[Qemu-devel] [PATCH] pci: fix pci_find_bus().

[Qemu-devel] [PATCH] pci: fix pci_find_bus().

[Isaku Yamahata]

When looking down child bus, it looked parent bridge's
bus number.
It should look child bridge's.

Cc: Blue Swirl <blauwirbel@gmail.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
---
 hw/pci.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/pci.c b/hw/pci.c
index 0dbca17..2f6907b 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -1557,9 +1557,9 @@ PCIBus *pci_find_bus(PCIBus *bus, int bus_num)
 
     /* try child bus */
     QLIST_FOREACH(sec, &bus->child, sibling) {
-        if (!bus->parent_dev /* pci host bridge */
+        if (!sec->parent_dev /* pci host bridge */
             || (pci_bus_num(sec) <= bus_num &&
-                bus_num <= bus->parent_dev->config[PCI_SUBORDINATE_BUS]) ) {
+                bus_num <= sec->parent_dev->config[PCI_SUBORDINATE_BUS]) ) {
             ret = pci_find_bus(sec, bus_num);
             if (ret) {
                 return ret;
-- 
1.6.6.1

[Qemu-devel] Re: [PATCH] pci: fix pci_find_bus().

[Isaku Yamahata]

Oh I sent out the wrong one. This is the correct one.
Sorry for noise.

>From 370c23c837070f78ca5715f032eacbf6747d42fb Mon Sep 17 00:00:00 2001
Message-Id: <370c23c837070f78ca5715f032eacbf6747d42fb.1270856742.git.yamahata@valinux.co.jp>
In-Reply-To: <cover.1270856742.git.yamahata@valinux.co.jp>
References: <cover.1270856742.git.yamahata@valinux.co.jp>
From: Isaku Yamahata <yamahata@valinux.co.jp>
Date: Fri, 9 Apr 2010 19:09:35 +0900
Subject: [PATCH] pci: fix pci_find_bus().

When looking down child bus, it should look parent bridge's
bus number, not child bus's.

Cc: Blue Swirl <blauwirbel@gmail.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
---
 hw/pci.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/hw/pci.c b/hw/pci.c
index 0dbca17..b6e6bbe 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -1556,10 +1556,10 @@ PCIBus *pci_find_bus(PCIBus *bus, int bus_num)
     }
 
     /* try child bus */
-    QLIST_FOREACH(sec, &bus->child, sibling) {
-        if (!bus->parent_dev /* pci host bridge */
-            || (pci_bus_num(sec) <= bus_num &&
-                bus_num <= bus->parent_dev->config[PCI_SUBORDINATE_BUS]) ) {
+    if (!bus->parent_dev /* pci host bridge */
+        || (pci_bus_num(bus) <= bus_num &&
+            bus_num <= bus->parent_dev->config[PCI_SUBORDINATE_BUS])) {
+        QLIST_FOREACH(sec, &bus->child, sibling) {
             ret = pci_find_bus(sec, bus_num);
             if (ret) {
                 return ret;
-- 
1.6.6.1


-- 
yamahata

[Qemu-devel] Re: [PATCH] pci: fix pci_find_bus().

[Michael S. Tsirkin]

On Fri, Apr 09, 2010 at 07:13:24PM +0900, Isaku Yamahata wrote:
> When looking down child bus, it looked parent bridge's
> bus number.
> It should look child bridge's.
> 
> Cc: Blue Swirl <blauwirbel@gmail.com>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
> ---
>  hw/pci.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/pci.c b/hw/pci.c
> index 0dbca17..2f6907b 100644
> --- a/hw/pci.c
> +++ b/hw/pci.c
> @@ -1557,9 +1557,9 @@ PCIBus *pci_find_bus(PCIBus *bus, int bus_num)
>  
>      /* try child bus */
>      QLIST_FOREACH(sec, &bus->child, sibling) {
> -        if (!bus->parent_dev /* pci host bridge */
> +        if (!sec->parent_dev /* pci host bridge */

I don't understand this first test. As far as I can tell
secondary bus must always have a device, as set by
pci_register_secondary_bus.  Should this
rather be assert(sec->parent_dev)?

>              || (pci_bus_num(sec) <= bus_num &&


And so the above should just use
sec->parent_dev->config[PCI_SECONDARY_BUS]
instead of a wrapper that tests sec->parent_dev.

> -                bus_num <= bus->parent_dev->config[PCI_SUBORDINATE_BUS]) ) {
> +                bus_num <= sec->parent_dev->config[PCI_SUBORDINATE_BUS]) ) {


>              ret = pci_find_bus(sec, bus_num);
>              if (ret) {

I think that in the above, we can just as well do
return pci_find_bus() - if multiple children claim
the same bus range, on real hardware only one
of them will claim the transaction.

