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Fri, 22 Sep 2017 13:28:48 +0800
From: "Tan, Jianfeng" <jianfeng.tan@intel.com>
To: "Yang, Yi Y" <yi.y.yang@intel.com>, "yliu@fridaylinux.org"
<yliu@fridaylinux.org>
CC: "dev@dpdk.org" <dev@dpdk.org>, "Yang, Yi Y" <yi.y.yang@intel.com>
Thread-Topic: [dpdk-dev] [PATCH] vhost: fix vhost_user_set_mem_table error
Thread-Index: AQHTMeuk/BFonpyJqEiChipL9cJPb6LAWVdw
Date: Fri, 22 Sep 2017 05:28:48 +0000
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Subject: Re: [dpdk-dev] [PATCH] vhost: fix vhost_user_set_mem_table error
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> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Yi Yang
> Sent: Wednesday, September 20, 2017 4:32 PM
> To: yliu@fridaylinux.org
> Cc: dev@dpdk.org; Yang, Yi Y
> Subject: [dpdk-dev] [PATCH] vhost: fix vhost_user_set_mem_table error
>=20
> Usually vhost_user message VHOST_USER_SET_MEM_TABLE
> is only sent out during initialization and only sent
> once, but it isn't so for memory hotplug and hotunplug
> , for that case, vhost_user message VHOST_USER_SET_MEM_TABLE
> will be resent with the old memory regions (not hotunplugged)
> and the new memory regions (hotplugged), so current
> vhost_user_set_mem_table implementation is wrong for
> memory hotplug and hotunplug case, it will free current
> memory regions and unmap hugepages no matter if they
> are be using or not and if they are memory regions which
> have been initialized and mapped in the previous vhost_user
> message VHOST_USER_SET_MEM_TABLE or not.
>=20
> This commit fixed this issue very well, it will keep them
> intact for those old memory region it will unmap those
> memroy regions if they have been hotunplugged, it will
> initialize the new hotplugged memory regions and map
> hugepages if they are hotplugged.
>=20
> vhost_user message VHOST_USER_SET_MEM_TABLE will include
> all the current effective memory regions, the hotunplugged
> memory regions won't be included in VHOST_USER_SET_MEM_TABLE,
> the hotplugged memroy regions will be included in
> VHOST_USER_SET_MEM_TABLE.
>=20
> This has been verified in OVS DPDK by memory hotplug and
> hotunplug in qemu.
>=20
> Signed-off-by: Yi Yang <yi.y.yang@intel.com>
> ---
> lib/librte_vhost/vhost_user.c | 72
> ++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 65 insertions(+), 7 deletions(-)
>=20
> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.=
c
> index ad2e8d3..1c475d1 100644
> --- a/lib/librte_vhost/vhost_user.c
> +++ b/lib/librte_vhost/vhost_user.c
> @@ -509,17 +509,43 @@ vhost_user_set_mem_table(struct virtio_net *dev,
> struct VhostUserMsg *pmsg)
> uint64_t mmap_size;
> uint64_t mmap_offset;
> uint64_t alignment;
> - uint32_t i;
> + uint32_t i, j;
> int fd;
>=20
> - if (dev->mem) {
> - free_mem_region(dev);
> - rte_free(dev->mem);
> - dev->mem =3D NULL;
> + /* Handle hot unplug case */
> + if (dev->mem && dev->mem->nregions) {
> + i =3D 0;
> + j =3D 0;
> + while ((i < memory.nregions) && (j < dev->mem->nregions))
> {
> + reg =3D &dev->mem->regions[j];
> + /* munmap this region if it is hot unplugged */
> + if (reg->guest_user_addr
> + !=3D memory.regions[i].userspace_addr) {
> + if (reg->host_user_addr) {
> + munmap(reg->mmap_addr, reg-
> >mmap_size);
> + close(reg->fd);
> + }
> + reg->guest_user_addr =3D 0;
> + j++;
> + } else {
> + i++;
> + j++;
> + }
> + }
The algorithm here could be problematic for hot plug. For example,
T0: we have two regions with address 1, 3.
