On 25 Jun 2014, at 17:50, Michael S. Tsirkin <m...@redhat.com> wrote:
> On Wed, Jun 25, 2014 at 03:46:04PM +0000, Damjan Marion (damarion) wrote:
>>
>> On 25 Jun 2014, at 17:29, Michael S. Tsirkin <m...@redhat.com> wrote:
>>
>>> On Wed, Jun 25, 2014 at 02:57:52PM +0000, Damjan Marion (damarion) wrote:
>>>>
>>>> On 25 Jun 2014, at 16:27, Michael S. Tsirkin <m...@redhat.com> wrote:
>>>>
>>>>> On Wed, Jun 25, 2014 at 02:20:56PM +0000, Damjan Marion (damarion) wrote:
>>>>>>
>>>>>> On 25 Jun 2014, at 16:13, Nikolay Nikolaev
>>>>>> <n.nikol...@virtualopensystems.com> wrote:
>>>>>>
>>>>>>>>> - it will require changes on the user side also
>>>>>>>>
>>>>>>>> why would it?
>>>>>>>> format seems unchanged, right?
>>>>>>>
>>>>>>> yes, but it will happen that multiple regions have same FD so call to
>>>>>>> mmap()
>>>>>>> should look different, I’m still playing with this on user side...
>>>>>>> but then you shoudl somehow accumulate the sizes and send just a single
>>>>>>> fd, something along these lines.
>>>>>>
>>>>>> Yes, so I’m not very happy with that approach and looking if there is
>>>>>> better proposal,
>>>>>> or at least wider agreement how to address this issue.
>>>>>>
>>>>>> Damjan
>>>>>
>>>>> still not sure what the issue is ...
>>>>>
>>>>
>>>> No issue, just additional logic is needed on user side to calculate total
>>>> size of shared regions and call mmap() once per FD.
>>>>
>>>> Agree?
>>>
>>> why not just call it multiple times? AFAIK linux handles this just fine.
>>
>> I need to specify size when calling mmap(), so i need to run trough all
>> regions and sum sizes before calling mmap().
>
> You can map same file in many places.
> Just call mmap many times with offsets.
agree, but in that case I need to know offset, which i need to calculate by
finding 1st region in the list.
I.e. My regions are:
nregions: 4
region:
gpa = 0x100000000
size = 3221225472
ua = 0x2aab6ac00000
region:
gpa = 0xFFFC0000
size = 262144
ua = 0x7fc13d200000
region:
gpa = 0x0
size = 655360
ua = 0x2aaaaac00000
region:
gpa = 0xC0000
size = 3220439040
ua = 0x2aaaaacc0000
So, to calculate offset for 1st region I need to find region with GPA 0x0
which is region 3.
Offset for region 1 is 0x2aab6ac00000 - 0x2aaaaac00000 = 0xC0000000.
BTW Any idea what to do with region 2, it doesn’t look like the one belonging
to the same place, but qemu_get_ram_fd() returns same FD for it.
