&distance_table[1];
>> -    i = 0;
>> +    i = 4;
>>
>
> A comment reminding why we're doing that wouldn't hurt, e.g.
>
> /* Skip the array size (uint32_t) */

Then maybe instead of (or in addition to) a comment you could write 
sizeof(uint32_t) or sizeof(distance_rable[0]) instead of constant 4 to 
make this more explicit.

Regards,
BALATON Zoltan

> With these fixed, especially using NUMA_DISTANCE_MIN, you
> can add:
>
> Reviewed-by: Greg Kurz <groug@kaod.org>
>
>>      for (src = 0; src < nb_numa_nodes; src++) {
>>          for (dst = 0; dst < nb_numa_nodes; dst++) {
>> @@ -546,18 +551,16 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>>               * adding the numa_info to retrieve distance info from.
>>               */
>>              if (src == dst) {
>> -                node_distances[i++] = 10;
>> +                distance_table[i++] = NUMA_LOCAL_DISTANCE;
>>                  continue;
>>              }
>>
>> -            node_distances[i++] = numa_info[src].distance[dst];
>> +            distance_table[i++] = numa_info[src].distance[dst];
>>          }
>>      }
>>
>> -    distance_table_size = distance_table_entries * sizeof(uint8_t) +
>> -                          sizeof(uint32_t);
>>      _FDT(fdt_setprop(fdt, rtas, "ibm,numa-distance-table",
>> -                     distance_table, distance_table_size));
>> +                     distance_table, sizeof(distance_table)));
>>  }
>>
>>  /*
>
>
>

Re: [PATCH] spapr_numa.c: fixes in spapr_numa_FORM2_write_rtas_tables()

[Daniel Henrique Barboza]

On 9/22/21 06:51, BALATON Zoltan wrote:
> On Wed, 22 Sep 2021, Greg Kurz wrote:
>> On Tue, 21 Sep 2021 16:43:47 -0300
>> Daniel Henrique Barboza <danielhb413@gmail.com> wrote:
>>
>>> This patch has a handful of modifications for the recent added
>>> FORM2 support:
>>>
>>> - there is no particular reason for both 'lookup_index_table' and
>>> 'distance_table' to be allocated in the heap, since their sizes are
>>> known right at the start of the function. Use static allocation in
>>> them to spare a couple of g_new0() calls;
>>>
>>> - to not allocate more than the necessary size in 'distance_table'. At
>>> this moment the array is oversized due to allocating uint32_t for all
>>> elements, when most of them fits in an uint8_t;
>>>
>>> - create a NUMA_LOCAL_DISTANCE macro to avoid hardcoding the local
>>> distance value.
>>>
>>
>> Not needed. A notion of minimal distance, which is obviously
>> synonymous to local, already exists in the "sysemu/numa.h"
>> header :
>>
>> #define NUMA_DISTANCE_MIN         10
>>
>>> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
>>> ---
>>>  hw/ppc/spapr_numa.c | 35 +++++++++++++++++++----------------
>>>  1 file changed, 19 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c
>>> index 58d5dc7084..039a0439c6 100644
>>> --- a/hw/ppc/spapr_numa.c
>>> +++ b/hw/ppc/spapr_numa.c
>>> @@ -19,6 +19,9 @@
>>>  /* Moved from hw/ppc/spapr_pci_nvlink2.c */
>>>  #define SPAPR_GPU_NUMA_ID           (cpu_to_be32(1))
>>>
>>> +/* Macro to avoid hardcoding the local distance value */
>>> +#define NUMA_LOCAL_DISTANCE         10
>>> +
>>>  /*
>>>   * Retrieves max_dist_ref_points of the current NUMA affinity.
>>>   */
>>> @@ -500,17 +503,21 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>>>      MachineState *ms = MACHINE(spapr);
>>>      NodeInfo *numa_info = ms->numa_state->nodes;
>>>      int nb_numa_nodes = ms->numa_state->num_nodes;
>>> +    /* Lookup index table has an extra uint32_t with its length */
>>> +    uint32_t lookup_index_table[nb_numa_nodes + 1];
>>>      int distance_table_entries = nb_numa_nodes * nb_numa_nodes;
>>> -    g_autofree uint32_t *lookup_index_table = NULL;
>>> -    g_autofree uint32_t *distance_table = NULL;
>>> -    int src, dst, i, distance_table_size;
>>> -    uint8_t *node_distances;
>>> +    /*
>>> +     * Distance table is an uint8_t array with a leading uint32_t
>>> +     * containing its length.
>>> +     */
>>> +    uint8_t distance_table[distance_table_entries + 4];
>>> +    uint32_t *distance_table_length;
>>> +    int src, dst, i;
>>>
>>>      /*
>>>       * ibm,numa-lookup-index-table: array with length and a
>>>       * list of NUMA ids present in the guest.
>>>       */
>>> -    lookup_index_table = g_new0(uint32_t, nb_numa_nodes + 1);
>>>      lookup_index_table[0] = cpu_to_be32(nb_numa_nodes);
>>>
>>>      for (i = 0; i < nb_numa_nodes; i++) {
>>> @@ -518,8 +525,7 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>>>      }
>>>
>>>      _FDT(fdt_setprop(fdt, rtas, "ibm,numa-lookup-index-table",
>>> -                     lookup_index_table,
>>> -                     (nb_numa_nodes + 1) * sizeof(uint32_t)));
>>> +                     lookup_index_table, sizeof(lookup_index_table)));
>>>
>>>      /*
>>>       * ibm,numa-distance-table: contains all node distances. First
>>> @@ -531,11 +537,10 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>>>       * array because NUMA ids can be sparse (node 0 is the first,
>>>       * node 8 is the second ...).
>>>       */
>>> -    distance_table = g_new0(uint32_t, distance_table_entries + 1);
>>> -    distance_table[0] = cpu_to_be32(distance_table_entries);
>>> +    distance_table_length = (uint32_t *)distance_table;
>>> +    distance_table_length[0] = cpu_to_be32(distance_table_entries);
>>>
>>> -    node_distances = (uint8_t *)&distance_table[1];
>>> -    i = 0;
>>> +    i = 4;
>>>
>>
>> A comment reminding why we're doing that wouldn't hurt, e.g.
>>
>> /* Skip the array size (uint32_t) */
> 
> Then maybe instead of (or in addition to) a comment you could write sizeof(uint32_t) or sizeof(distance_rable[0]) instead of constant 4 to make this more explicit.

