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Re: [PATCH v2 3/3] Lift max memory slots limit imposed by vhost-user
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From: |
Raphael Norwitz |
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Subject: |
Re: [PATCH v2 3/3] Lift max memory slots limit imposed by vhost-user |
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Date: |
Sun, 9 Feb 2020 12:43:35 -0500 |
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User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Thu, Feb 06, 2020 at 03:32:38AM -0500, Michael S. Tsirkin wrote:
>
> On Wed, Jan 15, 2020 at 09:57:06PM -0500, Raphael Norwitz wrote:
> > The current vhost-user implementation in Qemu imposes a limit on the
> > maximum number of memory slots exposed to a VM using a vhost-user
> > device. This change provides a new protocol feature
> > VHOST_USER_F_CONFIGURE_SLOTS which, when enabled, lifts this limit and
> > allows a VM with a vhost-user device to expose a configurable number of
> > memory slots, up to the ACPI defined maximum. Existing backends which
> > do not support this protocol feature are unaffected.
>
> Hmm ACPI maximum seems to be up to 512 - is this too much to fit in a
> single message? So can't we just increase the number (after negotiating
> with remote) and be done with it, instead of add/remove? Or is there
> another reason to prefer add/remove?
>
As mentioned in my cover letter, we experimented with simply increasing the
message size and it didn’t work on our setup. We debugged down to the socket
layer and found that on the receiving end the messages were truncated at
around 512 bytes, or around 16 memory regions. To support 512 memory regions
we would need a message size of around 32 <bytes per region> * 512 <regions>
+ 8 <bytes for padding and region count> ~= 16k packet size. That would be 64
times larger than the next largest message size. We thought it would be cleaner
and more in line with the rest of the protocol to keep the message sizes
smaller. In particular, we thought memory regions should be treated like the
rings, which are sent over one message at a time instead of in one large
message.
Whether or not such a large message size can be made to work in our case,
separate messages will always work on Linux, and most likely all other UNIX
platforms QEMU is used on.
> >
> > This feature works by using three new messages,
> > VHOST_USER_GET_MAX_MEM_SLOTS, VHOST_USER_ADD_MEM_REG and
> > VHOST_USER_REM_MEM_REG. VHOST_USER_GET_MAX_MEM_SLOTS gets the
> > number of memory slots the backend is willing to accept when the
> > backend is initialized. Then, when the memory tables are set or updated,
> > a series of VHOST_USER_ADD_MEM_REG and VHOST_USER_REM_MEM_REG messages
> > are sent to transmit the regions to map and/or unmap instead of trying
> > to send all the regions in one fixed size VHOST_USER_SET_MEM_TABLE
> > message.
> >
> > The vhost_user struct maintains a shadow state of the VM’s memory
> > regions. When the memory tables are modified, the
> > vhost_user_set_mem_table() function compares the new device memory state
> > to the shadow state and only sends regions which need to be unmapped or
> > mapped in. The regions which must be unmapped are sent first, followed
> > by the new regions to be mapped in. After all the messages have been
> > sent, the shadow state is set to the current virtual device state.
> >
> > The current feature implementation does not work with postcopy migration
> > and cannot be enabled if the VHOST_USER_PROTOCOL_F_REPLY_ACK feature has
> > also been negotiated.
>
> Hmm what would it take to lift the restrictions?
> conflicting features like this makes is very hard for users to make
> an informed choice what to support.
>
We would need a setup with a backend which supports these features (REPLY_ACK
and postcopy migration). At first glance it looks like DPDK could work but
I'm not sure how easy it will be to test postcopy migration with the resources
we have.
> > Signed-off-by: Raphael Norwitz <address@hidden>
> > Signed-off-by: Peter Turschmid <address@hidden>
> > Suggested-by: Mike Cui <address@hidden>
> > ---
> > docs/interop/vhost-user.rst | 43 ++++++++
> > hw/virtio/vhost-user.c | 254
> > ++++++++++++++++++++++++++++++++++++++++----
> > 2 files changed, 275 insertions(+), 22 deletions(-)
> >
> > diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst
> > index 5f8b3a4..ae9acf2 100644
> > --- a/docs/interop/vhost-user.rst
> > +++ b/docs/interop/vhost-user.rst
> > @@ -786,6 +786,7 @@ Protocol features
> > #define VHOST_USER_PROTOCOL_F_HOST_NOTIFIER 11
> > #define VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD 12
> > #define VHOST_USER_PROTOCOL_F_RESET_DEVICE 13
> > + #define VHOST_USER_PROTOCOL_F_CONFIGURE_SLOTS 14
> >
> > Master message types
> > --------------------
> > @@ -1205,6 +1206,48 @@ Master message types
> > Only valid if the ``VHOST_USER_PROTOCOL_F_RESET_DEVICE`` protocol
> > feature is set by the backend.
