Re: [PATCH 02/10] xen: make GUEST_HANDLE_64() and uint64_aligned_t available everywhere

From: "Jan Beulich" <JBeulich@suse.com>
To: David Vrabel <david.vrabel@citrix.com>
Cc: Tim Deegan <tim@xen.org>, DanielKiper <daniel.kiper@oracle.com>,
	KeirFraser <keir@xen.org>, Ian Campbell <ian.campbell@citrix.com>,
	xen-devel@lists.xen.org
Subject: Re: [PATCH 02/10] xen: make GUEST_HANDLE_64() and uint64_aligned_t available everywhere
Date: Tue, 25 Jun 2013 16:02:47 +0100	[thread overview]
Message-ID: <51C9CD3702000078000E06C0@nat28.tlf.novell.com> (raw)
In-Reply-To: <51C9ADC9.6000705@citrix.com>

>>> On 25.06.13 at 16:48, David Vrabel <david.vrabel@citrix.com> wrote:
> I want the structure to be identical for 32-bit and 64-bit guests so
> compat code is not required in the hypervisor.
> 
> Without a macro like XEN_GUEST_HANDLE_64() how do you suggest the
> structure is defined so the field is sized correctly (i.e., 8 bytes)?
> 
> Are you suggesting something like?
> 
> typedef struct xen_kexec_load {
>     uint8_t  type;        /* One of KEXEC_TYPE_* */
>     uint8_t  _pad;
>     uint16_t arch;        /* ELF machine type (EM_*). */
>     uint32_t nr_segments;
>     union {
>         XEN_GUEST_HANDLE(xen_kexec_segment_t) segments;
>         uint64_t _qword;
>     } u;
>     uint64_t entry_maddr; /* image entry point machine address. */
> } xen_kexec_load_t;

Yes - there are already other cases similar to this in the public
headers, for example struct vcpu_register_runstate_memory_area
and struct vcpu_register_time_memory_area.

Jan