distance_table is an uint8_t array. sizeof(distance_table[0]) would return 1.

Doing i = sizeof(uint32_t) demands the reader to realize "this works because it is
skipping an uint32_t in an uint8_t array and sizeof(uint8_t) is 1".

I think it's clearer to just be explicit in the comment:


/* First 4 uint8_t contains the uint32_t array length */


Thanks,


Daniel


> 
> Regards,
> BALATON Zoltan
> 
>> With these fixed, especially using NUMA_DISTANCE_MIN, you
>> can add:
>>
>> Reviewed-by: Greg Kurz <groug@kaod.org>
>>
>>>      for (src = 0; src < nb_numa_nodes; src++) {
>>>          for (dst = 0; dst < nb_numa_nodes; dst++) {
>>> @@ -546,18 +551,16 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>>>               * adding the numa_info to retrieve distance info from.
>>>               */
>>>              if (src == dst) {
>>> -                node_distances[i++] = 10;
>>> +                distance_table[i++] = NUMA_LOCAL_DISTANCE;
>>>                  continue;
>>>              }
>>>
>>> -            node_distances[i++] = numa_info[src].distance[dst];
>>> +            distance_table[i++] = numa_info[src].distance[dst];
>>>          }
>>>      }
>>>
>>> -    distance_table_size = distance_table_entries * sizeof(uint8_t) +
>>> -                          sizeof(uint32_t);
>>>      _FDT(fdt_setprop(fdt, rtas, "ibm,numa-distance-table",
>>> -                     distance_table, distance_table_size));
>>> +                     distance_table, sizeof(distance_table)));
>>>  }
>>>
>>>  /*
>>
>>
>>

Re: [PATCH] spapr_numa.c: fixes in spapr_numa_FORM2_write_rtas_tables()