T1: we add another region, 2, which makes the regions as 1, 2, 3.
1st iteration, 1 matches 1, i++, j++;
2nd iteration, 2 does not match 3, unmap 3, j++.
> +
> + /* munmap these regions because they have been hot
> unplugged */
> + for (; j < dev->mem->nregions; j++) {
> + reg =3D &dev->mem->regions[j];
> + if (reg->host_user_addr) {
> + munmap(reg->mmap_addr, reg-
> >mmap_size);
> + close(reg->fd);
> + }
> + reg->guest_user_addr =3D 0;
> + }
> }
>=20
> - dev->nr_guest_pages =3D 0;
> if (!dev->guest_pages) {
> + dev->nr_guest_pages =3D 0;
We cannot just move this line here, which results in a wrong nr_guest_pages=
if we do hot plug/unplug instead of initialization.
> dev->max_guest_pages =3D 8;
> dev->guest_pages =3D malloc(dev->max_guest_pages *
> sizeof(struct guest_page));
> @@ -532,7 +558,7 @@ vhost_user_set_mem_table(struct virtio_net *dev,
> struct VhostUserMsg *pmsg)
> }
> }
>=20
> - dev->mem =3D rte_zmalloc("vhost-mem-table", sizeof(struct
> rte_vhost_memory) +
> + dev->mem =3D rte_realloc(dev->mem, sizeof(struct
> rte_vhost_memory) +
> sizeof(struct rte_vhost_mem_region) * memory.nregions, 0);
> if (dev->mem =3D=3D NULL) {
> RTE_LOG(ERR, VHOST_CONFIG,
> @@ -546,6 +572,38 @@ vhost_user_set_mem_table(struct virtio_net *dev,
> struct VhostUserMsg *pmsg)
> fd =3D pmsg->fds[i];
> reg =3D &dev->mem->regions[i];
>=20
> + /* This region should be skipped if it is initialized before */
> + if (reg->guest_user_addr =3D=3D
> memory.regions[i].userspace_addr) {
Also problematic for hot unplug. For example,
T0: we have three regions, 1, 2, 3.
T1: remove region 2, with only 1, 3 left.
1st iteration, 1 matches 1, skip old region 1.
2nd iteration, 3 does not match 2, do the mmap.
> + alignment =3D get_blk_size(fd);
> + if (alignment =3D=3D (uint64_t)-1) {
> + RTE_LOG(ERR, VHOST_CONFIG,
> + "couldn't get hugepage size "
> + "through fstat\n");
> + goto err_mmap;
> + }
> + RTE_LOG(INFO, VHOST_CONFIG,
> + "guest memory region(old)"
> + " %u, size: 0x%" PRIx64 "\n"
> + "\t guest physical addr: 0x%" PRIx64 "\n"
> + "\t guest virtual addr: 0x%" PRIx64 "\n"
> + "\t host virtual addr: 0x%" PRIx64 "\n"
> + "\t mmap addr : 0x%" PRIx64 "\n"
> + "\t mmap size : 0x%" PRIx64 "\n"
> + "\t mmap align: 0x%" PRIx64 "\n"
> + "\t mmap off : 0x%" PRIx64 "\n",
> + i, reg->size,
> + reg->guest_phys_addr,
> + reg->guest_user_addr,
> + reg->host_user_addr,
> + (uint64_t)(uintptr_t)reg->mmap_addr,
> + reg->mmap_size,
> + alignment,
> + (uint64_t)(uintptr_t)reg->host_user_addr -
> + (uint64_t)(uintptr_t)reg-
> >mmap_addr
> + );
> + continue;
> + }
> +
> reg->guest_phys_addr =3D
> memory.regions[i].guest_phys_addr;
> reg->guest_user_addr =3D memory.regions[i].userspace_addr;
> reg->size =3D memory.regions[i].memory_size;
> --
> 2.1.0