>                  return ret;

I find the use of recursion here confusing.
Since as pointed out above this can be a tail recursion,
it can easily be converted to a loop.
How does the below look, for example?
Note: completely untested, likely broken:

diff --git a/hw/pci.c b/hw/pci.c
index b6abd67..e9d6def 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -1546,26 +1546,33 @@ static void pci_bridge_write_config(PCIDevice *d,
 
 PCIBus *pci_find_bus(PCIBus *bus, int bus_num)
 {
-    PCIBus *sec, *ret;
+    PCIBus *sec;
+    bool found;
 
-    if (!bus)
+    if (!bus) {
         return NULL;
+    }
 
     if (pci_bus_num(bus) == bus_num) {
         return bus;
     }
 
     /* try child bus */
-    QLIST_FOREACH(sec, &bus->child, sibling) {
-        if (!bus->parent_dev /* pci host bridge */
-            || (pci_bus_num(sec) <= bus_num &&
-                bus_num <= bus->parent_dev->config[PCI_SUBORDINATE_BUS]) ) {
-            ret = pci_find_bus(sec, bus_num);
-            if (ret) {
-                return ret;
+    do {
+	 found = false;
+        QLIST_FOREACH(sec, &bus->child, sibling) {
+            assert(sec->parent_dev);
+            if (sec->parent_dev->config[PCI_SECONDARY_BUS] == bus_num) {
+                return sec;
+            }
+            if (sec->parent_dev->config[PCI_SECONDARY_BUS] < bus_num &&
+                bus_num <= sec->parent_dev->config[PCI_SUBORDINATE_BUS]) {
+                bus = sec;
+                found = true;
+                break;
             }
         }
-    }
+    } while (found);
 
     return NULL;
 }

> -- 
> 1.6.6.1
> 

[Qemu-devel] Re: [PATCH] pci: fix pci_find_bus().

[Michael S. Tsirkin]

On Sat, Apr 10, 2010 at 08:48:35AM +0900, Isaku Yamahata wrote:
> Oh I sent out the wrong one. This is the correct one.
> Sorry for noise.
> 
> >From 370c23c837070f78ca5715f032eacbf6747d42fb Mon Sep 17 00:00:00 2001
> Message-Id: <370c23c837070f78ca5715f032eacbf6747d42fb.1270856742.git.yamahata@valinux.co.jp>
> In-Reply-To: <cover.1270856742.git.yamahata@valinux.co.jp>
> References: <cover.1270856742.git.yamahata@valinux.co.jp>
> From: Isaku Yamahata <yamahata@valinux.co.jp>
> Date: Fri, 9 Apr 2010 19:09:35 +0900
> Subject: [PATCH] pci: fix pci_find_bus().
> 
> When looking down child bus, it should look parent bridge's
> bus number, not child bus's.
> 
> Cc: Blue Swirl <blauwirbel@gmail.com>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
> ---
>  hw/pci.c |    8 ++++----
>  1 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/pci.c b/hw/pci.c
> index 0dbca17..b6e6bbe 100644
> --- a/hw/pci.c
> +++ b/hw/pci.c
> @@ -1556,10 +1556,10 @@ PCIBus *pci_find_bus(PCIBus *bus, int bus_num)
>      }
>  
>      /* try child bus */
> -    QLIST_FOREACH(sec, &bus->child, sibling) {
> -        if (!bus->parent_dev /* pci host bridge */
> -            || (pci_bus_num(sec) <= bus_num &&
> -                bus_num <= bus->parent_dev->config[PCI_SUBORDINATE_BUS]) ) {
> +    if (!bus->parent_dev /* pci host bridge */
> +        || (pci_bus_num(bus) <= bus_num &&

Better use PCI_SECONDARY_BUS here directly, we know parent_dev is
non-NULL.

> +            bus_num <= bus->parent_dev->config[PCI_SUBORDINATE_BUS])) {
> +        QLIST_FOREACH(sec, &bus->child, sibling) {
>              ret = pci_find_bus(sec, bus_num);
>              if (ret) {
>                  return ret;

What do you think about converting code to loop
as I suggested earlier?

> -- 
> 1.6.6.1
> 
> 
> -- 
> yamahata

[Qemu-devel] [PATCH v2] pci: fix pci_find_bus().

[Isaku Yamahata]

When looking down child bus, it should look parent bridge's
bus number, not child bus's.
Optimized tail recursion and style fix.

