From mboxrd@z Thu Jan  1 00:00:00 1970
From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: Re: [PATCH v10 09/20] x86/VPMU: Add public xenpmu.h
Date: Wed, 10 Sep 2014 13:23:23 -0400
Message-ID: <5410890B.9010900@oracle.com>
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To: Jan Beulich <JBeulich@suse.com>
Cc: tim@xen.org, kevin.tian@intel.com, keir@xen.org, suravee.suthikulpanit@amd.com, andrew.cooper3@citrix.com, eddie.dong@intel.com, xen-devel@lists.xen.org, Aravind.Gopalakrishnan@amd.com, jun.nakajima@intel.com
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On 09/10/2014 10:45 AM, Jan Beulich wrote:
>>>> On 04.09.14 at 05:41, <boris.ostrovsky@oracle.com> wrote:
>> +struct xen_pmu_arch {
>> +    union {
>> +        struct cpu_user_regs regs;
>> +        uint8_t pad[256];
>> +    } r;
> Can you remind me again what you need the union and padding for
> here?

This structure is laid out in a shared page with a (possibly 32-bit) 
guest who need to access fields that follow this union.

-boris