[BALATON Zoltan]

[-- Attachment #1: Type: text/plain, Size: 5527 bytes --]

On Wed, 22 Sep 2021, Daniel Henrique Barboza wrote:
> On 9/22/21 06:51, BALATON Zoltan wrote:
>> On Wed, 22 Sep 2021, Greg Kurz wrote:
>>> On Tue, 21 Sep 2021 16:43:47 -0300
>>> Daniel Henrique Barboza <danielhb413@gmail.com> wrote:
>>> 
>>>> This patch has a handful of modifications for the recent added
>>>> FORM2 support:
>>>> 
>>>> - there is no particular reason for both 'lookup_index_table' and
>>>> 'distance_table' to be allocated in the heap, since their sizes are
>>>> known right at the start of the function. Use static allocation in
>>>> them to spare a couple of g_new0() calls;
>>>> 
>>>> - to not allocate more than the necessary size in 'distance_table'. At
>>>> this moment the array is oversized due to allocating uint32_t for all
>>>> elements, when most of them fits in an uint8_t;
>>>> 
>>>> - create a NUMA_LOCAL_DISTANCE macro to avoid hardcoding the local
>>>> distance value.
>>>> 
>>> 
>>> Not needed. A notion of minimal distance, which is obviously
>>> synonymous to local, already exists in the "sysemu/numa.h"
>>> header :
>>> 
>>> #define NUMA_DISTANCE_MIN         10
>>> 
>>>> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
>>>> ---
>>>>  hw/ppc/spapr_numa.c | 35 +++++++++++++++++++----------------
>>>>  1 file changed, 19 insertions(+), 16 deletions(-)
>>>> 
>>>> diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c
>>>> index 58d5dc7084..039a0439c6 100644
>>>> --- a/hw/ppc/spapr_numa.c
>>>> +++ b/hw/ppc/spapr_numa.c
>>>> @@ -19,6 +19,9 @@
>>>>  /* Moved from hw/ppc/spapr_pci_nvlink2.c */
>>>>  #define SPAPR_GPU_NUMA_ID           (cpu_to_be32(1))
>>>> 
>>>> +/* Macro to avoid hardcoding the local distance value */
>>>> +#define NUMA_LOCAL_DISTANCE         10
>>>> +
>>>>  /*
>>>>   * Retrieves max_dist_ref_points of the current NUMA affinity.
>>>>   */
>>>> @@ -500,17 +503,21 @@ static void 
>>>> spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>>>>      MachineState *ms = MACHINE(spapr);
>>>>      NodeInfo *numa_info = ms->numa_state->nodes;
>>>>      int nb_numa_nodes = ms->numa_state->num_nodes;
>>>> +    /* Lookup index table has an extra uint32_t with its length */
>>>> +    uint32_t lookup_index_table[nb_numa_nodes + 1];
>>>>      int distance_table_entries = nb_numa_nodes * nb_numa_nodes;
>>>> -    g_autofree uint32_t *lookup_index_table = NULL;
>>>> -    g_autofree uint32_t *distance_table = NULL;
>>>> -    int src, dst, i, distance_table_size;
>>>> -    uint8_t *node_distances;
>>>> +    /*
>>>> +     * Distance table is an uint8_t array with a leading uint32_t
>>>> +     * containing its length.
>>>> +     */
>>>> +    uint8_t distance_table[distance_table_entries + 4];
>>>> +    uint32_t *distance_table_length;
>>>> +    int src, dst, i;
>>>> 
>>>>      /*
>>>>       * ibm,numa-lookup-index-table: array with length and a
>>>>       * list of NUMA ids present in the guest.
>>>>       */
>>>> -    lookup_index_table = g_new0(uint32_t, nb_numa_nodes + 1);
>>>>      lookup_index_table[0] = cpu_to_be32(nb_numa_nodes);
>>>> 
>>>>      for (i = 0; i < nb_numa_nodes; i++) {
>>>> @@ -518,8 +525,7 @@ static void 
>>>> spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>>>>      }
>>>> 
>>>>      _FDT(fdt_setprop(fdt, rtas, "ibm,numa-lookup-index-table",
>>>> -                     lookup_index_table,
>>>> -                     (nb_numa_nodes + 1) * sizeof(uint32_t)));
>>>> +                     lookup_index_table, sizeof(lookup_index_table)));
>>>> 
>>>>      /*
>>>>       * ibm,numa-distance-table: contains all node distances. First
>>>> @@ -531,11 +537,10 @@ static void 
>>>> spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>>>>       * array because NUMA ids can be sparse (node 0 is the first,
>>>>       * node 8 is the second ...).
>>>>       */
>>>> -    distance_table = g_new0(uint32_t, distance_table_entries + 1);
>>>> -    distance_table[0] = cpu_to_be32(distance_table_entries);
>>>> +    distance_table_length = (uint32_t *)distance_table;
>>>> +    distance_table_length[0] = cpu_to_be32(distance_table_entries);
>>>> 
>>>> -    node_distances = (uint8_t *)&distance_table[1];
>>>> -    i = 0;
>>>> +    i = 4;
>>>> 
>>> 
>>> A comment reminding why we're doing that wouldn't hurt, e.g.
>>> 
>>> /* Skip the array size (uint32_t) */
>> 
>> Then maybe instead of (or in addition to) a comment you could write 
>> sizeof(uint32_t) or sizeof(distance_rable[0]) instead of constant 4 to make 
>> this more explicit.
>
> distance_table is an uint8_t array. sizeof(distance_table[0]) would return 1.

