Re: [RFC v2 02/11] tap: add die() on vhost error

On Wed, Jul 09, 2025 at 07:47:39PM +0200, Eugenio Pérez wrote:

In case the kernel needs to signal an error.

Signed-off-by: Eugenio Pérez

Reviewed-by: David Gibson

--- RFC v2: Add TODO (David)

Signed-off-by: Eugenio Pérez --- epoll_type.h | 2 ++ passt.c | 5 +++++ passt.h | 1 + tap.c | 16 ++++++++++++++++ 4 files changed, 24 insertions(+)

diff --git a/epoll_type.h b/epoll_type.h index 0371c14..93c4701 100644 --- a/epoll_type.h +++ b/epoll_type.h @@ -46,6 +46,8 @@ enum epoll_type { EPOLL_TYPE_REPAIR, /* vhost-kernel call socket */ EPOLL_TYPE_VHOST_CALL, + /* vhost-kernel error socket */ + EPOLL_TYPE_VHOST_ERROR,

EPOLL_NUM_TYPES, }; diff --git a/passt.c b/passt.c index 0f2659c..d839f5a 100644 --- a/passt.c +++ b/passt.c @@ -80,6 +80,7 @@ char *epoll_type_str[] = { [EPOLL_TYPE_REPAIR_LISTEN] = "TCP_REPAIR helper listening socket", [EPOLL_TYPE_REPAIR] = "TCP_REPAIR helper socket", [EPOLL_TYPE_VHOST_CALL] = "vhost-kernel call socket", + [EPOLL_TYPE_VHOST_ERROR] = "vhost-kernel error socket", }; static_assert(ARRAY_SIZE(epoll_type_str) == EPOLL_NUM_TYPES, "epoll_type_str[] doesn't match enum epoll_type"); @@ -362,6 +363,10 @@ loop: case EPOLL_TYPE_VHOST_CALL: tap_vhost_input(&c, ref, &now); break; + case EPOLL_TYPE_VHOST_ERROR: + /* TODO re-initialize vhost */ + die("Error on vhost-kernel socket"); + break; default: /* Can't happen */ ASSERT(0); diff --git a/passt.h b/passt.h index 7bb86c4..0066145 100644 --- a/passt.h +++ b/passt.h @@ -303,6 +303,7 @@ struct ctx { struct { int kick_fd; int call_fd; + int err_fd; } vq[2];

int no_dns; diff --git a/tap.c b/tap.c index e4a3822..0c49e6d 100644 --- a/tap.c +++ b/tap.c @@ -1598,6 +1598,22 @@ static int tap_ns_tun(void *arg) die_perror("Failed to add call eventfd to epoll"); } c->vq[i].call_fd = file.fd; + + file.fd = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC); + if (file.fd < 0) + die_perror("Failed to create error eventfd"); + + rc = ioctl(vhost_fd, VHOST_SET_VRING_ERR, &file); + if (rc < 0) + die_perror( + "VHOST_SET_VRING_ERR ioctl on /dev/vhost-net failed"); + + ref.type = EPOLL_TYPE_VHOST_ERROR, ref.fd = file.fd; + ev.data.u64 = ref.u64; + rc = epoll_ctl(c->epollfd, EPOLL_CTL_ADD, ref.fd, &ev); + if (rc < 0) + die_perror("Failed to add error eventfd to epoll"); + c->vq[i].err_fd = file.fd; }

/*

-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson