From: Zachary Amsden <zamsden@redhat.com>
To: Glauber Costa <glommer@redhat.com>
Cc: Avi Kivity <avi@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Add Documentation/kvm/msr.txt
Date: Thu, 27 May 2010 10:13:12 -1000 [thread overview]
Message-ID: <4BFED258.40501@redhat.com> (raw)
In-Reply-To: <20100527160248.GF3445@mothafucka.localdomain>
On 05/27/2010 06:02 AM, Glauber Costa wrote:
> On Thu, May 27, 2010 at 11:15:43AM +0300, Avi Kivity wrote:
>
>> On 05/26/2010 09:04 PM, Glauber Costa wrote:
>>
>>> This patch adds a file that documents the usage of KVM-specific
>>> MSRs.
>>>
>>>
>> Looks good. A few comments:
>>
>>
>>> +
>>> +Custom MSR list
>>> +--------
>>> +
>>> +The current supported Custom MSR list is:
>>> +
>>> +MSR_KVM_WALL_CLOCK: 0x11
>>> +
>>> + data: physical address of a memory area.
>>>
>> Which must be in guest RAM (i.e., don't point it somewhere random
>> and expect the hypervisor to allocate it for you).
>>
>> Must be aligned to 4 bytes (we don't enforce it though).
>>
> I don't see the reason for it.
>
> If this is a requirement, our own implementation
> is failing to meet it.
>
It's so the atomic write actually is atomic. Stating a 4 -byte
alignment requirement prevents the wall clock from crossing a page boundary.
Zach
next prev parent reply other threads:[~2010-05-27 20:13 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-26 18:04 [PATCH] Add Documentation/kvm/msr.txt Glauber Costa
2010-05-26 18:35 ` Randy Dunlap
2010-05-26 18:59 ` Glauber Costa
2010-05-27 8:15 ` Avi Kivity
2010-05-27 16:02 ` Glauber Costa
2010-05-27 20:13 ` Zachary Amsden [this message]
2010-05-27 20:36 ` Glauber Costa
2010-05-27 21:02 ` Zachary Amsden
2010-05-28 0:10 ` Glauber Costa
2010-05-28 4:10 ` Zachary Amsden
2010-05-30 9:14 ` Avi Kivity
2010-05-31 13:49 ` Glauber Costa
2010-05-31 14:03 ` Avi Kivity
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