Yes, sorry I was looking at uint32_t *distance_table_length; instead of 
the array definition.

> Doing i = sizeof(uint32_t) demands the reader to realize "this works because 
> it is
> skipping an uint32_t in an uint8_t array and sizeof(uint8_t) is 1".
>
> I think it's clearer to just be explicit in the comment:
>
>
> /* First 4 uint8_t contains the uint32_t array length */

That explains it better (although a bit confusing, if you need the length 
why don't you have a struct with the length and the array instead of 
sroring it in the array when that's a different type, unless this is some 
data structure defined that way, I don't know what this is all about). But 
I don't really care, adding this comment is fine.

Regards,
BALATON Zoltan

Re: [PATCH] spapr_numa.c: fixes in spapr_numa_FORM2_write_rtas_tables()

[Philippe Mathieu-Daudé]

On 9/21/21 21:43, Daniel Henrique Barboza wrote:
> This patch has a handful of modifications for the recent added
> FORM2 support:
> 
> - there is no particular reason for both 'lookup_index_table' and
> 'distance_table' to be allocated in the heap, since their sizes are
> known right at the start of the function. Use static allocation in
> them to spare a couple of g_new0() calls;
> 
> - to not allocate more than the necessary size in 'distance_table'. At
> this moment the array is oversized due to allocating uint32_t for all
> elements, when most of them fits in an uint8_t;
> 
> - create a NUMA_LOCAL_DISTANCE macro to avoid hardcoding the local
> distance value.
> 
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> ---
>   hw/ppc/spapr_numa.c | 35 +++++++++++++++++++----------------
>   1 file changed, 19 insertions(+), 16 deletions(-)
> 
> diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c
> index 58d5dc7084..039a0439c6 100644
> --- a/hw/ppc/spapr_numa.c
> +++ b/hw/ppc/spapr_numa.c
> @@ -19,6 +19,9 @@
>   /* Moved from hw/ppc/spapr_pci_nvlink2.c */
>   #define SPAPR_GPU_NUMA_ID           (cpu_to_be32(1))
>   
> +/* Macro to avoid hardcoding the local distance value */
> +#define NUMA_LOCAL_DISTANCE         10
> +
>   /*
>    * Retrieves max_dist_ref_points of the current NUMA affinity.
>    */
> @@ -500,17 +503,21 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>       MachineState *ms = MACHINE(spapr);
>       NodeInfo *numa_info = ms->numa_state->nodes;
>       int nb_numa_nodes = ms->numa_state->num_nodes;
> +    /* Lookup index table has an extra uint32_t with its length */
> +    uint32_t lookup_index_table[nb_numa_nodes + 1];
>       int distance_table_entries = nb_numa_nodes * nb_numa_nodes;
> -    g_autofree uint32_t *lookup_index_table = NULL;
> -    g_autofree uint32_t *distance_table = NULL;
> -    int src, dst, i, distance_table_size;
> -    uint8_t *node_distances;

This should have be of ptrdiff_t type.