> >
> > +``VHOST_USER_GET_MAX_MEM_SLOTS``
> > + :id: 35
> > + :equivalent ioctl: N/A
> > + :slave payload: u64
> > +
> > + When the VHOST_USER_PROTOCOL_F_CONFIGURE_SLOTS protocol feature has been
> > + successfully negotiated, this message is submitted by master to the
> > + slave. The slave should return the message with a u64 payload
> > + containing the maximum number of memory slots for QEMU to expose to
> > + the guest. This message is not supported with postcopy migration or if
> > + the VHOST_USER_PROTOCOL_F_REPLY_ACK feature has also been negotiated.
> > +
> > +``VHOST_USER_ADD_MEM_REG``
> > + :id: 36
> > + :equivalent ioctl: N/A
> > + :slave payload: memory region
> > +
> > + When the VHOST_USER_PROTOCOL_F_CONFIGURE_SLOTS protocol feature has been
> > + successfully negotiated, this message is submitted by master to the
> > slave.
> > + The message payload contains a memory region descriptor struct,
> > describing
> > + a region of guest memory which the slave device must map in. When the
> > + VHOST_USER_PROTOCOL_F_CONFIGURE_SLOTS protocol feature has been
> > successfully
> > + negotiated, along with the VHOST_USER_REM_MEM_REG message, this message
> > is
> > + used to set and update the memory tables of the slave device. This
> > message
> > + is not supported with postcopy migration or if the
> > + VHOST_USER_PROTOCOL_F_REPLY_ACK feature has also been negotiated.
> > +
> > +``VHOST_USER_REM_MEM_REG``
> > + :id: 37
> > + :equivalent ioctl: N/A
> > + :slave payload: memory region
> > +
> > + When the VHOST_USER_PROTOCOL_F_CONFIGURE_SLOTS protocol feature has been
> > + successfully negotiated, this message is submitted by master to the
> > slave.
> > + The message payload contains a memory region descriptor struct,
> > describing
> > + a region of guest memory which the slave device must unmap. When the
> > + VHOST_USER_PROTOCOL_F_CONFIGURE_SLOTS protocol feature has been
> > successfully
> > + negotiated, along with the VHOST_USER_ADD_MEM_REG message, this message
> > is
> > + used to set and update the memory tables of the slave device. This
> > message
> > + is not supported with postcopy migration or if the
> > + VHOST_USER_PROTOCOL_F_REPLY_ACK feature has also been negotiated.
> > +
> > Slave message types
> > -------------------
> >
> > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> > index af83fdd..fed6d02 100644
> > --- a/hw/virtio/vhost-user.c
> > +++ b/hw/virtio/vhost-user.c
> > @@ -35,11 +35,29 @@
> > #include <linux/userfaultfd.h>
> > #endif
> >
> > -#define VHOST_MEMORY_MAX_NREGIONS 8
> > +#define VHOST_MEMORY_LEGACY_NREGIONS 8
>
> Hardly legacy when this is intended to always be used e.g. with
> postcopy, right?
>
How about 'BASELINE'?
> > #define VHOST_USER_F_PROTOCOL_FEATURES 30
> > #define VHOST_USER_SLAVE_MAX_FDS 8
> >
> > /*
> > + * Set maximum number of RAM slots supported to
> > + * the maximum number supported by the target
> > + * hardware plaform.
