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

[Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>]

On Thu, 24 Jan 2013 14:29:32 +0000
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. 

Initially, I had it called gdt, but during code review of linux
patch (exact same change there), it was suggested to change it. Also,
I really dont' like field names likes "addr" or "sz". I really don't
wanna grep or cscope for them.

Thanks
Mukesh


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