> +    /*
> +     * Distance table is an uint8_t array with a leading uint32_t
> +     * containing its length.
> +     */
> +    uint8_t distance_table[distance_table_entries + 4];

The previous code seems better by using the heap, now we have
to worry about stack overflow...

> +    uint32_t *distance_table_length;

Please drop, ...

> +    int src, dst, i;
>   
>       /*
>        * ibm,numa-lookup-index-table: array with length and a
>        * list of NUMA ids present in the guest.
>        */
> -    lookup_index_table = g_new0(uint32_t, nb_numa_nodes + 1);
>       lookup_index_table[0] = cpu_to_be32(nb_numa_nodes);
>   
>       for (i = 0; i < nb_numa_nodes; i++) {
> @@ -518,8 +525,7 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>       }
>   
>       _FDT(fdt_setprop(fdt, rtas, "ibm,numa-lookup-index-table",
> -                     lookup_index_table,
> -                     (nb_numa_nodes + 1) * sizeof(uint32_t)));
> +                     lookup_index_table, sizeof(lookup_index_table)));
>   
>       /*
>        * ibm,numa-distance-table: contains all node distances. First
> @@ -531,11 +537,10 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>        * array because NUMA ids can be sparse (node 0 is the first,
>        * node 8 is the second ...).
>        */
> -    distance_table = g_new0(uint32_t, distance_table_entries + 1);
> -    distance_table[0] = cpu_to_be32(distance_table_entries);
> +    distance_table_length = (uint32_t *)distance_table;
> +    distance_table_length[0] = cpu_to_be32(distance_table_entries);

... and use instead:

        stl_be_p(distance_table, distance_table_entries);

> -    node_distances = (uint8_t *)&distance_table[1];
> -    i = 0;
> +    i = 4;
>   
>       for (src = 0; src < nb_numa_nodes; src++) {
>           for (dst = 0; dst < nb_numa_nodes; dst++) {
> @@ -546,18 +551,16 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>                * adding the numa_info to retrieve distance info from.
>                */
>               if (src == dst) {
> -                node_distances[i++] = 10;
> +                distance_table[i++] = NUMA_LOCAL_DISTANCE;
>                   continue;
>               }
>   
> -            node_distances[i++] = numa_info[src].distance[dst];
> +            distance_table[i++] = numa_info[src].distance[dst];
>           }
>       }
>   
> -    distance_table_size = distance_table_entries * sizeof(uint8_t) +
> -                          sizeof(uint32_t);
>       _FDT(fdt_setprop(fdt, rtas, "ibm,numa-distance-table",
> -                     distance_table, distance_table_size));
> +                     distance_table, sizeof(distance_table)));
>   }
>   
>   /*
> 

Re: [PATCH] spapr_numa.c: fixes in spapr_numa_FORM2_write_rtas_tables()

[Daniel Henrique Barboza]

