Re: [dpdk-dev] [PATCH v4 11/19] vhost: introduce postcopy's advise message

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

On 10/08/2018 06:22 PM, Ilya Maximets wrote:
> On 08.10.2018 18:25, 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 | 49 +++++++++++++++++++++++++++++++++++
>>   lib/librte_vhost/vhost_user.h |  3 ++-
>>   3 files changed, 53 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 20f38267d..3cdd2af28 100644
>> --- a/lib/librte_vhost/vhost_user.c
>> +++ b/lib/librte_vhost/vhost_user.c
>> @@ -24,13 +24,19 @@
>>   #include <stdlib.h>
>>   #include <string.h>
>>   #include <unistd.h>
>> +#include <fcntl.h>
>> +#include <sys/ioctl.h>
>>   #include <sys/mman.h>
>>   #include <sys/types.h>
>>   #include <sys/stat.h>
>> +#include <sys/syscall.h>
>>   #include <assert.h>
>>   #ifdef RTE_LIBRTE_VHOST_NUMA
>>   #include <numaif.h>
>>   #endif
>> +#ifdef RTE_LIBRTE_VHOST_POSTCOPY
>> +#include <linux/userfaultfd.h>
>> +#endif
>>   
>>   #include <rte_common.h>
>>   #include <rte_malloc.h>
>> @@ -69,6 +75,7 @@ static const char *vhost_message_str[VHOST_USER_MAX] = {
>>   	[VHOST_USER_IOTLB_MSG]  = "VHOST_USER_IOTLB_MSG",
>>   	[VHOST_USER_CRYPTO_CREATE_SESS] = "VHOST_USER_CRYPTO_CREATE_SESS",
>>   	[VHOST_USER_CRYPTO_CLOSE_SESS] = "VHOST_USER_CRYPTO_CLOSE_SESS",
>> +	[VHOST_USER_POSTCOPY_ADVISE]  = "VHOST_USER_POSTCOPY_ADVISE",
>>   };
>>   
>>   /* The possible results of a message handling function */
>> @@ -130,6 +137,11 @@ vhost_backend_cleanup(struct virtio_net *dev)
>>   		close(dev->slave_req_fd);
>>   		dev->slave_req_fd = -1;
>>   	}
>> +
>> +	if (dev->postcopy_ufd >= 0) {
>> +		close(dev->postcopy_ufd);
>> +		dev->postcopy_ufd = -1;
>> +	}
>>   }
>>   
>>   /*
>> @@ -1508,6 +1520,42 @@ vhost_user_iotlb_msg(struct virtio_net **pdev, struct VhostUserMsg *msg,
>>   	return VH_RESULT_OK;
>>   }
>>   
>> +static int
>> +vhost_user_set_postcopy_advise(struct virtio_net **pdev,
>> +			struct VhostUserMsg *msg,
>> +			int main_fd __rte_unused)
>> +{
>> +	struct virtio_net *dev = *pdev;
>> +#ifdef RTE_LIBRTE_VHOST_POSTCOPY
>> +	struct uffdio_api api_struct;
>> +
>> +	dev->postcopy_ufd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
>> +
>> +	if (dev->postcopy_ufd == -1) {
>> +		RTE_LOG(ERR, VHOST_CONFIG, "Userfaultfd not available: %s\n",
>> +				strerror(errno));
>> +		return VH_RESULT_ERR;
>> +	}
>> +	api_struct.api = UFFD_API;
>> +	api_struct.features = 0;
>> +	if (ioctl(dev->postcopy_ufd, UFFDIO_API, &api_struct)) {
>> +		RTE_LOG(ERR, VHOST_CONFIG, "UFFDIO_API ioctl failure: %s\n",
>> +				strerror(errno));
>> +		close(dev->postcopy_ufd);
> 
> Need to clear dev->postcopy_ufd value to avoid accidental closing of some
> other fd on backend cleanup.


Good catch, it will be fixed in v5.

Thanks!
Maxime