The smmu_find_smmu_pcibus() function was introduced (in commit
cac994ef43b) in a code format that could return an incorrect
pointer, which was then fixed by the previous commit.
We could have avoid this by writing the if() statement differently.
Do it now, in case this function is re-used. The code is easier to
review (harder to miss bugs).

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
This patch is easier to review with 'git-diff -w' (--ignore-all-space)
---
 hw/arm/smmu-common.c | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/hw/arm/smmu-common.c b/hw/arm/smmu-common.c
index 67d7b2d0fd..e13a5f4a7c 100644
--- a/hw/arm/smmu-common.c
+++ b/hw/arm/smmu-common.c
@@ -290,20 +290,21 @@ inline int smmu_ptw(SMMUTransCfg *cfg, dma_addr_t iova, IOMMUAccessFlags perm,
 SMMUPciBus *smmu_find_smmu_pcibus(SMMUState *s, uint8_t bus_num)
 {
     SMMUPciBus *smmu_pci_bus = s->smmu_pcibus_by_bus_num[bus_num];
+    GHashTableIter iter;
 
-    if (!smmu_pci_bus) {
-        GHashTableIter iter;
-
-        g_hash_table_iter_init(&iter, s->smmu_pcibus_by_busptr);
-        while (g_hash_table_iter_next(&iter, NULL, (void **)&smmu_pci_bus)) {
-            if (pci_bus_num(smmu_pci_bus->bus) == bus_num) {
-                s->smmu_pcibus_by_bus_num[bus_num] = smmu_pci_bus;
-                return smmu_pci_bus;
-            }
-        }
-        smmu_pci_bus = NULL;
+    if (smmu_pci_bus) {
+        return smmu_pci_bus;
     }
-    return smmu_pci_bus;
+
+    g_hash_table_iter_init(&iter, s->smmu_pcibus_by_busptr);
+    while (g_hash_table_iter_next(&iter, NULL, (void **)&smmu_pci_bus)) {
+        if (pci_bus_num(smmu_pci_bus->bus) == bus_num) {
+            s->smmu_pcibus_by_bus_num[bus_num] = smmu_pci_bus;
+            return smmu_pci_bus;
+        }
+    }
+
+    return NULL;
 }
 
 static AddressSpace *smmu_find_add_as(PCIBus *bus, void *opaque, int devfn)
-- 
2.21.1

Hi Philippe,
On 2/27/20 8:51 AM, Philippe Mathieu-Daudé wrote:
> The smmu_find_smmu_pcibus() function was introduced (in commit
> cac994ef43b) in a code format that could return an incorrect
> pointer, which was then fixed by the previous commit.
> We could have avoid this by writing the if() statement differently.
nit: avoided
> Do it now, in case this function is re-used. The code is easier to
> review (harder to miss bugs).
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
> This patch is easier to review with 'git-diff -w' (--ignore-all-space)
> ---
>  hw/arm/smmu-common.c | 25 +++++++++++++------------
>  1 file changed, 13 insertions(+), 12 deletions(-)
> 
> diff --git a/hw/arm/smmu-common.c b/hw/arm/smmu-common.c
> index 67d7b2d0fd..e13a5f4a7c 100644
> --- a/hw/arm/smmu-common.c
> +++ b/hw/arm/smmu-common.c
> @@ -290,20 +290,21 @@ inline int smmu_ptw(SMMUTransCfg *cfg, dma_addr_t iova, IOMMUAccessFlags perm,
>  SMMUPciBus *smmu_find_smmu_pcibus(SMMUState *s, uint8_t bus_num)
>  {
>      SMMUPciBus *smmu_pci_bus = s->smmu_pcibus_by_bus_num[bus_num];
> +    GHashTableIter iter;
>  
> -    if (!smmu_pci_bus) {
> -        GHashTableIter iter;
> -
> -        g_hash_table_iter_init(&iter, s->smmu_pcibus_by_busptr);
> -        while (g_hash_table_iter_next(&iter, NULL, (void **)&smmu_pci_bus)) {
> -            if (pci_bus_num(smmu_pci_bus->bus) == bus_num) {
> -                s->smmu_pcibus_by_bus_num[bus_num] = smmu_pci_bus;
> -                return smmu_pci_bus;
> -            }
> -        }
> -        smmu_pci_bus = NULL;
> +    if (smmu_pci_bus) {
> +        return smmu_pci_bus;
>      }
> -    return smmu_pci_bus;
> +
> +    g_hash_table_iter_init(&iter, s->smmu_pcibus_by_busptr);
> +    while (g_hash_table_iter_next(&iter, NULL, (void **)&smmu_pci_bus)) {
> +        if (pci_bus_num(smmu_pci_bus->bus) == bus_num) {
> +            s->smmu_pcibus_by_bus_num[bus_num] = smmu_pci_bus;
> +            return smmu_pci_bus;
> +        }
> +    }
> +
> +    return NULL;
>  }
>  
>  static AddressSpace *smmu_find_add_as(PCIBus *bus, void *opaque, int devfn)
> 
Acked-by: Eric Auger <eric.auger@redhat.com>

Thanks!

Eric

On Thu, Feb 27, 2020 at 08:51:11AM +0100, Philippe Mathieu-Daudé wrote:
> The smmu_find_smmu_pcibus() function was introduced (in commit
> cac994ef43b) in a code format that could return an incorrect
> pointer, which was then fixed by the previous commit.
> We could have avoid this by writing the if() statement differently.
> Do it now, in case this function is re-used. The code is easier to
> review (harder to miss bugs).
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Reviewed-by: Peter Xu <peterx@redhat.com>

-- 
Peter Xu