On 9/22/21 08:17, Philippe Mathieu-Daudé wrote:
> On 9/21/21 21:43, Daniel Henrique Barboza wrote:
>> This patch has a handful of modifications for the recent added
>> FORM2 support:
>>
>> - there is no particular reason for both 'lookup_index_table' and
>> 'distance_table' to be allocated in the heap, since their sizes are
>> known right at the start of the function. Use static allocation in
>> them to spare a couple of g_new0() calls;
>>
>> - to not allocate more than the necessary size in 'distance_table'. At
>> this moment the array is oversized due to allocating uint32_t for all
>> elements, when most of them fits in an uint8_t;
>>
>> - create a NUMA_LOCAL_DISTANCE macro to avoid hardcoding the local
>> distance value.
>>
>> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
>> ---
>>   hw/ppc/spapr_numa.c | 35 +++++++++++++++++++----------------
>>   1 file changed, 19 insertions(+), 16 deletions(-)
>>
>> diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c
>> index 58d5dc7084..039a0439c6 100644
>> --- a/hw/ppc/spapr_numa.c
>> +++ b/hw/ppc/spapr_numa.c
>> @@ -19,6 +19,9 @@
>>   /* Moved from hw/ppc/spapr_pci_nvlink2.c */
>>   #define SPAPR_GPU_NUMA_ID           (cpu_to_be32(1))
>> +/* Macro to avoid hardcoding the local distance value */
>> +#define NUMA_LOCAL_DISTANCE         10
>> +
>>   /*
>>    * Retrieves max_dist_ref_points of the current NUMA affinity.
>>    */
>> @@ -500,17 +503,21 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>>       MachineState *ms = MACHINE(spapr);
>>       NodeInfo *numa_info = ms->numa_state->nodes;
>>       int nb_numa_nodes = ms->numa_state->num_nodes;
>> +    /* Lookup index table has an extra uint32_t with its length */
>> +    uint32_t lookup_index_table[nb_numa_nodes + 1];
>>       int distance_table_entries = nb_numa_nodes * nb_numa_nodes;
>> -    g_autofree uint32_t *lookup_index_table = NULL;
>> -    g_autofree uint32_t *distance_table = NULL;
>> -    int src, dst, i, distance_table_size;
>> -    uint8_t *node_distances;
> 
> This should have be of ptrdiff_t type.
> 
>> +    /*
>> +     * Distance table is an uint8_t array with a leading uint32_t
>> +     * containing its length.
>> +     */
>> +    uint8_t distance_table[distance_table_entries + 4];
> 
> The previous code seems better by using the heap, now we have
> to worry about stack overflow...


Fair point.

Since no one asked for this change in previous reviews I guess it's fine to keep
using the heap.


Daniel


> 
>> +    uint32_t *distance_table_length;
> 
> Please drop, ...
> 
>> +    int src, dst, i;
>>       /*
>>        * ibm,numa-lookup-index-table: array with length and a
>>        * list of NUMA ids present in the guest.
>>        */
>> -    lookup_index_table = g_new0(uint32_t, nb_numa_nodes + 1);
>>       lookup_index_table[0] = cpu_to_be32(nb_numa_nodes);
>>       for (i = 0; i < nb_numa_nodes; i++) {
>> @@ -518,8 +525,7 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>>       }
>>       _FDT(fdt_setprop(fdt, rtas, "ibm,numa-lookup-index-table",
>> -                     lookup_index_table,
>> -                     (nb_numa_nodes + 1) * sizeof(uint32_t)));
>> +                     lookup_index_table, sizeof(lookup_index_table)));
>>       /*
>>        * ibm,numa-distance-table: contains all node distances. First
>> @@ -531,11 +537,10 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>>        * array because NUMA ids can be sparse (node 0 is the first,
>>        * node 8 is the second ...).
>>        */
>> -    distance_table = g_new0(uint32_t, distance_table_entries + 1);
>> -    distance_table[0] = cpu_to_be32(distance_table_entries);
>> +    distance_table_length = (uint32_t *)distance_table;
>> +    distance_table_length[0] = cpu_to_be32(distance_table_entries);
> 
> ... and use instead:
> 
>         stl_be_p(distance_table, distance_table_entries);
> 
>> -    node_distances = (uint8_t *)&distance_table[1];
>> -    i = 0;
>> +    i = 4;
>>       for (src = 0; src < nb_numa_nodes; src++) {
>>           for (dst = 0; dst < nb_numa_nodes; dst++) {
>> @@ -546,18 +551,16 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>>                * adding the numa_info to retrieve distance info from.
>>                */
>>               if (src == dst) {
>> -                node_distances[i++] = 10;
>> +                distance_table[i++] = NUMA_LOCAL_DISTANCE;
>>                   continue;
>>               }
>> -            node_distances[i++] = numa_info[src].distance[dst];
>> +            distance_table[i++] = numa_info[src].distance[dst];
>>           }
>>       }
>> -    distance_table_size = distance_table_entries * sizeof(uint8_t) +
>> -                          sizeof(uint32_t);
>>       _FDT(fdt_setprop(fdt, rtas, "ibm,numa-distance-table",
>> -                     distance_table, distance_table_size));
>> +                     distance_table, sizeof(distance_table)));
>>   }
>>   /*
>>
> 

