Re: [Xen-devel] [PATCH v2 05/11] ioreq: add internal ioreq initialization support

["Roger Pau Monné" <roger.pau@citrix.com>]

On Tue, Sep 10, 2019 at 02:59:57PM +0200, Paul Durrant wrote:
> > -----Original Message-----
> > From: Roger Pau Monne <roger.pau@citrix.com>
> > Sent: 03 September 2019 17:14
> > To: xen-devel@lists.xenproject.org
> > Cc: Roger Pau Monne <roger.pau@citrix.com>; Jan Beulich <jbeulich@suse.com>; Andrew Cooper
> > <Andrew.Cooper3@citrix.com>; Wei Liu <wl@xen.org>; Paul Durrant <Paul.Durrant@citrix.com>
> > Subject: [PATCH v2 05/11] ioreq: add internal ioreq initialization support
> > @@ -736,33 +754,39 @@ static int hvm_ioreq_server_init(struct hvm_ioreq_server *s,
> >      int rc;
> > 
> >      s->target = d;
> > -
> > -    get_knownalive_domain(currd);
> > -    s->emulator = currd;
> > -
> >      spin_lock_init(&s->lock);
> > -    INIT_LIST_HEAD(&s->ioreq_vcpu_list);
> > -    spin_lock_init(&s->bufioreq_lock);
> > -
> > -    s->ioreq.gfn = INVALID_GFN;
> > -    s->bufioreq.gfn = INVALID_GFN;
> > 
> >      rc = hvm_ioreq_server_alloc_rangesets(s, id);
> >      if ( rc )
> >          return rc;
> > 
> > -    s->bufioreq_handling = bufioreq_handling;
> > -
> > -    for_each_vcpu ( d, v )
> > +    if ( !hvm_ioreq_is_internal(id) )
> >      {
> > -        rc = hvm_ioreq_server_add_vcpu(s, v);
> > -        if ( rc )
> > -            goto fail_add;
> > +        get_knownalive_domain(currd);
> > +
> > +        s->emulator = currd;
> > +        INIT_LIST_HEAD(&s->ioreq_vcpu_list);
> > +        spin_lock_init(&s->bufioreq_lock);
> > +
> > +        s->ioreq.gfn = INVALID_GFN;
> > +        s->bufioreq.gfn = INVALID_GFN;
> > +
> > +        s->bufioreq_handling = bufioreq_handling;
> > +
> > +        for_each_vcpu ( d, v )
> > +        {
> > +            rc = hvm_ioreq_server_add_vcpu(s, v);
> > +            if ( rc )
> > +                goto fail_add;
> > +        }
> >      }
> > +    else
> > +        s->handler = NULL;
> 
> The struct is zeroed out so initializing the handler is not necessary.
> 
> > 
> >      return 0;
> > 
> >   fail_add:
> > +    ASSERT(!hvm_ioreq_is_internal(id));
> >      hvm_ioreq_server_remove_all_vcpus(s);
> >      hvm_ioreq_server_unmap_pages(s);
> > 
> 
> I think it would be worthwhile having that ASSERT repeated in the called functions, and other functions that only operate on external ioreq servers e.g. hvm_ioreq_server_add_vcpu(), hvm_ioreq_server_map_pages(), etc. 

That's fine, but then I would also need to pass the ioreq server id to
those functions just to perform the ASSERT. I will leave those as-is
because I think passing the id just for that ASSERT is kind of
pointless.

> > @@ -864,20 +897,21 @@ int hvm_destroy_ioreq_server(struct domain *d, ioservid_t id)
> >          goto out;
> > 
> >      rc = -EPERM;
> > -    if ( s->emulator != current->domain )
> > +    /* NB: internal servers cannot be destroyed. */
> > +    if ( hvm_ioreq_is_internal(id) || s->emulator != current->domain )
> 
> Shouldn't the test of hvm_ioreq_is_internal(id) simply be an ASSERT? This function should only be called from a dm_op(), right?

Right, I think I've wrongly assumed this was also called when
destroying a domain, but domain destruction uses
hvm_destroy_all_ioreq_servers instead.

> >          goto out;
> > 
> >      domain_pause(d);
> > 
> >      p2m_set_ioreq_server(d, 0, id);
> > 
> > -    hvm_ioreq_server_disable(s);
> > +    hvm_ioreq_server_disable(s, hvm_ioreq_is_internal(id));
> > 
> >      /*
> >       * It is safe to call hvm_ioreq_server_deinit() prior to
> >       * set_ioreq_server() since the target domain is paused.
> >       */
> > -    hvm_ioreq_server_deinit(s);
> > +    hvm_ioreq_server_deinit(s, hvm_ioreq_is_internal(id));
> >      set_ioreq_server(d, id, NULL);
> > 
> >      domain_unpause(d);
> > @@ -909,7 +943,8 @@ int hvm_get_ioreq_server_info(struct domain *d, ioservid_t id,
> >          goto out;
> > 
> >      rc = -EPERM;
> > -    if ( s->emulator != current->domain )
> > +    /* NB: don't allow fetching information from internal ioreq servers. */
> > +    if ( hvm_ioreq_is_internal(id) || s->emulator != current->domain )
> 
> Again here, and several places below.

I've fixed the calls to hvm_get_ioreq_server_info,
hvm_get_ioreq_server_frame and hvm_map_mem_type_to_ioreq_server to
include an ASSERT that the passed ioreq is not internal.

Thanks, Roger.

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