[PATCH] sysctl: adjust XEN_SYSCTL_cputopoinfo behavior

[PATCH] sysctl: adjust XEN_SYSCTL_cputopoinfo behavior

[Jan Beulich]

[-- Attachment #1: Type: text/plain, Size: 2169 bytes --]

The new function's implementation, other than the original one of
XEN_SYSCTL_topologyinfo, didn't allow the caller to get what it needs
(if e.g. it's after the data for just one specific CPU) with just one
hypercall, without caring about the total number of CPUs in the system.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/common/sysctl.c
+++ b/xen/common/sysctl.c
@@ -358,15 +358,9 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xe
         {
             xen_sysctl_cputopo_t cputopo = { 0 };
 
-            if ( ti->num_cpus < num_cpus )
-            {
-                ret = -ENOBUFS;
-                i = num_cpus;
-            }
-            else
-                i = 0;
-
-            for ( ; i < num_cpus; i++ )
+            if ( num_cpus > ti->num_cpus )
+                num_cpus = ti->num_cpus;
+            for ( i = 0; i < num_cpus; ++i )
             {
                 if ( cpu_present(i) )
                 {
@@ -393,7 +387,7 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xe
         else
             i = num_cpus;
 
-        if ( (!ret || (ret == -ENOBUFS)) && (ti->num_cpus != i) )
+        if ( !ret && (ti->num_cpus != i) )
         {
             ti->num_cpus = i;
             if ( __copy_field_to_guest(u_sysctl, op,
--- a/xen/include/public/sysctl.h
+++ b/xen/include/public/sysctl.h
@@ -482,10 +482,11 @@ DEFINE_XEN_GUEST_HANDLE(xen_sysctl_cputo
  *  - otherwise it's the number of entries in 'cputopo'
  *
  * OUT:
- *  - If 'num_cpus' is less than the number Xen needs to write, -ENOBUFS shall
- *    be returned and 'num_cpus' updated to reflect the intended number.
- *  - On success, 'num_cpus' shall indicate the number of entries written, which
- *    may be less than the maximum.
+ *  - If 'num_cpus' is less than the number Xen wants to write but the handle
+ *    handle is not a NULL one, partial data gets returned and 'num_cpus' gets
+ *    updated to reflect the intended number.
+ *  - Otherwise, 'num_cpus' shall indicate the number of entries written, which
+ *    may be less than the input value.
  */
 struct xen_sysctl_cputopoinfo {
     uint32_t num_cpus;




[-- Attachment #2: sysctl-cputopoinfo-partial.patch --]
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sysctl: adjust XEN_SYSCTL_cputopoinfo behavior

The new function's implementation, other than the original one of
XEN_SYSCTL_topologyinfo, didn't allow the caller to get what it needs
(if e.g. it's after the data for just one specific CPU) with just one
hypercall, without caring about the total number of CPUs in the system.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/common/sysctl.c
+++ b/xen/common/sysctl.c
@@ -358,15 +358,9 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xe
         {
             xen_sysctl_cputopo_t cputopo = { 0 };
 
-            if ( ti->num_cpus < num_cpus )
-            {
-                ret = -ENOBUFS;
-                i = num_cpus;
-            }
-            else
-                i = 0;
-
-            for ( ; i < num_cpus; i++ )
+            if ( num_cpus > ti->num_cpus )
+                num_cpus = ti->num_cpus;
+            for ( i = 0; i < num_cpus; ++i )
             {
                 if ( cpu_present(i) )
                 {
@@ -393,7 +387,7 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xe
         else
             i = num_cpus;
 
-        if ( (!ret || (ret == -ENOBUFS)) && (ti->num_cpus != i) )
+        if ( !ret && (ti->num_cpus != i) )
         {
             ti->num_cpus = i;
             if ( __copy_field_to_guest(u_sysctl, op,
--- a/xen/include/public/sysctl.h
+++ b/xen/include/public/sysctl.h
@@ -482,10 +482,11 @@ DEFINE_XEN_GUEST_HANDLE(xen_sysctl_cputo
  *  - otherwise it's the number of entries in 'cputopo'
  *
  * OUT:
- *  - If 'num_cpus' is less than the number Xen needs to write, -ENOBUFS shall
- *    be returned and 'num_cpus' updated to reflect the intended number.
- *  - On success, 'num_cpus' shall indicate the number of entries written, which
- *    may be less than the maximum.
+ *  - If 'num_cpus' is less than the number Xen wants to write but the handle
+ *    handle is not a NULL one, partial data gets returned and 'num_cpus' gets
+ *    updated to reflect the intended number.
+ *  - Otherwise, 'num_cpus' shall indicate the number of entries written, which
+ *    may be less than the input value.
  */
 struct xen_sysctl_cputopoinfo {
     uint32_t num_cpus;

[-- Attachment #3: Type: text/plain, Size: 126 bytes --]

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Re: [PATCH] sysctl: adjust XEN_SYSCTL_cputopoinfo behavior

[Boris Ostrovsky]

On 07/13/2015 11:53 AM, Jan Beulich wrote:
> The new function's implementation, other than the original one of
> XEN_SYSCTL_topologyinfo, didn't allow the caller to get what it needs
> (if e.g. it's after the data for just one specific CPU) with just one
> hypercall, without caring about the total number of CPUs in the system.

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

Would we want a similar update for XEN_SYSCTL_numainfo?


