Re: [Xen-devel] New Xen boot infrastructure proposal

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.05.13 at 16:09, Daniel Kiper <daniel.kiper@xxxxxxxxxx> wrote:
> On Tue, May 21, 2013 at 01:03:48PM +0100, Jan Beulich wrote:
>> >>> On 21.05.13 at 12:36, Daniel Kiper <daniel.kiper@xxxxxxxxxx> wrote:
>> > /* Xen Boot Info Arch (XBIA) memory map structure. */
>> > typedef struct {
>> >   /*
>> >    * Amount of lower memory accordingly to The Multiboot
>> >    * Specification version 0.6.96.
>> >    */
>> >   u32 lower;
>> >   /*
>> >    * Amount of upper memory accordingly to The Multiboot
>> >    * Specification version 0.6.96.
>> >    */
>> >   u32 upper;
>> >   u32 map_size;
>> >   struct e820entry *e820map;
>> > } xbia_mem_t;
>>
>> The concepts of lower, upper, and E820 memory are all very much
>> tied to x86.
> 
> That is why this is a part of Xen Boot Info Arch (XBIA)
> not Xen Boot Info (XBI) which is main struct.
> 
>> > /* Xen Boot Info Arch (XBIA). */
>> > typedef struct {
>> >   EFI_SYSTEM_TABLE *efi_system_table;
>> >   u64 mps; /* Pointer to MPS. */
>> >   u64 acpi; /* Pointer to ACPI RSDP. */
>> >   u64 smbios; /* Pointer to SMBIOS. */
>> >   xbia_mem_t mem;
>> >   struct xen_vga_console_info vga_console_info;
>> >   struct edd_info *edd_info;
>> > } xbia_t;
>>
>> As are - I think - MPS, EDD, perhaps SMBIOS, and maybe VGA.
> 
> As above.

Okay, emphasizing this would have helped, the more that the
split out xbia_mem_t suggested re-usability considerations.

>> the items above should become a separate one, in which case an
>> enumeration concept would likely be the better one.
> 
> I do not fully understand what do you mean by "enumeration concept".

That point is irrelevant with the above clarification.

> I think that passing info about system via many not "linked" variables
> is not the best idea. It works in that way today because multiboot
> structure is not extensible. That is why I think we should find new
> solution. Our new custom build structure which contains only stuff
> required by Xen looks good. All members are easliy accessible from C.
> It could be easliy extended (if we need it just add new member) because
> it would not be linked with specific boot protocol.

Why does  it matter whether the MBI structure is extensible?
Rather than copying everything around a number of times, we
can as well use is where it lives naturally. The only requirement
is that all information be accessible - whether in one strcture,
two, or a dozen doesn't matter.

Jan


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