Re: [PATCH] spapr_numa.c: fixes in spapr_numa_FORM2_write_rtas_tables()

[Greg Kurz]

On Wed, 22 Sep 2021 13:17:32 +0200
Philippe Mathieu-Daudé <philmd@redhat.com> wrote:

> On 9/21/21 21:43, Daniel Henrique Barboza wrote:
> > This patch has a handful of modifications for the recent added
> > FORM2 support:
> > 
> > - there is no particular reason for both 'lookup_index_table' and
> > 'distance_table' to be allocated in the heap, since their sizes are
> > known right at the start of the function. Use static allocation in
> > them to spare a couple of g_new0() calls;
> > 
> > - to not allocate more than the necessary size in 'distance_table'. At
> > this moment the array is oversized due to allocating uint32_t for all
> > elements, when most of them fits in an uint8_t;
> > 
> > - create a NUMA_LOCAL_DISTANCE macro to avoid hardcoding the local
> > distance value.
> > 
> > Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> > ---
> >   hw/ppc/spapr_numa.c | 35 +++++++++++++++++++----------------
> >   1 file changed, 19 insertions(+), 16 deletions(-)
> > 
> > diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c
> > index 58d5dc7084..039a0439c6 100644
> > --- a/hw/ppc/spapr_numa.c
> > +++ b/hw/ppc/spapr_numa.c
> > @@ -19,6 +19,9 @@
> >   /* Moved from hw/ppc/spapr_pci_nvlink2.c */
> >   #define SPAPR_GPU_NUMA_ID           (cpu_to_be32(1))
> >   
> > +/* Macro to avoid hardcoding the local distance value */
> > +#define NUMA_LOCAL_DISTANCE         10
> > +
> >   /*
> >    * Retrieves max_dist_ref_points of the current NUMA affinity.
> >    */
> > @@ -500,17 +503,21 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
> >       MachineState *ms = MACHINE(spapr);
> >       NodeInfo *numa_info = ms->numa_state->nodes;
> >       int nb_numa_nodes = ms->numa_state->num_nodes;
> > +    /* Lookup index table has an extra uint32_t with its length */
> > +    uint32_t lookup_index_table[nb_numa_nodes + 1];
> >       int distance_table_entries = nb_numa_nodes * nb_numa_nodes;
> > -    g_autofree uint32_t *lookup_index_table = NULL;
> > -    g_autofree uint32_t *distance_table = NULL;
> > -    int src, dst, i, distance_table_size;
> > -    uint8_t *node_distances;
> 
> This should have be of ptrdiff_t type.
> 

Why ? I don't see pointer subtraction in the code.

> > +    /*
> > +     * Distance table is an uint8_t array with a leading uint32_t
> > +     * containing its length.
> > +     */
> > +    uint8_t distance_table[distance_table_entries + 4];
> 
> The previous code seems better by using the heap, now we have
> to worry about stack overflow...
> 

Indeed the size of this array could be up to 16k + 4. I guess
Philippe's point make sense. David's request was to use uint8_t
instead of uin32t_t, not to drop g_new0(). Please revert to
using the heap.

lookup_index_table[] can _only_ grow up to 516 bytes, which is
less problematic, but it doesn't hurt either to allocate it
on the heap. Not changing that would make this patch simpler.

