On Mon, 28 Sep 2020 21:17:31 +0800
Jiajun Chen <chenjiaj...@huawei.com> wrote:
> Used_memslots is equal to dev->mem->nregions now, it is true for
> vhost kernel, but not for vhost user, which uses the memory regions
> that have file descriptor. In fact, not all of the memory regions
> have file descriptor.
> It is usefully in some scenarios, e.g. used_memslots is 8, and only
> 5 memory slots can be used by vhost user, it is failed to hot plug
> a new memory RAM because vhost_has_free_slot just returned false,
> but we can hot plug it safely in fact.
I had an impression that all guest RAM has to be shared with vhost,
so combination of anon and fd based RAM couldn't work.
Am I wrong?
>
> --
> ChangeList:
> v3:
> -make used_memslots a member of struct vhost_dev instead of a global static
> value
it's global resource, so why?
>
> v2:
> -eliminating useless used_memslots_exceeded variable and
> used_memslots_is_exceeded() API
>
> v1:
> -vhost-user: add separate memslot counter for vhost-user
>
> Signed-off-by: Jiajun Chen <chenjiaj...@huawei.com>
> Signed-off-by: Jianjay Zhou <jianjay.z...@huawei.com>
> ---
> hw/virtio/vhost-backend.c | 12 ++++++++++
> hw/virtio/vhost-user.c | 25 +++++++++++++++++++++
> hw/virtio/vhost.c | 37 +++++++++++++++++++++++--------
> include/hw/virtio/vhost-backend.h | 5 +++++
> include/hw/virtio/vhost.h | 1 +
> net/vhost-user.c | 7 ++++++
> 6 files changed, 78 insertions(+), 9 deletions(-)
>
> diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
> index 782b1d67d9..7016f23ec5 100644
> --- a/hw/virtio/vhost-backend.c
> +++ b/hw/virtio/vhost-backend.c
> @@ -238,6 +238,16 @@ static void vhost_kernel_set_iotlb_callback(struct
> vhost_dev *dev,
> qemu_set_fd_handler((uintptr_t)dev->opaque, NULL, NULL, NULL);
> }
>
> +static void vhost_kernel_set_used_memslots(struct vhost_dev *dev)
> +{
> + dev->used_memslots = dev->mem->nregions;
> +}
> +
> +static unsigned int vhost_kernel_get_used_memslots(struct vhost_dev *dev)
> +{
> + return dev->used_memslots;
> +}
> +
> static const VhostOps kernel_ops = {
> .backend_type = VHOST_BACKEND_TYPE_KERNEL,
> .vhost_backend_init = vhost_kernel_init,
> @@ -269,6 +279,8 @@ static const VhostOps kernel_ops = {
> #endif /* CONFIG_VHOST_VSOCK */
> .vhost_set_iotlb_callback = vhost_kernel_set_iotlb_callback,
> .vhost_send_device_iotlb_msg = vhost_kernel_send_device_iotlb_msg,
> + .vhost_set_used_memslots = vhost_kernel_set_used_memslots,
> + .vhost_get_used_memslots = vhost_kernel_get_used_memslots,
> };
> #endif
>
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index 31231218dc..5dea64d8a8 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -2354,6 +2354,29 @@ void vhost_user_cleanup(VhostUserState *user)
> user->chr = NULL;
> }
>
> +static void vhost_user_set_used_memslots(struct vhost_dev *dev)
> +{
> + int i;
> + dev->used_memslots = 0;
> +
> + for (i = 0; i < dev->mem->nregions; ++i) {
> + struct vhost_memory_region *reg = dev->mem->regions + i;
> + ram_addr_t offset;
> + MemoryRegion *mr;
> + int fd;
> +
> + mr = vhost_user_get_mr_data(reg->userspace_addr, &offset, &fd);
> + if (mr && fd > 0) {
> + dev->used_memslots++;
> + }
> + }
> +}
> +
> +static unsigned int vhost_user_get_used_memslots(struct vhost_dev *dev)
> +{
> + return dev->used_memslots;
> +}
> +
> const VhostOps user_ops = {
> .backend_type = VHOST_BACKEND_TYPE_USER,
> .vhost_backend_init = vhost_user_backend_init,
> @@ -2387,4 +2410,6 @@ const VhostOps user_ops = {
> .vhost_backend_mem_section_filter = vhost_user_mem_section_filter,
> .vhost_get_inflight_fd = vhost_user_get_inflight_fd,
> .vhost_set_inflight_fd = vhost_user_set_inflight_fd,
> + .vhost_set_used_memslots = vhost_user_set_used_memslots,
> + .vhost_get_used_memslots = vhost_user_get_used_memslots,
> };
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 1a1384e7a6..98b967669b 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -45,20 +45,20 @@
> static struct vhost_log *vhost_log;
> static struct vhost_log *vhost_log_shm;
>
> -static unsigned int used_memslots;
> static QLIST_HEAD(, vhost_dev) vhost_devices =
> QLIST_HEAD_INITIALIZER(vhost_devices);
>
> bool vhost_has_free_slot(void)
> {
> - unsigned int slots_limit = ~0U;
> struct vhost_dev *hdev;
>
> QLIST_FOREACH(hdev, &vhost_devices, entry) {
> - unsigned int r = hdev->vhost_ops->vhost_backend_memslots_limit(hdev);
> - slots_limit = MIN(slots_limit, r);
> + if (hdev->vhost_ops->vhost_get_used_memslots(hdev) >=
> + hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) {
> + return false;
> + }
> }
> - return slots_limit > used_memslots;
> + return true;
> }
>
