Re: [dpdk-dev] [04/12] vhost: introduce postcopy's advise message

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 09/28/2018 03:24 PM, Bruce Richardson wrote:
> On Fri, Sep 28, 2018 at 04:17:34PM +0300, Ilya Maximets wrote:
>> On 28.09.2018 15:13, Bruce Richardson wrote:
>>> On Fri, Sep 28, 2018 at 01:40:25PM +0300, Ilya Maximets wrote:
>>>> On 27.09.2018 11:28, Ilya Maximets wrote:
>>>>> On 26.09.2018 10:26, Maxime Coquelin wrote:
>>>>>> This patch opens a userfaultfd and sends it back to Qemu's
>>>>>> VHOST_USER_POSTCOPY_ADVISE request.
>>>>>>
>>>>>> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>>>>>> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>>>>>> ---
>>>>>>   lib/librte_vhost/vhost.h      |  2 ++
>>>>>>   lib/librte_vhost/vhost_user.c | 37 +++++++++++++++++++++++++++++++++++
>>>>>>   lib/librte_vhost/vhost_user.h |  3 ++-
>>>>>>   3 files changed, 41 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
>>>>>> index 25ffd7614..21722d8a8 100644
>>>>>> --- a/lib/librte_vhost/vhost.h
>>>>>> +++ b/lib/librte_vhost/vhost.h
>>>>>> @@ -363,6 +363,8 @@ struct virtio_net {
>>>>>>   	int			slave_req_fd;
>>>>>>   	rte_spinlock_t		slave_req_lock;
>>>>>>   
>>>>>> +	int			postcopy_ufd;
>>>>>> +
>>>>>>   	/*
>>>>>>   	 * Device id to identify a specific backend device.
>>>>>>   	 * It's set to -1 for the default software implementation.
>>>>>> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
>>>>>> index a9b429598..bdfe2cac0 100644
>>>>>> --- a/lib/librte_vhost/vhost_user.c
>>>>>> +++ b/lib/librte_vhost/vhost_user.c
>>>>>> @@ -24,9 +24,13 @@
>>>>>>   #include <stdlib.h>
>>>>>>   #include <string.h>
>>>>>>   #include <unistd.h>
>>>>>> +#include <fcntl.h>
>>>>>> +#include <linux/userfaultfd.h>
>>>>>
>>>>> Maybe we need compile time check for this header existence?
>>>>> Otherwise, this will bump minimal kernel version for default linux build
>>>>> to something like 4.3.
>>>>
>>>> We'll need a config option here (disabled by default) and guard all
>>>> the postcopy related code.
>>>> Meson build will be able to detect the header file and enable
>>>> the config if possible. Like this:
>>>>
>>>> lib/librte_vhost/meson.build:
>>>> if cc.has_header('linux/userfaultfd.h')
>>>>         dpdk_conf.set10('RTE_LIBRTE_VHOST_POSTCOPY', true)
>>>
>>> Are you sure you want 'set10' rather than 'set'. Set is probably easier
>>> because it ensures no define on false, while set10 has a define of 0. This
>>> has caught me out before.
>>>
>>> FYI, you can also avoid the if by putting the condition into the define:
>>>
>>> 	dpdk_conf.set('RTE_LIBRTE_VHOST_POSTCOPY', cc.has_header('...'))
>>
>> Sure, this variant looks better. Thanks for suggestions.
>> I just copied my version from the similar code for 'RTE_HAS_LIBNUMA'.
>>

Thanks Ilya & Bruce for the hint!
I'll do this in next version.

> Yes, looking at that code, it could do with a clean-up to shorten it too.
> [It's true that nothing embarasses a programmer more than their own code 6
> months layer :-)]

:)

Maxime
> /Bruce
>