Re: [Xen-devel] [Draft C] Boot ABI for HVM guests without a device-model

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Fri, 2015-09-04 at 09:21 -0600, Jan Beulich wrote:
> > 
> > > > On 04.09.15 at 16:31, <roger.pau@xxxxxxxxxx> wrote:
> > El 04/09/15 a les 16.08, Jan Beulich ha escrit:
> > > > > > On 04.09.15 at 14:11, <roger.pau@xxxxxxxxxx> wrote:
> > > > The format of the structure passed in the %ebx register is the 
> > > > following:
> > > 
> > > Even if it may sound like splitting hair: Please use precise wording. 
> > > It's
> > > not the structure that's contained in %ebx, but %ebx hold the address
> > > of that structure.
> > 
> > Would you be fine with replacing this sentence with:
> > 
> > The format of the boot start info structure is the following:
> 
> Yes (maybe insert "(pointed to be %ebx)").
> 
> > > > struct hvm_start_info {
> > > > #define HVM_START_MAGIC_VALUE 0x336ec578
> > > >     uint32_t magic;             /* Contains the magic value 
> > > > 0x336ec578       */
> > > >                                 /* ("xEn3" with the 0x80 bit of the 
> > > > "E" set).*/
> > > >     uint32_t flags;             /* SIF_xxx flags.                  
> > > >           */
> > > 
> > > Do really mean to re-use the SIF_* flags here?
> > 
> > We can introduce a new set of flags, HVM_INIT_*, which ATM is only 
> > going
> > to be:
> > 
> > #define HVM_FLAGS_INITDOMAIN (1<<0)
> 
> From an abstract pov I'd prefer that. Maybe I'm overlooking
> something which would be simplified by using the same values...
> 
> > > > AP startup
> > > > ==========
> > > > 
> > > > AP startup is performed using hypercalls. The following VCPU 
> > > > operations
> > > > are used in order to bring up secondary vCPUs:
> > > > 
> > > >  * VCPUOP_initialise is used to set the initial state of the vCPU. 
> > > > The
> > > >    argument passed to the hypercall must be of the type > > > > 
> > > > vcpu_hvm_context.
> > > 
> > > VCPUOP_initialise takes a struct vcpu_guest_context; I don't think
> > > we can or should change that.
> > 
> > Didn't we agree that vcpu_guest_context was not suitable for HVM/PVH 
> > guests?
> 
> Yes we did.
> 
> > Patch 24 of my HVM-without-dm series already introduces this new
> > structure and the necessary helpers.
> 
> I didn't look at most of the series yet (despite it already being at v6;
> I'm sorry, I just didn't get around so far). But I think you agree that
> we can't just change an existing hypercall. Iirc along with agreeing
> on vcpu_guest_context not being suitable we also agreed that this
> will need to be a new sub-op, and I wondered whether calling it
> VCPUOP_initialize would be too subtle.

You mean literally only s/s/z/? In which case, yes, far far to subtle.

Even initialise2 would be better than that alternative...

> 
> Jan
> 
> 
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