qemu discuss - Apr 2007 - [PATCH] kqemu becomes unusable, all available instances in use

The Solaris kqemu kernel module does not release a device instance
when the /dev/kqemu file is closed.  Starting with the 17th open
attempt on /dev/kqemu, kqemu becomes unusable, we get ENXIO errors,
and the following message is logged to the console and /var/adm/messages:

   NOTICE: all available instances in use



Since kqemu_open() detects a free kqemu instance by searching the
kqemu_ssp soft state structure for an unallocated soft state instance,
there should be some code that clears the soft state instance when a
kqemu device instance is no longer in use.


I''m using the fix included below, it frees the soft state from the
kqemu_close() entry point.  It also removes an extra call to
ddi_soft_state_free() in the driver''s attach entry point, which is
trying to free something in the error case when nothing has been
allocated.


diff -ru8 /tmp/kqemu-1.3.0pre11-ben/kqemu-solaris.c
kqemu-1.3.0pre11-ben/kqemu-solaris.c
--- /tmp/kqemu-1.3.0pre11-ben/kqemu-solaris.c	2007-03-20 20:10:10.000000000
+0100
+++ kqemu-1.3.0pre11-ben/kqemu-solaris.c	2007-03-31 00:52:06.174919073 +0200
@@ -477,16 +477,17 @@
         kqemu_log_d("close");
 
         if (ks == NULL)
                 return (ENXIO);
         if (ks->state) {
                 kqemu_delete(ks->state);
                 ks->state = NULL;
         }
+	ddi_soft_state_free(kqemu_ssp, instance);
         return (0);
 }
 
 /*
  * Unlike on Linux, a 64-bit SunOS kernel does not imply 64-bit
  * userland. QEMU will need to be ported to 64-bit for the 64-bit
  * accelerator to work. 32-bit qemu in accelerated mode on 64-bit
  * kernel will likely never be supported.
@@ -614,17 +615,16 @@
         switch(cmd) {
                 char s[16];
         case DDI_ATTACH:
                 snprintf(s, sizeof (s), "%d", instance);
                 if (ddi_create_minor_node(dip, s, S_IFCHR,
                     instance, DDI_PSEUDO, 0) != DDI_SUCCESS) {
                         cmn_err(CE_NOTE, "attach(%d): could not add "
                             "character node", instance);
-                        ddi_soft_state_free(kqemu_ssp, instance);
                         return (DDI_FAILURE);
                 }
                 kqemu_dip = dip;
                 atomic_add_32(&kqemu_busy, 1);
                 return (DDI_SUCCESS);
         default:
                 return (DDI_SUCCESS);
         }

> The Solaris kqemu kernel module does not release a
> device instance
> when the /dev/kqemu file is closed.  Starting with
> the 17th open
> attempt on /dev/kqemu, kqemu becomes unusable, we get
> ENXIO errors,
> and the following message is logged to the console
> and /var/adm/messages:
> 
>    NOTICE: all available instances in use
> Since kqemu_open() detects a free kqemu instance by
> searching the
> kqemu_ssp soft state structure for an unallocated
> soft state instance,
> there should be some code that clears the soft state
> instance when a
> kqemu device instance is no longer in use.
Nice work.  definitely seems to fix that problem.  I plan on posting the updated
kqemu tarball in the next day or so.  I need to work out the details on
installing
both the 32-bit and 64-bit version at the same time.

Ben
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