Re: [PATCH v2 2/6] accel: accel_available() function

[Eduardo Habkost]

On Thu, Nov 26, 2020 at 10:14:31AM +0100, Claudio Fontana wrote:
> Hi Eduardo,
> 
> On 11/25/20 9:56 PM, Eduardo Habkost wrote:
> > This function will be used to replace the xen_available() and
> > kvm_available() functions from arch_init.c.
> > 
> > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> > ---
> > Cc: Richard Henderson <richard.henderson@linaro.org>
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: Claudio Fontana <cfontana@suse.de>
> > Cc: Roman Bolshakov <r.bolshakov@yadro.com>
> > ---
> >  include/sysemu/accel.h | 1 +
> >  accel/accel.c          | 5 +++++
> >  2 files changed, 6 insertions(+)
> > 
> > diff --git a/include/sysemu/accel.h b/include/sysemu/accel.h
> > index e08b8ab8fa..a4a00c75c8 100644
> > --- a/include/sysemu/accel.h
> > +++ b/include/sysemu/accel.h
> > @@ -67,6 +67,7 @@ typedef struct AccelClass {
> >      OBJECT_GET_CLASS(AccelClass, (obj), TYPE_ACCEL)
> >  
> >  AccelClass *accel_find(const char *opt_name);
> > +bool accel_available(const char *name);
> >  int accel_init_machine(AccelState *accel, MachineState *ms);
> >  
> >  /* Called just before os_setup_post (ie just before drop OS privs) */
> > diff --git a/accel/accel.c b/accel/accel.c
> > index cb555e3b06..4a64a2b38a 100644
> > --- a/accel/accel.c
> > +++ b/accel/accel.c
> > @@ -46,6 +46,11 @@ AccelClass *accel_find(const char *opt_name)
> >      return ac;
> >  }
> >  
> > +bool accel_available(const char *name)
> > +{
> > +    return accel_find(name) != NULL;
> 
> 
> accel_find() in its implementation allocates and then frees memory to 
> generate the string,
> the user of accel_available() might be unaware and overuse leading to 
> fragmentation/performance issues?

Is that a real issue?  We had only 3 users of kvm_available() and
xen_available() since those functions were added 10 years ago.

Do you have any suggestions on what we should do?

-- 
Eduardo