On Thu, 23 Aug 2018 at 10:05, Burakov, Anatoly
<anatoly.bura...@intel.com> wrote:
>
> On 23-Aug-18 3:57 AM, Tiwei Bie wrote:
> > Deadlock can occur when allocating memory if a vhost-kernel
> > based virtio-user device is in use. Besides, it's possible
> > to have much more than 64 non-contiguous hugepage backed
> > memory regions due to the memory hotplug, which may cause
> > problems when handling VHOST_SET_MEM_TABLE request. A better
> > solution is to have the virtio-user pass all the VA ranges
> > reserved by DPDK to vhost-kernel.
> >
> > Bugzilla ID: 81
> > Fixes: 12ecb2f63b12 ("net/virtio-user: support memory hotplug")
> > Cc: sta...@dpdk.org
> >
> > Reported-by: Seán Harte <sea...@gmail.com>
> > Signed-off-by: Tiwei Bie <tiwei....@intel.com>
> > ---
> > drivers/net/virtio/virtio_user/vhost_kernel.c | 64 ++++++++-----------
> > 1 file changed, 27 insertions(+), 37 deletions(-)
> >
> > diff --git a/drivers/net/virtio/virtio_user/vhost_kernel.c
> > b/drivers/net/virtio/virtio_user/vhost_kernel.c
> > index b2444096c..49bd1b821 100644
> > --- a/drivers/net/virtio/virtio_user/vhost_kernel.c
> > +++ b/drivers/net/virtio/virtio_user/vhost_kernel.c
> > @@ -70,41 +70,12 @@ static uint64_t vhost_req_user_to_kernel[] = {
> > [VHOST_USER_SET_MEM_TABLE] = VHOST_SET_MEM_TABLE,
> > };
> >
> > -struct walk_arg {
> > - struct vhost_memory_kernel *vm;
> > - uint32_t region_nr;
> > -};
> > -static int
> > -add_memory_region(const struct rte_memseg_list *msl __rte_unused,
> > - const struct rte_memseg *ms, size_t len, void *arg)
> > -{
> > - struct walk_arg *wa = arg;
> > - struct vhost_memory_region *mr;
> > - void *start_addr;
> > -
> > - if (wa->region_nr >= max_regions)
> > - return -1;
> > -
> > - mr = &wa->vm->regions[wa->region_nr++];
> > - start_addr = ms->addr;
> > -
> > - mr->guest_phys_addr = (uint64_t)(uintptr_t)start_addr;
> > - mr->userspace_addr = (uint64_t)(uintptr_t)start_addr;
> > - mr->memory_size = len;
> > - mr->mmap_offset = 0;
> > -
> > - return 0;
> > -}
> > -
> > -/* By default, vhost kernel module allows 64 regions, but DPDK allows
> > - * 256 segments. As a relief, below function merges those virtually
> > - * adjacent memsegs into one region.
> > - */
> > static struct vhost_memory_kernel *
> > prepare_vhost_memory_kernel(void)
> > {
> > + struct rte_mem_config *mcfg = rte_eal_get_configuration()->mem_config;
> > struct vhost_memory_kernel *vm;
> > - struct walk_arg wa;
> > + uint32_t region_nr = 0, i;
> >
> > vm = malloc(sizeof(struct vhost_memory_kernel) +
> > max_regions *
> > @@ -112,15 +83,34 @@ prepare_vhost_memory_kernel(void)
> > if (!vm)
> > return NULL;
> >
> > - wa.region_nr = 0;
> > - wa.vm = vm;
> > + for (i = 0; i < RTE_MAX_MEMSEG_LISTS; i++) {
> > + struct rte_memseg_list *msl = &mcfg->memsegs[i];
> > + struct vhost_memory_region *mr;
> > + void *start_addr;
> > + uint64_t len;
>
> There is a rte_memseg_list_walk() - please do not iterate over memseg
> lists manually.
>
rte_memseg_list_walk() can't be used here because
prepare_vhost_memory_kernel() is sometimes called from a memory
callback. It will then hang trying to get a read lock on
memory_hotplug_lock.
I don't think the rte_memseg_list_walk_thread_unsafe() function is
appropriate because prepare_vhost_memory_kernel() may not always be
called from a memory callback.
> >
> > - if (rte_memseg_contig_walk(add_memory_region, &wa) < 0) {
> > - free(vm);
> > - return NULL;
> > + start_addr = msl->base_va;
> > + len = msl->page_sz * msl->memseg_arr.len;
> > +
> > + if (start_addr == NULL || len == 0)
> > + continue;
> > +
> > + if (region_nr >= max_regions) {
> > + free(vm);
> > + return NULL;
> > + }
> > +
> > + mr = &vm->regions[region_nr++];
> > + mr->guest_phys_addr = (uint64_t)(uintptr_t)start_addr;
> > + mr->userspace_addr = (uint64_t)(uintptr_t)start_addr;
> > + mr->memory_size = len;
> > + mr->mmap_offset = 0; /* flags_padding */
> > +
> > + PMD_DRV_LOG(DEBUG, "index=%u, addr=%p len=%" PRIu64,
> > + i, start_addr, len);
> > }
> >
> > - vm->nregions = wa.region_nr;
> > + vm->nregions = region_nr;
> > vm->padding = 0;
> > return vm;
> > }
> >
>
>
> --
> Thanks,
> Anatoly