Cc: Blue Swirl <blauwirbel@gmail.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
---
 hw/pci.c |   25 ++++++++++++++++---------
 1 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/hw/pci.c b/hw/pci.c
index 2355232..6c0cc7b 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -1546,23 +1546,30 @@ static void pci_bridge_write_config(PCIDevice *d,
 
 PCIBus *pci_find_bus(PCIBus *bus, int bus_num)
 {
-    PCIBus *sec, *ret;
+    PCIBus *sec;
 
-    if (!bus)
+    if (!bus) {
         return NULL;
+    }
 
     if (pci_bus_num(bus) == bus_num) {
         return bus;
     }
 
     /* try child bus */
-    QLIST_FOREACH(sec, &bus->child, sibling) {
-        if (!bus->parent_dev /* pci host bridge */
-            || (pci_bus_num(sec) <= bus_num &&
-                bus_num <= bus->parent_dev->config[PCI_SUBORDINATE_BUS]) ) {
-            ret = pci_find_bus(sec, bus_num);
-            if (ret) {
-                return ret;
+    if (!bus->parent_dev /* host pci bridge */ ||
+        (bus->parent_dev->config[PCI_SECONDARY_BUS] < bus_num &&
+         bus_num <= bus->parent_dev->config[PCI_SUBORDINATE_BUS])) {
+        for (; bus; bus = sec) {
+            QLIST_FOREACH(sec, &bus->child, sibling) {
+                assert(sec->parent_dev);
+                if (sec->parent_dev->config[PCI_SECONDARY_BUS] == bus_num) {
+                    return sec;
+                }
+                if (sec->parent_dev->config[PCI_SECONDARY_BUS] < bus_num &&
+                    bus_num <= sec->parent_dev->config[PCI_SUBORDINATE_BUS]) {
+                    break;
+                }
             }
         }
     }
-- 
1.6.6.1

[Qemu-devel] Re: [PATCH v2] pci: fix pci_find_bus().

[Blue Swirl]

Thanks, applied.

On 4/12/10, Isaku Yamahata <yamahata@valinux.co.jp> wrote:
> When looking down child bus, it should look parent bridge's
>  bus number, not child bus's.
>
> Optimized tail recursion and style fix.
>
>
>  Cc: Blue Swirl <blauwirbel@gmail.com>
>  Cc: "Michael S. Tsirkin" <mst@redhat.com>
>  Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
>  ---
>
>  hw/pci.c |   25 ++++++++++++++++---------
>   1 files changed, 16 insertions(+), 9 deletions(-)
>
>
>  diff --git a/hw/pci.c b/hw/pci.c
>
> index 2355232..6c0cc7b 100644
>
> --- a/hw/pci.c
>  +++ b/hw/pci.c
>
> @@ -1546,23 +1546,30 @@ static void pci_bridge_write_config(PCIDevice *d,
>
>
>   PCIBus *pci_find_bus(PCIBus *bus, int bus_num)
>
>  {
>  -    PCIBus *sec, *ret;
>  +    PCIBus *sec;
>
>
> -    if (!bus)
>  +    if (!bus) {
>          return NULL;
>  +    }
>
>
>      if (pci_bus_num(bus) == bus_num) {
>          return bus;
>
>      }
>
>      /* try child bus */
>  -    QLIST_FOREACH(sec, &bus->child, sibling) {
>  -        if (!bus->parent_dev /* pci host bridge */
>  -            || (pci_bus_num(sec) <= bus_num &&
>  -                bus_num <= bus->parent_dev->config[PCI_SUBORDINATE_BUS]) ) {
>
> -            ret = pci_find_bus(sec, bus_num);
>  -            if (ret) {
>  -                return ret;
>  +    if (!bus->parent_dev /* host pci bridge */ ||
>  +        (bus->parent_dev->config[PCI_SECONDARY_BUS] < bus_num &&
>
> +         bus_num <= bus->parent_dev->config[PCI_SUBORDINATE_BUS])) {
>
> +        for (; bus; bus = sec) {
>
> +            QLIST_FOREACH(sec, &bus->child, sibling) {
>
> +                assert(sec->parent_dev);
>  +                if (sec->parent_dev->config[PCI_SECONDARY_BUS] == bus_num) {
>  +                    return sec;
>  +                }
>  +                if (sec->parent_dev->config[PCI_SECONDARY_BUS] < bus_num &&
>
> +                    bus_num <= sec->parent_dev->config[PCI_SUBORDINATE_BUS]) {
>  +                    break;
>  +                }
>              }
>          }
>      }
>
> --
>  1.6.6.1
>
>
>

[Qemu-devel] [PATCH] pci: fix pci_find_bus()

[Isaku Yamahata]

typo in c021f8e65f5009a5ab5711d9d5326fcab553ef1c.
comparison fix.

Cc: Blue Swirl <blauwirbel@gmail.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
---
 hw/pci.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/hw/pci.c b/hw/pci.c
index 9ad63dd..e91d2e6 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -1558,7 +1558,7 @@ PCIBus *pci_find_bus(PCIBus *bus, int bus_num)
     /* try child bus */
     QLIST_FOREACH(sec, &bus->child, sibling) {
         if (!bus->parent_dev /* pci host bridge */
-            || (pci_bus_num(sec) >= bus_num &&
+            || (pci_bus_num(sec) <= bus_num &&
                 bus_num <= bus->parent_dev->config[PCI_SUBORDINATE_BUS]) ) {
             ret = pci_find_bus(sec, bus_num);
             if (ret) {
-- 
1.6.6.1