> -----Original Message----- > From: Maxime Coquelin [mailto:maxime.coque...@redhat.com] > Sent: Wednesday, February 14, 2018 3:53 PM > To: Tan, Jianfeng; dev@dpdk.org; y...@fridaylinux.org; Bie, Tiwei; > vkapl...@redhat.com > Cc: sta...@dpdk.org; jfrei...@redhat.com > Subject: Re: [PATCH v2 2/3] vhost: protect dirty logging against logging base > change > > Hi Jianfeng, > > On 02/14/2018 03:03 AM, Tan, Jianfeng wrote: > > Hi Maxime, > > > > > > On 11/28/2017 6:06 PM, Maxime Coquelin wrote: > >> > >> > >> On 11/24/2017 07:08 PM, Maxime Coquelin wrote: > >>> When performing live-migration with multiple queue pairs, > >>> VHOST_USER_SET_LOG_BASE request is sent multiple times. > >>> > >>> If packets are being processed by the PMD threads, it is > >>> possible that they are setting bits in the dirty log map while > >>> its region is being unmapped by the vhost-user protocol thread. > >>> It results in the following crash: > >>> Thread 3 "lcore-slave-2" received signal SIGSEGV, Segmentation fault. > >>> [Switching to Thread 0x7f71ca495700 (LWP 32451)] > >>> 0x00000000004bfc8a in vhost_set_bit (addr=0x7f71cbe18432 <error: > >>> Cannot access memory at address 0x7f71cbe18432>, nr=1) at > >>> /home/max/projects/src/mainline/dpdk/lib/librte_vhost/vhost.h:267 > >>> 267 __sync_fetch_and_or_8(addr, (1U << nr)); > >>> > >>> We can see the vhost-user protocol thread just did the unmap of the > >>> dirty log region when it happens. > >>> > >>> This patch prevents this by introducing a RW lock to protect > >>> the log base. > >>> > >>> Fixes: 54f9e32305d4 ("vhost: handle dirty pages logging request") > >>> Cc: sta...@dpdk.org > >>> > >>> Signed-off-by: Maxime Coquelin <maxime.coque...@redhat.com> > >>> --- > >>> lib/librte_vhost/vhost.c | 2 ++ > >>> lib/librte_vhost/vhost.h | 14 +++++++++++--- > >>> lib/librte_vhost/vhost_user.c | 4 ++++ > >>> 3 files changed, 17 insertions(+), 3 deletions(-) > >>> > >> > >> By clarifying the vhost-user spec, we may be able to avoid this lock and > >> just ignore the subsequent SET_LOG_BASE requests once > >> VHOST_F_LOG_ALL feature bit is set. > >> > >> So let's just discard this series for now. > > > > I would assume this issue has been addressed by the per-queue lock patch > > from Victor, correct? > > Correct. > > > Besides, we really don't need multiple unmap/map for each vq. Would you > > think this shall be fixed in QEMU? > > Yes, I tihnk you are right it should be fixed in QEMU, so that it is > sent only for the first queue pair. > > But I didn't had time to work on it TBH.
Thank you for the confirmation. And it's not an urgent issue to fix anyway.