Re: [Qemu-devel] vhost-user: broken mem regions

[Damjan Marion (damarion)]

On 25 Jun 2014, at 18:44, Paolo Bonzini <address@hidden> wrote:

>> nregions: 4
>> region:
>>      gpa = 0x100000000
>>      size = 3221225472
>>      ua = 0x2aab6ac00000
> 
> High memory, above 3 gigabytes.
> 
>> region:
>>      gpa = 0xFFFC0000
>>      size = 262144
>>      ua = 0x7fc13d200000
> 
> This is the BIOS.  There shouldn't be any FD for this one, it
> is not allocated in hugetlbfs.
> 
>> region:
>>      gpa = 0x0
>>      size = 655360
>>      ua = 0x2aaaaac00000
>> region:
>>      gpa = 0xC0000
>>      size = 3220439040
>>      ua = 0x2aaaaacc0000
> 
> Together, it's the first 3 GB of memory.
> 
> I understand now what you mean.  Yeah, the format should be changed
> to include the offset (why does vhost-user need the ua at all?
> perhaps the offset can replace the ua).
> 
>> 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.
> 
> This must be a bug.  I would have expected qemu_get_ram_fd to return -1
> here, so no descriptor should be passed to vhost-user.

Problem is inside qemu_get_ram_block():


    if (block && addr - block->offset < block->length) {
        goto found;
    }

this is true if we have > 4G of RAM allocated.

Any advice how to fix this?