Re: [Xen-devel] [PATCH] Initialize ioreq_t in hvmemul_do_io()

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 22 May 2014 14:14
> To: Andrew Cooper; Paul Durrant
> Cc: xen-devel@xxxxxxxxxxxxx; Keir (Xen.org)
> Subject: Re: [PATCH] Initialize ioreq_t in hvmemul_do_io()
> 
> >>> On 22.05.14 at 14:48, <paul.durrant@xxxxxxxxxx> wrote:
> > All relevant fields of the ioreq_t are properly initialized but coverity
> > complains about vp_eport being uninitialized (ID 1215178) because it is
> > the subject of a struct copy in hvm_send_assist_req().
> >
> > Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> > Cc: Keir Fraser <keir@xxxxxxx>
> > Cc: Jan Beulich <jbeulich@xxxxxxxx>
> > Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > ---
> >  xen/arch/x86/hvm/emulate.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
> > index 904c71a..e516194 100644
> > --- a/xen/arch/x86/hvm/emulate.c
> > +++ b/xen/arch/x86/hvm/emulate.c
> > @@ -57,7 +57,7 @@ static int hvmemul_do_io(
> >      int value_is_ptr = (p_data == NULL);
> >      struct vcpu *curr = current;
> >      struct hvm_vcpu_io *vio;
> > -    ioreq_t p;
> > +    ioreq_t p = { 0 };
> 
> To be honest, I dislike fixes like this to address tool shortcomings. It's
> not like this is giaramteed to be just a single instruction that gets
> added (maybe the compiler can figure this, but I would want to rely
> on it.
> 

I could always change hvm_send_assist_req() to only copy the relevant fields 
from the proto structure, as it used to in earlier versions of my patch.

  Paul

> If it's known to just be one member, can't that (with a suitable but
> brief comment) be added to the set of field initializations further
> down in the function? That would still be code there just to please
> Coverity, but it would be guaranteed to be a single instruction.
> 
> Btw., Andrew, can one identify at build time that a build is done
> just for Coverity's inspection? If so, rather than a comment a
> suitable preprocessor conditional might be enough documentation
> in cases like this.
> 
> Jan


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