Re: [PATCH v5 6/9] libxc: create unmapped initrd in domain builder if supported

[Juergen Gross <jgross@suse.com>]

On 30/11/15 11:51, Ian Campbell wrote:
> On Mon, 2015-11-30 at 11:47 +0100, Juergen Gross wrote:
>> On 30/11/15 11:34, Ian Campbell wrote:
>>> On Mon, 2015-11-30 at 11:23 +0100, Juergen Gross wrote:
>>>> On 30/11/15 11:20, Wei Liu wrote:
>>>>> On Thu, Nov 26, 2015 at 08:35:02AM +0100, Juergen Gross wrote:
>>>>>>  
>>>>>>      /* initrd parameters as specified in start_info page */
>>>>>> -    unsigned long initrd_start;
>>>>>> -    unsigned long initrd_len;
>>>>>> +    uint64_t initrd_start;
>>>>>> +    uint64_t initrd_len;
>>>>>>  
>>>>>
>>>>> I think these should be of type xen_vaddr_t. Doesn't make a
>>>>> difference
>>>>> in the end though.
>>>>
>>>> xen_vaddr_t seems not to be appropriate. It can be either a virtual
>>>> address or a pfn.
>>>
>>> Did you mean a virtual address or a physical _address_? Potentially
>>> mixing
>>> addresses and frame numbers in a single variable seems liable to be
>>> confusing, at best.
>>
>> No, it's really a pfn. And this is part of the stable interface between
>> hypervisor and the pv-domU since more than 5 years now.
> 
> Including the virtual address bit?
> 
> That's a shame.

Before commit 9f41c22a559a7ec039a195f6dc8bca32c66fcd5a it could only be
a virtual address. This commit added the pfn possibility.

I think it was done via pfn rather than physical address as this would
enable the feature to be used for 32 bit domains as well without having
to limit the initrd position to the first 4 GB or having to change the
structure layout.


Juergen