Re: [Qemu-devel] [PATCH v1 1/2] vhost-user: support SET_MEM_TABLE waite the result of mmap

[Linhaifeng]

On 2015/2/10 16:46, Michael S. Tsirkin wrote:
> On Tue, Feb 10, 2015 at 01:48:12PM +0800, linhaifeng wrote:
>> From: Linhaifeng <address@hidden>
>>
>> Slave should reply to master and set u64 to 0 if
>> mmap all regions success otherwise set u64 to 1.
>>
>> Signed-off-by: Linhaifeng <address@hidden>
> 
> How does this work with existig slaves though?
> 

Slaves should work like this:

int set_mem_table(...)
{
    ....
    for (idx = 0, i = 0; idx < memory.nregions; idx++) {
        ....
        mem = mmap(..);
        if (MAP_FAILED == mem) {
                msg->msg.u64 = 1;
                msg->msg.size = MEMB_SIZE(VhostUserMsg, u64);
                return 1;
        }
    }

    ....

    msg->msg.u64 = 0;
    msg->msg.size = MEMB_SIZE(VhostUserMsg, u64);
    return 1;
}

If slaves not reply QEMU will always wait.

>> ---
>>  docs/specs/vhost-user.txt | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
>> index 650bb18..c96bf6b 100644
>> --- a/docs/specs/vhost-user.txt
>> +++ b/docs/specs/vhost-user.txt
>> @@ -171,6 +171,7 @@ Message types
>>        Id: 5
>>        Equivalent ioctl: VHOST_SET_MEM_TABLE
>>        Master payload: memory regions description
>> +      Slave payload: u64 (0:success >0:failed)
>>  
>>        Sets the memory map regions on the slave so it can translate the vring
>>        addresses. In the ancillary data there is an array of file descriptors
>> -- 
>> 1.7.12.4
>>
> 
> 

-- 
Regards,
Haifeng