-boris


>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>
> --- a/xen/common/sysctl.c
> +++ b/xen/common/sysctl.c
> @@ -358,15 +358,9 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xe
>           {
>               xen_sysctl_cputopo_t cputopo = { 0 };
>   
> -            if ( ti->num_cpus < num_cpus )
> -            {
> -                ret = -ENOBUFS;
> -                i = num_cpus;
> -            }
> -            else
> -                i = 0;
> -
> -            for ( ; i < num_cpus; i++ )
> +            if ( num_cpus > ti->num_cpus )
> +                num_cpus = ti->num_cpus;
> +            for ( i = 0; i < num_cpus; ++i )
>               {
>                   if ( cpu_present(i) )
>                   {
> @@ -393,7 +387,7 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xe
>           else
>               i = num_cpus;
>   
> -        if ( (!ret || (ret == -ENOBUFS)) && (ti->num_cpus != i) )
> +        if ( !ret && (ti->num_cpus != i) )
>           {
>               ti->num_cpus = i;
>               if ( __copy_field_to_guest(u_sysctl, op,
> --- a/xen/include/public/sysctl.h
> +++ b/xen/include/public/sysctl.h
> @@ -482,10 +482,11 @@ DEFINE_XEN_GUEST_HANDLE(xen_sysctl_cputo
>    *  - otherwise it's the number of entries in 'cputopo'
>    *
>    * OUT:
> - *  - If 'num_cpus' is less than the number Xen needs to write, -ENOBUFS shall
> - *    be returned and 'num_cpus' updated to reflect the intended number.
> - *  - On success, 'num_cpus' shall indicate the number of entries written, which
> - *    may be less than the maximum.
> + *  - If 'num_cpus' is less than the number Xen wants to write but the handle
> + *    handle is not a NULL one, partial data gets returned and 'num_cpus' gets
> + *    updated to reflect the intended number.
> + *  - Otherwise, 'num_cpus' shall indicate the number of entries written, which
> + *    may be less than the input value.
>    */
>   struct xen_sysctl_cputopoinfo {
>       uint32_t num_cpus;
>
>
>
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel

Re: [PATCH] sysctl: adjust XEN_SYSCTL_cputopoinfo behavior

[Jan Beulich]

>>> On 13.07.15 at 19:43, <boris.ostrovsky@oracle.com> wrote:
> On 07/13/2015 11:53 AM, Jan Beulich wrote:
>> The new function's implementation, other than the original one of
>> XEN_SYSCTL_topologyinfo, didn't allow the caller to get what it needs
>> (if e.g. it's after the data for just one specific CPU) with just one
>> hypercall, without caring about the total number of CPUs in the system.
> 
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> 
> Would we want a similar update for XEN_SYSCTL_numainfo?

I thought there was a second such case, but seeing
XEN_SYSCTL_pcitopoinfo not be it I didn't look further assuming
I mis-remembered. So yes, imo that one should be adjusted in the
same way.

Jan

Re: [PATCH] sysctl: adjust XEN_SYSCTL_cputopoinfo behavior

[Ian Campbell]

On Mon, 2015-07-13 at 16:53 +0100, Jan Beulich wrote:
> The new function's implementation, other than the original one of

FWIW "other than the" would normally be expressed as "unlike the".

> XEN_SYSCTL_topologyinfo, didn't allow the caller to get what it needs
> (if e.g. it's after the data for just one specific CPU) with just one
> hypercall, without caring about the total number of CPUs in the system.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Acked-by: Ian Campbell <ian.campbell@citrix.com>
> 
> --- a/xen/common/sysctl.c
> +++ b/xen/common/sysctl.c
> @@ -358,15 +358,9 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xe
>          {
>              xen_sysctl_cputopo_t cputopo = { 0 };
>  
> -            if ( ti->num_cpus < num_cpus )
> -            {
> -                ret = -ENOBUFS;
> -                i = num_cpus;
> -            }
> -            else
> -                i = 0;
> -
> -            for ( ; i < num_cpus; i++ )
> +            if ( num_cpus > ti->num_cpus )
> +                num_cpus = ti->num_cpus;
> +            for ( i = 0; i < num_cpus; ++i )
>              {
>                  if ( cpu_present(i) )
>                  {
> @@ -393,7 +387,7 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xe
>          else
>              i = num_cpus;
>  
> -        if ( (!ret || (ret == -ENOBUFS)) && (ti->num_cpus != i) )
> +        if ( !ret && (ti->num_cpus != i) )
>          {
>              ti->num_cpus = i;
>              if ( __copy_field_to_guest(u_sysctl, op,
> --- a/xen/include/public/sysctl.h
> +++ b/xen/include/public/sysctl.h
> @@ -482,10 +482,11 @@ DEFINE_XEN_GUEST_HANDLE(xen_sysctl_cputo
>   *  - otherwise it's the number of entries in 'cputopo'
>   *
>   * OUT:
> - *  - If 'num_cpus' is less than the number Xen needs to write, -ENOBUFS shall
> - *    be returned and 'num_cpus' updated to reflect the intended number.
> - *  - On success, 'num_cpus' shall indicate the number of entries written, which
> - *    may be less than the maximum.
> + *  - If 'num_cpus' is less than the number Xen wants to write but the handle
> + *    handle is not a NULL one, partial data gets returned and 'num_cpus' gets
> + *    updated to reflect the intended number.
> + *  - Otherwise, 'num_cpus' shall indicate the number of entries written, which
> + *    may be less  than the input value.
>   */
>  struct xen_sysctl_cputopoinfo {
>      uint32_t num_cpus;
> 
> 
>