Xen devel - Jan 2012 - [PATCH] tools/libxc: handle fallback in linux_privcmd_map_foreign_bulk properly

# HG changeset patch
# User Olaf Hering <olaf@aepfle.de>
# Date 1327584962 -3600
# Node ID aa0d678fece208975984e8e59ca223c07fc50c06
# Parent  89fdabcf315fdaabeebf05c51a6b3b6dd4c20e85
tools/libxc: handle fallback in linux_privcmd_map_foreign_bulk properly

If the first ioctl fails with ENOENT it means the command is known. If a
second attempt to map each gfn happens to fail then there is no need to
run the fallback code. Some gfns are paged and the fallback code would
not fix the failure. Instead return the EINVAL to the caller.

Signed-off-by: Olaf Hering <olaf@aepfle.de>

diff -r 89fdabcf315f -r aa0d678fece2 tools/libxc/xc_linux_osdep.c
--- a/tools/libxc/xc_linux_osdep.c
+++ b/tools/libxc/xc_linux_osdep.c
@@ -217,6 +217,7 @@ static void *linux_privcmd_map_foreign_b
 
     rc = ioctl(fd, IOCTL_PRIVCMD_MMAPBATCH_V2, &ioctlx);
 
+    /* Command was recognized, some gfn in arr are in paging state */
     if ( rc < 0 && errno == ENOENT )
     {
         for ( i = rc = 0; rc == 0 && i < num; i++ )
@@ -235,8 +236,8 @@ static void *linux_privcmd_map_foreign_b
             } while ( rc < 0 && errno == ENOENT && err[i] ==
-ENOENT );
         }
     }
-
-    if ( rc < 0 && errno == EINVAL && (int)num > 0 )
+    /* Command was not recognized, use fall back */
+    else if ( rc < 0 && errno == EINVAL && (int)num > 0 )
     {
         /*
          * IOCTL_PRIVCMD_MMAPBATCH_V2 is not supported - fall back to

> Date: Thu, 26 Jan 2012 14:36:30 +0100
> From: Olaf Hering <olaf@aepfle.de>
> To: xen-devel@lists.xensource.com
> Subject: [Xen-devel] [PATCH] tools/libxc: handle fallback in
> 	linux_privcmd_map_foreign_bulk properly
> Message-ID: <aa0d678fece208975984.1327584990@probook.site>
> Content-Type: text/plain; charset="us-ascii"
>
> # HG changeset patch
> # User Olaf Hering <olaf@aepfle.de>
> # Date 1327584962 -3600
> # Node ID aa0d678fece208975984e8e59ca223c07fc50c06
> # Parent  89fdabcf315fdaabeebf05c51a6b3b6dd4c20e85
> tools/libxc: handle fallback in linux_privcmd_map_foreign_bulk properly
>
> If the first ioctl fails with ENOENT it means the command is known. If a
> second attempt to map each gfn happens to fail then there is no need to
> run the fallback code. Some gfns are paged and the fallback code would
> not fix the failure. Instead return the EINVAL to the caller.
>
> Signed-off-by: Olaf Hering <olaf@aepfle.de>
Acked-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>

Thanks,
Andres
>
> diff -r 89fdabcf315f -r aa0d678fece2 tools/libxc/xc_linux_osdep.c
> --- a/tools/libxc/xc_linux_osdep.c
> +++ b/tools/libxc/xc_linux_osdep.c
> @@ -217,6 +217,7 @@ static void *linux_privcmd_map_foreign_b
>
>      rc = ioctl(fd, IOCTL_PRIVCMD_MMAPBATCH_V2, &ioctlx);
>
> +    /* Command was recognized, some gfn in arr are in paging state */
>      if ( rc < 0 && errno == ENOENT )
>      {
>          for ( i = rc = 0; rc == 0 && i < num; i++ )
> @@ -235,8 +236,8 @@ static void *linux_privcmd_map_foreign_b
>              } while ( rc < 0 && errno == ENOENT &&
err[i] == -ENOENT );
>          }
>      }
> -
> -    if ( rc < 0 && errno == EINVAL && (int)num > 0 )
> +    /* Command was not recognized, use fall back */
> +    else if ( rc < 0 && errno == EINVAL && (int)num
> 0 )
>      {
>          /*
>           * IOCTL_PRIVCMD_MMAPBATCH_V2 is not supported - fall back to
>
>

> > # HG changeset patch
> > # User Olaf Hering <olaf@aepfle.de>
> > # Date 1327584962 -3600
> > # Node ID aa0d678fece208975984e8e59ca223c07fc50c06
> > # Parent  89fdabcf315fdaabeebf05c51a6b3b6dd4c20e85
> > tools/libxc: handle fallback in linux_privcmd_map_foreign_bulk
properly
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>