> static void vhost_dev_sync_region(struct vhost_dev *dev,
> @@ -502,7 +502,6 @@ static void vhost_commit(MemoryListener *listener)
> dev->n_mem_sections * sizeof dev->mem->regions[0];
> dev->mem = g_realloc(dev->mem, regions_size);
> dev->mem->nregions = dev->n_mem_sections;
> - used_memslots = dev->mem->nregions;
> for (i = 0; i < dev->n_mem_sections; i++) {
> struct vhost_memory_region *cur_vmr = dev->mem->regions + i;
> struct MemoryRegionSection *mrs = dev->mem_sections + i;
> @@ -678,6 +677,7 @@ static void vhost_region_add_section(struct vhost_dev
> *dev,
> dev->tmp_sections[dev->n_tmp_sections - 1].fv = NULL;
> memory_region_ref(section->mr);
> }
> + dev->vhost_ops->vhost_set_used_memslots(dev);
> }
>
> /* Used for both add and nop callbacks */
> @@ -693,6 +693,17 @@ static void vhost_region_addnop(MemoryListener *listener,
> vhost_region_add_section(dev, section);
> }
>
> +static void vhost_region_del(MemoryListener *listener,
> + MemoryRegionSection *section)
> +{
> + struct vhost_dev *dev = container_of(listener, struct vhost_dev,
> + memory_listener);
> + if (!vhost_section(dev, section)) {
> + return;
> + }
> + dev->vhost_ops->vhost_set_used_memslots(dev);
> +}
> +
> static void vhost_iommu_unmap_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
> {
> struct vhost_iommu *iommu = container_of(n, struct vhost_iommu, n);
> @@ -1300,6 +1311,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
> hdev->memory_listener = (MemoryListener) {
> .begin = vhost_begin,
> .commit = vhost_commit,
> + .region_del = vhost_region_del,
> .region_add = vhost_region_addnop,
> .region_nop = vhost_region_addnop,
> .log_start = vhost_log_start,
> @@ -1346,9 +1358,16 @@ int vhost_dev_init(struct vhost_dev *hdev, void
> *opaque,
> memory_listener_register(&hdev->memory_listener, &address_space_memory);
> QLIST_INSERT_HEAD(&vhost_devices, hdev, entry);
>
> - if (used_memslots > hdev->vhost_ops->vhost_backend_memslots_limit(hdev))
> {
> - error_report("vhost backend memory slots limit is less"
> - " than current number of present memory slots");
> + /*
> + * If we started a VM without any vhost device,
> + * for the first time vhost device hot-plug
> + * (vhost_get_used_memslots is always 0),
> + * so it needs to double check here.
> + */
> + if (hdev->vhost_ops->vhost_get_used_memslots(hdev) >
> + hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) {
> + error_report("vhost backend memory slots limit is less than"
> + " current number of present memory slots");
> r = -1;
> if (busyloop_timeout) {
> goto fail_busyloop;
> diff --git a/include/hw/virtio/vhost-backend.h
> b/include/hw/virtio/vhost-backend.h
> index 8825bd278f..6569c95a43 100644
> --- a/include/hw/virtio/vhost-backend.h
> +++ b/include/hw/virtio/vhost-backend.h
> @@ -124,6 +124,9 @@ typedef int (*vhost_get_device_id_op)(struct vhost_dev
> *dev, uint32_t *dev_id);
>
> typedef bool (*vhost_force_iommu_op)(struct vhost_dev *dev);
>
> +typedef void (*vhost_set_used_memslots_op)(struct vhost_dev *dev);
> +typedef unsigned int (*vhost_get_used_memslots_op)(struct vhost_dev *dev);
> +
> typedef struct VhostOps {
> VhostBackendType backend_type;
> vhost_backend_init vhost_backend_init;
> @@ -168,6 +171,8 @@ typedef struct VhostOps {
> vhost_vq_get_addr_op vhost_vq_get_addr;
> vhost_get_device_id_op vhost_get_device_id;
> vhost_force_iommu_op vhost_force_iommu;
> + vhost_set_used_memslots_op vhost_set_used_memslots;
> + vhost_get_used_memslots_op vhost_get_used_memslots;
> } VhostOps;
>
> extern const VhostOps user_ops;
> diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
> index 767a95ec0b..5ded21f86d 100644
> --- a/include/hw/virtio/vhost.h
> +++ b/include/hw/virtio/vhost.h
> @@ -90,6 +90,7 @@ struct vhost_dev {
> QLIST_HEAD(, vhost_iommu) iommu_list;
> IOMMUNotifier n;
> const VhostDevConfigOps *config_ops;
> + unsigned int used_memslots;
> };
>
> struct vhost_net {
> diff --git a/net/vhost-user.c b/net/vhost-user.c
> index 17532daaf3..7e93955537 100644
> --- a/net/vhost-user.c
> +++ b/net/vhost-user.c
> @@ -20,6 +20,7 @@
> #include "qemu/error-report.h"
> #include "qemu/option.h"
> #include "trace.h"
> +#include "include/hw/virtio/vhost.h"
>
> typedef struct NetVhostUserState {
> NetClientState nc;
> @@ -347,6 +348,12 @@ static int net_vhost_user_init(NetClientState *peer,
> const char *device,
> qemu_chr_fe_set_handlers(&s->chr, NULL, NULL,
> net_vhost_user_event, NULL, nc0->name, NULL,
> true);
> +
> + if (!vhost_has_free_slot()) {
> + error_report("used memslots exceeded the backend limit, quit "
> + "loop");
> + goto err;
> + }
> } while (!s->started);
>
> assert(s->vhost_net);
