Re: [PATCH] xen: change the sizes of fields in the HVM start info layout to be 64bits

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

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On Fri, 8 Apr 2016, Jan Beulich wrote:
> >>> On 08.04.16 at 17:47, <roger.pau@citrix.com> wrote:
> > At the moment the only consumer of this structure is x86, but other arches
> > might also use it, so make all the fields 64bits. On x86 Xen will still try
> > to place everything below the 4GiB boundary, but that might not be feasible
> > in other arches.
> > 
> > Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
> > Requested-by: Jan Beulich <jbeulich@suse.com>
> 
> I don't think I've asked for _all_ fields to be made 64-bit. In
> particular...
> 
> > --- a/tools/libxc/include/xc_dom.h
> > +++ b/tools/libxc/include/xc_dom.h
> > @@ -227,16 +227,16 @@ struct xc_dom_image {
> >   * be required in the future if there are alignment changes.
> >   */
> >  struct hvm_start_info {
> > -    uint32_t magic;             /* Contains the magic value 0x336ec578       */
> > -                                /* ("xEn3" with the 0x80 bit of the "E" set).*/
> > -    uint32_t version;           /* Version of this structure.                */
> > -    uint32_t flags;             /* SIF_xxx flags.                            */
> > -    uint32_t cmdline_paddr;     /* Physical address of the command line.     */
> > -    uint32_t nr_modules;        /* Number of modules passed to the kernel.   */
> > -    uint32_t modlist_paddr;     /* Physical address of an array of           */
> > -                                /* hvm_modlist_entry.                        */
> > -    uint32_t rsdp_paddr;        /* Physical address of the RSDP ACPI data    */
> > -                                /* structure.                                */
> > +    uint64_t magic;         /* Contains the magic value 0x746f6f62336ec578   */
> > +                            /* ("xEn3boot" with the 0x80 bit of the "E" set).*/
> > +    uint64_t version;       /* Version of this structure.                    */
> > +    uint64_t flags;         /* SIF_xxx flags.                                */
> 
> ... none of these 3 need to be 64-bit, nor ...
> 
> > +    uint64_t cmdline_paddr; /* Physical address of the command line.         */
> > +    uint64_t nr_modules;    /* Number of modules passed to the kernel.       */
> 
> ...  this one.
> 
> Nacked-by: Jan Beulich <jbeulich@suse.com>

I know, but I don't see any harm in them being 64bits, and then the layout 
is clearer IMHO.

Roger. 

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