> > +    uint32_t *distance_table_length;
> 
> Please drop, ...
> 
> > +    int src, dst, i;
> >   
> >       /*
> >        * ibm,numa-lookup-index-table: array with length and a
> >        * list of NUMA ids present in the guest.
> >        */
> > -    lookup_index_table = g_new0(uint32_t, nb_numa_nodes + 1);
> >       lookup_index_table[0] = cpu_to_be32(nb_numa_nodes);
> >   
> >       for (i = 0; i < nb_numa_nodes; i++) {
> > @@ -518,8 +525,7 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
> >       }
> >   
> >       _FDT(fdt_setprop(fdt, rtas, "ibm,numa-lookup-index-table",
> > -                     lookup_index_table,
> > -                     (nb_numa_nodes + 1) * sizeof(uint32_t)));
> > +                     lookup_index_table, sizeof(lookup_index_table)));
> >   
> >       /*
> >        * ibm,numa-distance-table: contains all node distances. First
> > @@ -531,11 +537,10 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
> >        * array because NUMA ids can be sparse (node 0 is the first,
> >        * node 8 is the second ...).
> >        */
> > -    distance_table = g_new0(uint32_t, distance_table_entries + 1);
> > -    distance_table[0] = cpu_to_be32(distance_table_entries);
> > +    distance_table_length = (uint32_t *)distance_table;
> > +    distance_table_length[0] = cpu_to_be32(distance_table_entries);
> 
> ... and use instead:
> 
>         stl_be_p(distance_table, distance_table_entries);
> 

+1

> > -    node_distances = (uint8_t *)&distance_table[1];
> > -    i = 0;
> > +    i = 4;
> >   
> >       for (src = 0; src < nb_numa_nodes; src++) {
> >           for (dst = 0; dst < nb_numa_nodes; dst++) {
> > @@ -546,18 +551,16 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
> >                * adding the numa_info to retrieve distance info from.
> >                */
> >               if (src == dst) {
> > -                node_distances[i++] = 10;
> > +                distance_table[i++] = NUMA_LOCAL_DISTANCE;
> >                   continue;
> >               }
> >   
> > -            node_distances[i++] = numa_info[src].distance[dst];
> > +            distance_table[i++] = numa_info[src].distance[dst];
> >           }
> >       }
> >   
> > -    distance_table_size = distance_table_entries * sizeof(uint8_t) +
> > -                          sizeof(uint32_t);
> >       _FDT(fdt_setprop(fdt, rtas, "ibm,numa-distance-table",
> > -                     distance_table, distance_table_size));
> > +                     distance_table, sizeof(distance_table)));
> >   }
> >   
> >   /*
> > 
> 

Re: [PATCH] spapr_numa.c: fixes in spapr_numa_FORM2_write_rtas_tables()

[Philippe Mathieu-Daudé]

On 9/22/21 13:52, Greg Kurz wrote:
> On Wed, 22 Sep 2021 13:17:32 +0200
> Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
> 
>> On 9/21/21 21:43, Daniel Henrique Barboza wrote:
>>> This patch has a handful of modifications for the recent added
>>> FORM2 support:
>>>
>>> - there is no particular reason for both 'lookup_index_table' and
>>> 'distance_table' to be allocated in the heap, since their sizes are
>>> known right at the start of the function. Use static allocation in
>>> them to spare a couple of g_new0() calls;
>>>
>>> - to not allocate more than the necessary size in 'distance_table'. At
>>> this moment the array is oversized due to allocating uint32_t for all
>>> elements, when most of them fits in an uint8_t;
>>>
>>> - create a NUMA_LOCAL_DISTANCE macro to avoid hardcoding the local
>>> distance value.
>>>
>>> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
>>> ---
>>>    hw/ppc/spapr_numa.c | 35 +++++++++++++++++++----------------
>>>    1 file changed, 19 insertions(+), 16 deletions(-)

>>>    /*
>>>     * Retrieves max_dist_ref_points of the current NUMA affinity.
>>>     */
>>> @@ -500,17 +503,21 @@ static void spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
>>>        MachineState *ms = MACHINE(spapr);
>>>        NodeInfo *numa_info = ms->numa_state->nodes;
>>>        int nb_numa_nodes = ms->numa_state->num_nodes;
>>> +    /* Lookup index table has an extra uint32_t with its length */
>>> +    uint32_t lookup_index_table[nb_numa_nodes + 1];
>>>        int distance_table_entries = nb_numa_nodes * nb_numa_nodes;
>>> -    g_autofree uint32_t *lookup_index_table = NULL;
>>> -    g_autofree uint32_t *distance_table = NULL;
>>> -    int src, dst, i, distance_table_size;
>>> -    uint8_t *node_distances;
>>
>> This should have be of ptrdiff_t type.
>>
> 
> Why ? I don't see pointer subtraction in the code.

Oops, you are right.