WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

RE: [Xen-devel] [PATCH 3/5] vtdt: Modify vlapic code to add vtdt support

To: Keir Fraser <keir@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH 3/5] vtdt: Modify vlapic code to add vtdt support
From: "Wei, Gang" <gang.wei@xxxxxxxxx>
Date: Tue, 14 Dec 2010 17:13:35 +0800
Accept-language: zh-CN, en-US
Acceptlanguage: zh-CN, en-US
Cc: Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>, "Wei, Gang" <gang.wei@xxxxxxxxx>
Delivery-date: Tue, 14 Dec 2010 01:15:50 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <C92CDFF3.CCB9%keir@xxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <F26D193E20BBDC42A43B611D1BDEDE7124EADAFCDE@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> <C92CDFF3.CCB9%keir@xxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: AcubPslPXD79XKNoRpanX8il5iAsXgAIq7U+AAF2X3AAARpTFgAAmehg
Thread-topic: [Xen-devel] [PATCH 3/5] vtdt: Modify vlapic code to add vtdt support
Keir Fraser wrote on 2010-12-14:
>>>> @@ -265,6 +265,7 @@ struct hvm_hw_lapic {
>>>>      uint64_t             apic_base_msr;
>>>>      uint32_t             disabled; /* VLAPIC_xx_DISABLED */
>>>>      uint32_t             timer_divisor;
>>>> +    uint64_t             tdt_msr;
>>>>  };
>>> 
>>> Is this backward compatible with old HVM save images?
>> 
>> I am not sure about this. If it isn't, would you accept to simply
>> add another data trunk for TDT msr?
> 
> That's Tim's call. I would personally prefer for Xen to accept
> truncated chunks, and extend them with sensible 'old save image' defaults, 
> such as all-zeroes.
> That would be a generic solution to this case which will be reusable
> in future, and avoid needlessly creating extra chunk types just for
> backward compatibility reasons.

Ok. Let's wait for Tim to answer the call.

I just found some code in xen/hvm/save.h: _hvm_check_entry()
    if ( type != d->typecode || len != d->length )
    {
        gdprintk(XENLOG_WARNING, 
                 "HVM restore mismatch: expected type %u length %u, "
                 "saw type %u length %u\n", type, len, d->typecode, d->length);
        return -1;
    }

So I am assuming it would not be backward compatible with old HVM save images.

Jimmy

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel