From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Jan Beulich" <JBeulich@suse.com>
Subject: Re: [PATCH v3 07/32] xen/x86: fix arch_set_info_guest
 for HVM guests
Date: Thu, 23 Jul 2015 09:32:52 -0600
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Cc: Andrew Cooper <andrew.cooper3@citrix.com>, Ian Campbell <ian.campbell@citrix.com>, xen-devel@lists.xenproject.org
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>>> On 23.07.15 at 17:10, <roger.pau@citrix.com> wrote:
> IMHO introducing a new structure that gets rid of all the PV-only 
> fields seems like a good option:
> 
> struct vcpu_hvm_context {
> #define _VGCF_online                   5
> #define VGCF_online                    (1<<_VGCF_online)
>     uint32_t flags;                         /* VGCF_* flags                 
> */
>     struct cpu_hvm_user_regs user_regs;     /* User-level CPU registers     
> */
>     /* NB. User pagetable on x86/64 is placed in ctrlreg[1]. */
>     uint32_t ctrlreg[8];                    /* CR0-CR7 (control registers)  
> */
>     uint32_t debugreg[8];                   /* DB0-DB7 (debug registers)    
> */
> };
> 
> I'm also seriously considering getting rid of ctrlreg and debugreg.
> Since HVM VCPUs will always be started in 32bit flat mode, it doesn't
> make sense IMHO to have both the 32 and the 64 version of the 
> registers, so cpu_hvm_user_regs is always going to be:
> 
> struct cpu_hvm_user_regs {
>     uint32_t ebx;
>     uint32_t ecx;
>     uint32_t edx;
>     uint32_t esi;
>     uint32_t edi;
>     uint32_t ebp;
>     uint32_t eax;
>     uint32_t eip;
>     uint32_t esp;
>     uint32_t eflags;
>     uint16_t cs;
>     uint16_t ss;
>     uint16_t es;
>     uint16_t ds;
>     uint16_t fs;
>     uint16_t gs;
> };
> 
> We could however do something similar to what's done in ARM and have
> a union of both the 32 and the 64bit registers in case we want to
> start the vCPU in 64bit mode sometime in the future.

What you gave above is suitable only for VCPUOP_initialise afaict.
Did you intend this to be the case?

Jan