Xen devel - Feb 2011 - [PATCH] qemu-xen: read default pci passthrough values

If there are no devices assigned to the domain at boot, we don''t read
the default pci passthrough parameters.
This patch fixes it.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

diff --git a/xenstore.c b/xenstore.c
index d364a5e..3fd69aa 100644
--- a/xenstore.c
+++ b/xenstore.c
@@ -738,9 +738,8 @@ void xenstore_parse_domain_config(int hvm_domid)
 
     free(params);
     params = xs_read(xsh, XBT_NULL, buf, &len);
-    if (params == NULL)
-        goto out;
-    num = atoi(params);
+    if (params != NULL)
+        num = atoi(params);
 
     /* get the pci pass-through parameter */
     if (pasprintf(&buf,
"/local/domain/0/backend/pci/%u/%u/msitranslate",

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Stefano Stabellini writes ("[Xen-devel] [PATCH] qemu-xen: read default pci
passthrough values"):
> If there are no devices assigned to the domain at boot, we don''t
read
> the default pci passthrough parameters.
> This patch fixes it.
The semantics you intend seem sensible, but:

The variable "num" seems completely unused after we went to all the
effort of reading num_devs to get it.  The code seems to read
.../num_devs just to check that the key exists, and doesn''t mind
"0"
as an answer.  With your patch applied, we don''t even care whether the
key exists.

So why do we bother reading .../num_devs and converting it to an
integer and assigning it to nums ?

Ian.

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On Thu, 3 Feb 2011, Ian Jackson wrote:
> Stefano Stabellini writes ("[Xen-devel] [PATCH] qemu-xen: read default
pci passthrough values"):
> > If there are no devices assigned to the domain at boot, we
don''t read
> > the default pci passthrough parameters.
> > This patch fixes it.
> 
> The semantics you intend seem sensible, but:
> 
> The variable "num" seems completely unused after we went to all
the
> effort of reading num_devs to get it.  The code seems to read
> .../num_devs just to check that the key exists, and doesn''t mind
"0"
> as an answer.  With your patch applied, we don''t even care whether
the
> key exists.
> 
> So why do we bother reading .../num_devs and converting it to an
> integer and assigning it to nums ?
That is a very good point. Reading num_devs is completely useless hence
I am removing it.

---


diff --git a/xenstore.c b/xenstore.c
index d364a5e..eed4955 100644
--- a/xenstore.c
+++ b/xenstore.c
@@ -731,18 +731,7 @@ void xenstore_parse_domain_config(int hvm_domid)
      * hvm_domid is always equal to domid */
     hvm_domid = domid;
 
-    /* get the pci pass-through parameter */
-    if (pasprintf(&buf,
"/local/domain/0/backend/pci/%u/%u/num_devs",
-                  hvm_domid, pci_devid) == -1)
-        goto out;
-
-    free(params);
-    params = xs_read(xsh, XBT_NULL, buf, &len);
-    if (params == NULL)
-        goto out;
-    num = atoi(params);
-
-    /* get the pci pass-through parameter */
+    /* get the pci pass-through parameters */
     if (pasprintf(&buf,
"/local/domain/0/backend/pci/%u/%u/msitranslate",
                   hvm_domid, pci_devid) != -1)
     {

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Stefano Stabellini writes ("Re: [Xen-devel] [PATCH] qemu-xen: read default
pci passthrough values"):
> That is a very good point. Reading num_devs is completely useless hence
> I am removing it.
Great, applied, thanks.

Ian.

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