Re: [Xen-devel] [PATCH V2 2/7]: PVH: use native irq, enable callback, use HVM ring ops, ...

[Mukesh Rathor <mukesh.rathor@oracle.com>]

On Fri, 12 Oct 2012 09:52:17 +0100
Ian Campbell <Ian.Campbell@citrix.com> wrote:

> >  drivers/xen/cpu_hotplug.c            |    4 +++-
> >  drivers/xen/events.c                 |    9 ++++++++-
> >  drivers/xen/xenbus/xenbus_client.c   |    3 ++-
> >  7 files changed, 27 insertions(+), 8 deletions(-)
> > 
> > diff --git a/arch/x86/include/asm/xen/interface.h
> > b/arch/x86/include/asm/xen/interface.h index 555f94d..f11edb0 100644
> > --- a/arch/x86/include/asm/xen/interface.h
> > +++ b/arch/x86/include/asm/xen/interface.h
> > @@ -143,7 +143,13 @@ 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 {
> > +		/* PV: GDT (machine frames, # ents).*/
> > +		unsigned long gdt_frames[16], gdt_ents;
> > +	} s;
> > +	unsigned long gdtaddr, gdtsz;	    /* PVH: GDTR addr
> > and size */
> 
> I've pointed out a few times that I think this is wrong -- gdtaddr and
> gdtsz will overlap each other in the union. I'm not sure how it even
> works, unless the hypervisor is ignoring one or the other. You need:
> 
> union {
> 	struct {
> 		unsigned long gdt_frames[16], gdt_ents;
> 	} pv;
> 	struct {
> 		unsigned long gdtaddr, gdtsz;
> 	} pvh;
> } gdt;
> 
> (I've gone with naming the union gdt instead of u. You might want
> therefore to also drop the gdt prefix from the members?)

Is it worth it, I mean, making it a union. Would you be OK if I just
used gdt_frames[0] and gdt_ends for gdtaddr and size?

thanks
Mukesh