On Wed, Mar 20, 2024 at 03:24:16PM +1000, Gavin Shan wrote: > > Before this patch was posted, I had debugging code to record last 16 transactions > to the available and used queue from guest and host side. It did reveal the wrong > head was fetched from the available queue. > > [ 11.785745] ================ virtqueue_get_buf_ctx_split ================ > [ 11.786238] virtio_net virtio0: output.0:id 74 is not a head! > [ 11.786655] head to be released: 036 077 > [ 11.786952] > [ 11.786952] avail_idx: > [ 11.787234] 000 63985 <-- > [ 11.787237] 001 63986 > [ 11.787444] 002 63987 > [ 11.787632] 003 63988 > [ 11.787821] 004 63989 > [ 11.788006] 005 63990 > [ 11.788194] 006 63991 > [ 11.788381] 007 63992 > [ 11.788567] 008 63993 > [ 11.788772] 009 63994 > [ 11.788957] 010 63995 > [ 11.789141] 011 63996 > [ 11.789327] 012 63997 > [ 11.789515] 013 63998 > [ 11.789701] 014 63999 > [ 11.789886] 015 64000 Does the error always occur at such a round idx value? Here, 64000 == 0xFA00. Maybe coincidence but it's improbable enough to be interesting. This debug code seems rather useful! -- Keir > [ 11.790068] > [ 11.790068] avail_head: > [ 11.790529] 000 075 <-- > [ 11.790718] 001 036 > [ 11.790890] 002 077 > [ 11.791061] 003 129 > [ 11.791231] 004 072 > [ 11.791400] 005 130 > [ 11.791574] 006 015 > [ 11.791748] 007 074 > [ 11.791918] 008 130 > [ 11.792094] 009 130 > [ 11.792263] 010 074 > [ 11.792437] 011 015 > [ 11.792617] 012 072 > [ 11.792788] 013 129 > [ 11.792961] 014 077 // The last two heads from guest to host: 077, 036 > [ 11.793134] 015 036 > > [root@nvidia-grace-hopper-05 qemu.main]# cat /proc/vhost > > avail_idx > 000 63998 > 001 64000 > 002 63954 <--- > 003 63955 > 004 63956 > 005 63974 > 006 63981 > 007 63984 > 008 63986 > 009 63987 > 010 63988 > 011 63989 > 012 63992 > 013 63993 > 014 63995 > 015 63997 > > avail_head > 000 074 > 001 015 > 002 072 > 003 129 > 004 074 // The last two heads seen by vhost is: 074, 036 > 005 036 > 006 075 <--- > 007 036 > 008 077 > 009 129 > 010 072 > 011 130 > 012 015 > 013 074 > 014 130 > 015 130 > > used_idx > 000 64000 > 001 63882 <--- > 002 63889 > 003 63891 > 004 63898 > 005 63936 > 006 63942 > 007 63946 > 008 63949 > 009 63953 > 010 63957 > 011 63981 > 012 63990 > 013 63992 > 014 63993 > 015 63999 > > used_head > 000 072 > 001 129 > 002 074 // The last two heads published to guest is: 074, 036 > 003 036 > 004 075 <--- > 005 036 > 006 077 > 007 129 > 008 072 > 009 130 > 010 015 > 011 074 > 012 130 > 013 130 > 014 074 > 015 015 > > Thanks, > Gavin > > > >
