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Re: [PATCH] vhost-user: add separate memslot counter for vhost-user
From: |
Michael S. Tsirkin |
Subject: |
Re: [PATCH] vhost-user: add separate memslot counter for vhost-user |
Date: |
Thu, 27 Aug 2020 08:11:22 -0400 |
On Tue, Aug 11, 2020 at 09:43:43AM +0800, Jiajun Chen 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.
>
> Signed-off-by: Jiajun Chen <chenjiajun8@huawei.com>
> Signed-off-by: Jianjay Zhou <jianjay.zhou@huawei.com>
cc a bunch more people
> ---
> hw/virtio/vhost-backend.c | 14 ++++++++
> hw/virtio/vhost-user.c | 28 ++++++++++++++++
> hw/virtio/vhost.c | 54 +++++++++++++++++++++++++------
> include/hw/virtio/vhost-backend.h | 5 +++
> include/hw/virtio/vhost.h | 1 +
> net/vhost-user.c | 7 ++++
> 6 files changed, 100 insertions(+), 9 deletions(-)
>
> diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
> index 782b1d67d9..35eec7e166 100644
> --- a/hw/virtio/vhost-backend.c
> +++ b/hw/virtio/vhost-backend.c
> @@ -20,6 +20,8 @@
> #include <linux/vhost.h>
> #include <sys/ioctl.h>
>
> +static unsigned int vhost_kernel_used_memslots;
> +
> static int vhost_kernel_call(struct vhost_dev *dev, unsigned long int
> request,
> void *arg)
> {
> @@ -238,6 +240,16 @@ 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)
> +{
> + vhost_kernel_used_memslots = dev->mem->nregions;
> +}
> +
> +static unsigned int vhost_kernel_get_used_memslots(void)
> +{
> + return vhost_kernel_used_memslots;
> +}
> +
> static const VhostOps kernel_ops = {
> .backend_type = VHOST_BACKEND_TYPE_KERNEL,
> .vhost_backend_init = vhost_kernel_init,
> @@ -269,6 +281,8 @@ 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..04d20fc3ee 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -232,6 +232,7 @@ static VhostUserMsg m __attribute__ ((unused));
>
> /* The version of the protocol we support */
> #define VHOST_USER_VERSION (0x1)
> +static unsigned int vhost_user_used_memslots;
>
> struct vhost_user {
> struct vhost_dev *dev;
> @@ -2354,6 +2355,31 @@ void vhost_user_cleanup(VhostUserState *user)
> user->chr = NULL;
> }
>
> +static void vhost_user_set_used_memslots(struct vhost_dev *dev)
> +{
> + unsigned int counter = 0;
> + int i;
> +
> + for (i = 0; i < dev->mem->nregions; ++i) {
> + struct vhost_memory_region *reg = dev->mem->regions + i;
> + ram_addr_t offset;
> + MemoryRegion *mr;
> +
> + assert((uintptr_t)reg->userspace_addr == reg->userspace_addr);
> + mr = memory_region_from_host((void *)(uintptr_t)reg->userspace_addr,
> + &offset);
> + if (mr && memory_region_get_fd(mr) > 0) {
> + counter++;
> + }
> + }
> + vhost_user_used_memslots = counter;
> +}
> +
> +static unsigned int vhost_user_get_used_memslots(void)
> +{
> + return vhost_user_used_memslots;
> +}
> +
> const VhostOps user_ops = {
> .backend_type = VHOST_BACKEND_TYPE_USER,
> .vhost_backend_init = vhost_user_backend_init,
> @@ -2387,4 +2413,6 @@ 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..7f36d7af25 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -45,20 +45,22 @@
> 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 used_memslots_exceeded;
> +
> 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->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 +504,6 @@ 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 +679,7 @@ 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 +695,17 @@ 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);
> @@ -1248,6 +1261,19 @@ static void vhost_virtqueue_cleanup(struct
> vhost_virtqueue *vq)
> event_notifier_cleanup(&vq->masked_notifier);
> }
>
> +static bool vhost_dev_used_memslots_is_exceeded(struct vhost_dev *hdev)
> +{
> + if (hdev->vhost_ops->vhost_get_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");
> + used_memslots_exceeded = true;
> + return true;
> + }
> + used_memslots_exceeded = false;
> + return false;
> +}
> +
> int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
> VhostBackendType backend_type, uint32_t busyloop_timeout)
> {
> @@ -1300,6 +1326,7 @@ 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 +1373,13 @@ 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,
> + * vhost_dev_used_memslots_is_exceeded will always return false for the
> + * first time vhost device hot-plug(vhost_get_used_memslots is always 0),
> + * so it needs to double check here
> + */
> + if (vhost_dev_used_memslots_is_exceeded(hdev)) {
> r = -1;
> if (busyloop_timeout) {
> goto fail_busyloop;
> @@ -1773,3 +1804,8 @@ int vhost_net_set_backend(struct vhost_dev *hdev,
>
> return -1;
> }
> +
> +bool used_memslots_is_exceeded(void)
> +{
> + return used_memslots_exceeded;
> +}
> diff --git a/include/hw/virtio/vhost-backend.h
> b/include/hw/virtio/vhost-backend.h
> index 8825bd278f..ed43a93692 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)(void);
> +
> 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..bf7cec445f 100644
> --- a/include/hw/virtio/vhost.h
> +++ b/include/hw/virtio/vhost.h
> @@ -144,4 +144,5 @@ int vhost_dev_set_inflight(struct vhost_dev *dev,
> struct vhost_inflight *inflight);
> int vhost_dev_get_inflight(struct vhost_dev *dev, uint16_t queue_size,
> struct vhost_inflight *inflight);
> +bool used_memslots_is_exceeded(void);
> #endif
> diff --git a/net/vhost-user.c b/net/vhost-user.c
> index 17532daaf3..2f0216b518 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 (used_memslots_is_exceeded()) {
> + error_report("used memslots exceeded the backend limit, quit "
> + "loop");
> + goto err;
> + }
> } while (!s->started);
>
> assert(s->vhost_net);
> --
> 2.27.0.dirty