Re: [PATCH v4 4/5] common/domain: add a domain context record for shared_info...

[Julien Grall <julien@xxxxxxx>]

Hi,

On 21/05/2020 17:00, Paul Durrant wrote:
> > -----Original Message-----
> > From: Paul Durrant <xadimgnik@xxxxxxxxx>
> > Sent: 21 May 2020 16:26
> > To: 'Julien Grall' <julien@xxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
> > Cc: 'Paul Durrant' <pdurrant@xxxxxxxxxx>; 'Ian Jackson' 
> > <ian.jackson@xxxxxxxxxxxxx>; 'Wei Liu'
> > <wl@xxxxxxx>; 'Andrew Cooper' <andrew.cooper3@xxxxxxxxxx>; 'George Dunlap' 
> > <george.dunlap@xxxxxxxxxx>;
> > 'Jan Beulich' <jbeulich@xxxxxxxx>; 'Stefano Stabellini' <sstabellini@xxxxxxxxxx>
> > Subject: RE: [PATCH v4 4/5] common/domain: add a domain context record for 
> > shared_info...
> >
> > > -----Original Message-----
> > [snip]
> > > > diff --git a/xen/common/domain.c b/xen/common/domain.c
> > > > index 7cc9526139..14e96c3bc2 100644
> > > > --- a/xen/common/domain.c
> > > > +++ b/xen/common/domain.c
> > > > @@ -33,6 +33,7 @@
> > > >    #include <xen/xenoprof.h>
> > > >    #include <xen/irq.h>
> > > >    #include <xen/argo.h>
> > > > +#include <xen/save.h>
> > > >    #include <asm/debugger.h>
> > > >    #include <asm/p2m.h>
> > > >    #include <asm/processor.h>
> > > > @@ -1649,6 +1650,64 @@ int continue_hypercall_on_cpu(
> > > >        return 0;
> > > >    }
> > > >
> > > > +static int save_shared_info(const struct domain *d, struct domain_context *c,
> > > > +                            bool dry_run)
> > > > +{
> > > > +    struct domain_shared_info_context ctxt = {
> > > > +#ifdef CONFIG_COMPAT
> > > > +        .flags = has_32bit_shinfo(d) ? DOMAIN_SAVE_32BIT_SHINFO : 0,
> > > > +#endif
> > > > +        .buffer_size = sizeof(shared_info_t),
> > > > +    };
> > > > +    size_t hdr_size = offsetof(typeof(ctxt), buffer);
> > > > +    int rc;
> > > > +
> > > > +    rc = DOMAIN_SAVE_BEGIN(SHARED_INFO, c, 0);
> > > > +    if ( rc )
> > > > +        return rc;
> > > > +
> > > > +    rc = domain_save_data(c, &ctxt, hdr_size);
> > > > +    if ( rc )
> > > > +        return rc;
> > > > +
> > > > +    rc = domain_save_data(c, d->shared_info, ctxt.buffer_size);
> > > > +    if ( rc )
> > > > +        return rc;
> > > > +
> > > > +    return domain_save_end(c);
> > > > +}
> > > > +
> > > > +static int load_shared_info(struct domain *d, struct domain_context *c)
> > > > +{
> > > > +    struct domain_shared_info_context ctxt;
> > > > +    size_t hdr_size = offsetof(typeof(ctxt), buffer);
> > > > +    unsigned int i;
> > > > +    int rc;
> > > > +
> > > > +    rc = DOMAIN_LOAD_BEGIN(SHARED_INFO, c, &i);
> > > > +    if ( rc || i ) /* expect only a single instance */
> > > > +        return rc;
> > > This will return 0 if there is multiple instance. Is it intended?
> > No, it ought to be an error... probably ENOENT.
> Actually I think ENXIO might be better... ENOENT tends to imply something is 
> missing rather than unexpected.
ENXIO could work. Another one would be E2BIG.

I don't have a preference.

Cheers,

--
Julien Grall