Re: [PATCH] libxl, hvmloader: Don't relocate memory for MMIO hole

[George Dunlap <george.dunlap@eu.citrix.com>]

On 06/18/2013 01:46 PM, Hanweidong wrote:
>
>
>> -----Original Message-----
>> From: George Dunlap [mailto:george.dunlap@eu.citrix.com]
>> Sent: 2013年6月18日 20:21
>> To: Hanweidong
>> Cc: xen-devel@lists.xen.org; Ian Campbell; Ian Jackson; Stefano
>> Stabellini
>> Subject: Re: [PATCH] libxl,hvmloader: Don't relocate memory for MMIO
>> hole
>>
>> On 06/18/2013 01:18 PM, Hanweidong wrote:
>>>> -----Original Message-----
>>>> From: George Dunlap [mailto:george.dunlap@eu.citrix.com]
>>>> Sent: 2013年6月18日 0:49
>>>> To: George Dunlap
>>>> Cc: xen-devel@lists.xen.org; Ian Campbell; Ian Jackson; Stefano
>>>> Stabellini; Hanweidong
>>>> Subject: Re: [PATCH] libxl,hvmloader: Don't relocate memory for MMIO
>>>> hole
>>>>
>>>> On 17/06/13 17:43, George Dunlap wrote:
>>>>> At the moment, qemu-xen can't handle memory being relocated by
>>>>> hvmloader.  This may happen if a device with a large enough memory
>>>>> region is passed through to the guest.  At the moment, if this
>>>>> happens, then at some point in the future qemu will crash and the
>>>>> domain will hang.  (qemu-traditional is fine.)
>>>>>
>>>>> It's too late in the release to do a proper fix, so we try to do
>>>>> damage control.
>>>>>
>>>>> hvmloader already has mechanisms to relocate memory to 64-bit space
>>>>> if it can't make a big enough MMIO hole.  By default this is 2GiB;
>> if
>>>>> we just refuse to make the hole bigger if it will overlap with
>> guest
>>>>> memory, then this codepath will be taken by default.
>>>>>
>>>>> Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
>>>>> CC: Ian Campbell <ian.campbell@citrix.com>
>>>>> CC: Ian Jackson <ian.jackson@citrix.com>
>>>>> CC: Stefano Stabellini <stefano.stabellini@citrix.com>
>>>>> CC: Hanweidong <hanweidong@huawei.com>
>>>>
>>>> Unfortunatley, I don't have an easy way to test this, as all of the
>>>> devices on my system are far smaller than 256MiB.
>>>>
>>>> Weidong, could you give this patch a try and see if it works for you?
>>>>
>>>
>>> George，
>>>
>>> I don't have a system in hand to test it today. I try to have a test
>> tomorrow. In my experience, when it's prevented to relocate memory for
>> MMIO hole by your patch, windows guest will crash (blue screen) and
>> linux guest will hang with a blank display.
>>
>> You mean to say, you've tried this approach before (relocating to a
>> 64-bit MMIO region) and it doesn't work?
>
> I didn't try this approach. I missed you want to map mmio to 64-bit space instead of relocate memory. Currently only mmio size is larger than 512M (PCI_MIN_BIG_BAR_SIZE) will be map to 64-bit space. So you need to change the condition if you want to map smaller mmio to 64-bit space.

Ah, blast -- I forgot about that part.

Looks like the change will have to be bigger... :-(

  -George


_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel