[v6,18/18] spapr: Fold spapr_node0_size() into its only caller
diff mbox series

Message ID 20200224233724.46415-19-david@gibson.dropbear.id.au
State New
Headers show
Series
  • [v6,01/18] pseries: Update SLOF firmware image
Related show

Commit Message

David Gibson Feb. 24, 2020, 11:37 p.m. UTC
The Real Mode Area (RMA) needs to fit within the NUMA node owning memory
at address 0.  That's usually node 0, but can be a later one if there are
some nodes which have no memory (only CPUs).

This is currently handled by the spapr_node0_size() helper.  It has only
one caller, so there's not a lot of point splitting it out.  It's also
extremely easy to misread the code as clamping to the size of the smallest
node rather than the first node with any memory.

So, fold it into the caller, and add some commentary to make it a bit
clearer exactly what it's doing.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 hw/ppc/spapr.c | 37 +++++++++++++++++++++----------------
 1 file changed, 21 insertions(+), 16 deletions(-)

Comments

Greg Kurz Feb. 26, 2020, 2:47 p.m. UTC | #1
On Tue, 25 Feb 2020 10:37:24 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> The Real Mode Area (RMA) needs to fit within the NUMA node owning memory
> at address 0.  That's usually node 0, but can be a later one if there are
> some nodes which have no memory (only CPUs).
> 
> This is currently handled by the spapr_node0_size() helper.  It has only
> one caller, so there's not a lot of point splitting it out.  It's also
> extremely easy to misread the code as clamping to the size of the smallest
> node rather than the first node with any memory.
> 
> So, fold it into the caller, and add some commentary to make it a bit
> clearer exactly what it's doing.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  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 f0354b699d..9ba645c9cb 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -296,20 +296,6 @@ static void spapr_populate_pa_features(SpaprMachineState *spapr,
>      _FDT((fdt_setprop(fdt, offset, "ibm,pa-features", pa_features, pa_size)));
>  }
>  
> -static hwaddr spapr_node0_size(MachineState *machine)
> -{
> -    if (machine->numa_state->num_nodes) {
> -        int i;
> -        for (i = 0; i < machine->numa_state->num_nodes; ++i) {
> -            if (machine->numa_state->nodes[i].node_mem) {
> -                return MIN(pow2floor(machine->numa_state->nodes[i].node_mem),
> -                           machine->ram_size);
> -            }
> -        }
> -    }
> -    return machine->ram_size;
> -}
> -
>  static void add_str(GString *s, const gchar *s1)
>  {
>      g_string_append_len(s, s1, strlen(s1) + 1);
> @@ -2652,10 +2638,24 @@ static hwaddr spapr_rma_size(SpaprMachineState *spapr, Error **errp)
>  {
>      MachineState *machine = MACHINE(spapr);
>      hwaddr rma_size = machine->ram_size;
> -    hwaddr node0_size = spapr_node0_size(machine);
>  
>      /* RMA has to fit in the first NUMA node */
> -    rma_size = MIN(rma_size, node0_size);
> +    if (machine->numa_state->num_nodes) {
> +        /*
> +         * It's possible for there to be some zero-memory nodes first
> +         * in the list.  We need the RMA to fit inside the memory of
> +         * the first node which actually has some memory.
> +         */
> +        int i;
> +
> +        for (i = 0; i < machine->numa_state->num_nodes; ++i) {
> +            if (machine->numa_state->nodes[i].node_mem != 0) {
> +                rma_size = MIN(rma_size,
> +                               machine->numa_state->nodes[i].node_mem);
> +                break;
> +            }
> +        }
> +    }
>  
>      /*
>       * VRMA access is via a special 1TiB SLB mapping, so the RMA can
> @@ -2672,6 +2672,11 @@ static hwaddr spapr_rma_size(SpaprMachineState *spapr, Error **errp)
>          spapr->rma_size = MIN(spapr->rma_size, smc->rma_limit);
>      }
>  
> +    /*
> +     * RMA size must be a power of 2
> +     */
> +    rma_size = pow2floor(rma_size);
> +

This slightly changes semantics. In a scenario without NUMA,
we used to get:

    rma_size == machine->ram_size

but with this patch we now get:

    rma_size == pow2floor(machine->ram_size)

Maybe mention it in the changelog ?

Anyway,

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

>      if (rma_size < (MIN_RMA_SLOF * MiB)) {
>          error_setg(errp,
>  "pSeries SLOF firmware requires >= %ldMiB guest RMA (Real Mode Area)",

Patch
diff mbox series

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index f0354b699d..9ba645c9cb 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -296,20 +296,6 @@  static void spapr_populate_pa_features(SpaprMachineState *spapr,
     _FDT((fdt_setprop(fdt, offset, "ibm,pa-features", pa_features, pa_size)));
 }
 
-static hwaddr spapr_node0_size(MachineState *machine)
-{
-    if (machine->numa_state->num_nodes) {
-        int i;
-        for (i = 0; i < machine->numa_state->num_nodes; ++i) {
-            if (machine->numa_state->nodes[i].node_mem) {
-                return MIN(pow2floor(machine->numa_state->nodes[i].node_mem),
-                           machine->ram_size);
-            }
-        }
-    }
-    return machine->ram_size;
-}
-
 static void add_str(GString *s, const gchar *s1)
 {
     g_string_append_len(s, s1, strlen(s1) + 1);
@@ -2652,10 +2638,24 @@  static hwaddr spapr_rma_size(SpaprMachineState *spapr, Error **errp)
 {
     MachineState *machine = MACHINE(spapr);
     hwaddr rma_size = machine->ram_size;
-    hwaddr node0_size = spapr_node0_size(machine);
 
     /* RMA has to fit in the first NUMA node */
-    rma_size = MIN(rma_size, node0_size);
+    if (machine->numa_state->num_nodes) {
+        /*
+         * It's possible for there to be some zero-memory nodes first
+         * in the list.  We need the RMA to fit inside the memory of
+         * the first node which actually has some memory.
+         */
+        int i;
+
+        for (i = 0; i < machine->numa_state->num_nodes; ++i) {
+            if (machine->numa_state->nodes[i].node_mem != 0) {
+                rma_size = MIN(rma_size,
+                               machine->numa_state->nodes[i].node_mem);
+                break;
+            }
+        }
+    }
 
     /*
      * VRMA access is via a special 1TiB SLB mapping, so the RMA can
@@ -2672,6 +2672,11 @@  static hwaddr spapr_rma_size(SpaprMachineState *spapr, Error **errp)
         spapr->rma_size = MIN(spapr->rma_size, smc->rma_limit);
     }
 
+    /*
+     * RMA size must be a power of 2
+     */
+    rma_size = pow2floor(rma_size);
+
     if (rma_size < (MIN_RMA_SLOF * MiB)) {
         error_setg(errp,
 "pSeries SLOF firmware requires >= %ldMiB guest RMA (Real Mode Area)",