Re: [Xen-devel] [RFC PATCH 1/15]: PVH xen: turn gdb_frames/gdt_ents into union

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 24.01.13 at 15:29, Tim Deegan <tim@xxxxxxx> wrote:
> At 17:25 -0800 on 11 Jan (1357925122), Mukesh Rathor wrote:
>> diff -r bf249cd5f2c1 -r 278d7a933d88 xen/include/public/arch-x86/xen.h
>> --- a/xen/include/public/arch-x86/xen.h      Tue Oct 30 18:12:11 2012 +0000
>> +++ b/xen/include/public/arch-x86/xen.h      Fri Jan 11 16:19:40 2013 -0800
>> @@ -157,7 +157,16 @@ struct vcpu_guest_context {
>>      struct cpu_user_regs user_regs;         /* User-level CPU registers     
> */
>>      struct trap_info trap_ctxt[256];        /* Virtual IDT                  
> */
>>      unsigned long ldt_base, ldt_ents;       /* LDT (linear address, # ents) 
> */
>> -    unsigned long gdt_frames[16], gdt_ents; /* GDT (machine frames, # ents) 
> */
>> +    union {
>> +        struct {
>> +            /* GDT (machine frames, # ents) */
>> +            unsigned long gdt_frames[16], gdt_ents;
>> +        } pv;
>> +        struct {
>> +            /* PVH: GDTR addr and size */   
>> +            unsigned long gdtaddr, gdtsz;
> 
> The GDT size is always 16 bits; I'd be inclined to make the addr
> explicitly 64 bits too, to help out 32-bit toolstacks. 
> 
>> +        } pvh;
>> +    } u;
> 
> Also, would you consider renaming this as:
> 
>     union {
>         struct {
>             /* GDT (machine frames, # ents) */
>             unsigned long frames[16], ents;
>         } pv;
>         struct {
>             /* PVH: GDTR addr and size */   
>             unsigned long addr, sz;
>         } pvh;
>     } gdt;
> 
> ?  Then the calling code looks a little nicer. 

Did you overlook that it is a public header that gets modified
here?

Jan


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