> -----Original Message-----
> From: Jan Beulich <jbeul...@suse.com>
> Sent: 16 September 2020 15:43
> To: Paul Durrant <p...@xen.org>
> Cc: xen-devel@lists.xenproject.org; Durrant, Paul <pdurr...@amazon.co.uk>;
> Ian Jackson
> <ian.jack...@eu.citrix.com>; Wei Liu <w...@xen.org>; Andrew Cooper
> <andrew.coop...@citrix.com>; George
> Dunlap <george.dun...@citrix.com>; Julien Grall <jul...@xen.org>; Stefano
> Stabellini
> <sstabell...@kernel.org>
> Subject: RE: [EXTERNAL] [PATCH v8 6/8] common/domain: add a domain context
> record for shared_info...
>
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>
>
> On 15.09.2020 18:17, Paul Durrant wrote:
> > +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 )
> > + return rc;
> > +
> > + if ( i ) /* expect only a single instance */
> > + return -ENXIO;
> > +
> > + rc = domain_load_data(c, &ctxt, hdr_size);
> > + if ( rc )
> > + return rc;
> > +
> > + if ( ctxt.buffer_size > sizeof(shared_info_t) ||
> > + (ctxt.flags & ~DOMAIN_SAVE_32BIT_SHINFO) )
> > + return -EINVAL;
> > +
> > + if ( ctxt.flags & DOMAIN_SAVE_32BIT_SHINFO )
> > + {
> > +#ifdef CONFIG_COMPAT
> > + has_32bit_shinfo(d) = true;
> > +#else
> > + return -EINVAL;
> > +#endif
> > + }
> > +
> > + if ( is_pv_domain(d) )
> > + {
> > + shared_info_t *shinfo = xmalloc(shared_info_t);
> > +
> > + rc = domain_load_data(c, shinfo, sizeof(*shinfo));
>
> You need to check the allocation's success first.
Oops, yes.
> But of course the
> question is why you don't read directly into d->shared_info. The
> domain is paused at this point, isn't it?
>
It is, but domain_create() may have initialized something outside of the areas
we want to touch; I'm trying to follow what the existing restore code in
toolstack currently does.
> > + if ( rc )
> > + {
> > + xfree(shinfo);
> > + return rc;
> > + }
> > +
> > +#ifdef CONFIG_COMPAT
> > + if ( has_32bit_shinfo(d) )
> > + {
> > + memcpy(&d->shared_info->compat.vcpu_info,
> > + &shinfo->compat.vcpu_info,
> > + sizeof(d->shared_info->compat.vcpu_info));
> > + memcpy(&d->shared_info->compat.arch,
> > + &shinfo->compat.arch,
> > + sizeof(d->shared_info->compat.vcpu_info));
> > + memset(&d->shared_info->compat.evtchn_pending,
> > + 0,
> > + sizeof(d->shared_info->compat.evtchn_pending));
> > + memset(&d->shared_info->compat.evtchn_mask,
> > + 0xff,
> > + sizeof(d->shared_info->compat.evtchn_mask));
> > +
> > + d->shared_info->compat.arch.pfn_to_mfn_frame_list_list = 0;
> > + for ( i = 0; i < XEN_LEGACY_MAX_VCPUS; i++ )
> > + d->shared_info->compat.vcpu_info[i].evtchn_pending_sel = 0;
> > + }
> > + else
> > + {
> > + memcpy(&d->shared_info->native.vcpu_info,
> > + &shinfo->native.vcpu_info,
> > + sizeof(d->shared_info->native.vcpu_info));
> > + memcpy(&d->shared_info->native.arch,
> > + &shinfo->native.arch,
> > + sizeof(d->shared_info->native.arch));
> > + memset(&d->shared_info->native.evtchn_pending,
> > + 0,
> > + sizeof(d->shared_info->compat.evtchn_pending));
> > + memset(&d->shared_info->native.evtchn_mask,
> > + 0xff,
> > + sizeof(d->shared_info->native.evtchn_mask));
> > +
> > + d->shared_info->native.arch.pfn_to_mfn_frame_list_list = 0;
> > + for ( i = 0; i < XEN_LEGACY_MAX_VCPUS; i++ )
> > + d->shared_info->native.vcpu_info[i].evtchn_pending_sel = 0;
> > + }
> > +#else
> > + memcpy(&d->shared_info->vcpu_info,
> > + &shinfo->vcpu_info,
> > + sizeof(d->shared_info->vcpu_info));
> > + memcpy(&d->shared_info->arch,
> > + &shinfo->arch,
> > + sizeof(d->shared_info->shared));
> > + memset(&d->shared_info->evtchn_pending,
> > + 0,
> > + sizeof(d->shared_info->evtchn_pending));
> > + memset(&d->shared_info->evtchn_mask,
> > + 0xff,
> > + sizeof(d->shared_info->evtchn_mask));
> > +
> > + d->shared_info.arch.pfn_to_mfn_frame_list_list = 0;
> > + for ( i = 0; i < XEN_LEGACY_MAX_VCPUS; i++ )
> > + d->shared_info.vcpu_info[i].evtchn_pending_sel = 0;
> > +#endif
>
> A lot of redundancy; maybe it gets better if indeed you stop reading
> into an intermediate buffer.
As I said above, I think it is better if I continue to use an intermediate
buffer but I'll see if I can add some macro magic to make this less verbose.
>
> > + xfree(shinfo);
> > +
> > + rc = domain_load_end(c, false);
> > + }
> > + else
> > + rc = domain_load_end(c, true);
>
> Perhaps at least a brief comment here wouldn't hurt regarding the
> needs (or lack thereof) for HVM / Arm?
>
Ok.
Paul
> Jan