> > + */
> > +#if defined(TARGET_X86) || defined(TARGET_X86_64) || \
> > + defined(TARGET_ARM) || defined(TARGET_ARM_64)
> > +#include "hw/acpi/acpi.h"
> > +#define VHOST_USER_MAX_RAM_SLOTS ACPI_MAX_RAM_SLOTS
> > +
> > +#elif defined(TARGET_PPC) || defined(TARGET_PPC_64)
> > +#include "hw/ppc/spapr.h"
> > +#define VHOST_USER_MAX_RAM_SLOTS SPAPR_MAX_RAM_SLOTS
> > +
> > +#else
> > +#define VHOST_USER_MAX_RAM_SLOTS 512
> > +#endif
> > +
> > +/*
> > * Maximum size of virtio device config space
> > */
> > #define VHOST_USER_MAX_CONFIG_SIZE 256
> > @@ -59,6 +77,7 @@ enum VhostUserProtocolFeature {
> > VHOST_USER_PROTOCOL_F_HOST_NOTIFIER = 11,
> > VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD = 12,
> > VHOST_USER_PROTOCOL_F_RESET_DEVICE = 13,
> > + VHOST_USER_PROTOCOL_F_CONFIGURE_SLOTS = 14,
> > VHOST_USER_PROTOCOL_F_MAX
> > };
> >
> > @@ -100,6 +119,9 @@ typedef enum VhostUserRequest {
> > VHOST_USER_SET_INFLIGHT_FD = 32,
> > VHOST_USER_GPU_SET_SOCKET = 33,
> > VHOST_USER_RESET_DEVICE = 34,
> > + VHOST_USER_GET_MAX_MEM_SLOTS = 35,
> > + VHOST_USER_ADD_MEM_REG = 36,
> > + VHOST_USER_REM_MEM_REG = 37,
> > VHOST_USER_MAX
> > } VhostUserRequest;
> >
> > @@ -121,9 +143,14 @@ typedef struct VhostUserMemoryRegion {
> > typedef struct VhostUserMemory {
> > uint32_t nregions;
> > uint32_t padding;
> > - VhostUserMemoryRegion regions[VHOST_MEMORY_MAX_NREGIONS];
> > + VhostUserMemoryRegion regions[VHOST_MEMORY_LEGACY_NREGIONS];
> > } VhostUserMemory;
> >
> > +typedef struct VhostUserMemRegMsg {
> > + uint32_t padding;
> > + VhostUserMemoryRegion region;
> > +} VhostUserMemRegMsg;
> > +
> > typedef struct VhostUserLog {
> > uint64_t mmap_size;
> > uint64_t mmap_offset;
> > @@ -182,6 +209,7 @@ typedef union {
> > struct vhost_vring_state state;
> > struct vhost_vring_addr addr;
> > VhostUserMemory memory;
> > + VhostUserMemRegMsg mem_reg;
> > VhostUserLog log;
> > struct vhost_iotlb_msg iotlb;
> > VhostUserConfig config;
> > @@ -210,7 +238,7 @@ struct vhost_user {
> > int slave_fd;
> > NotifierWithReturn postcopy_notifier;
> > struct PostCopyFD postcopy_fd;
> > - uint64_t postcopy_client_bases[VHOST_MEMORY_MAX_NREGIONS];
> > + uint64_t postcopy_client_bases[VHOST_USER_MAX_RAM_SLOTS];
> > /* Length of the region_rb and region_rb_offset arrays */
> > size_t region_rb_len;
> > /* RAMBlock associated with a given region */
> > @@ -222,6 +250,13 @@ struct vhost_user {
> >
> > /* True once we've entered postcopy_listen */
> > bool postcopy_listen;
> > +
> > + /* Maximum number of RAM slots supported by the backend */
> > + uint64_t memory_slots;
> > +
> > + /* Our current regions */
> > + int num_shadow_regions;
> > + VhostUserMemoryRegion shadow_regions[VHOST_USER_MAX_RAM_SLOTS];
> > };
> >
> > static bool ioeventfd_enabled(void)
> > @@ -370,7 +405,7 @@ int vhost_user_gpu_set_socket(struct vhost_dev *dev,
> > int fd)
> > static int vhost_user_set_log_base(struct vhost_dev *dev, uint64_t base,
> > struct vhost_log *log)
> > {
> > - int fds[VHOST_MEMORY_MAX_NREGIONS];
> > + int fds[VHOST_USER_MAX_RAM_SLOTS];
> > size_t fd_num = 0;
> > bool shmfd = virtio_has_feature(dev->protocol_features,
> > VHOST_USER_PROTOCOL_F_LOG_SHMFD);
> > @@ -429,7 +464,7 @@ static int vhost_user_fill_set_mem_table_msg(struct
> > vhost_user *u,
> > fd = memory_region_get_fd(mr);
> > if (fd > 0) {
> > if (postcopy) {
> > - assert(*fd_num < VHOST_MEMORY_MAX_NREGIONS);
> > + assert(*fd_num < VHOST_MEMORY_LEGACY_NREGIONS);
> > trace_vhost_user_set_mem_table_withfd(*fd_num, mr->name,
> > reg->memory_size,
> > reg->guest_phys_addr,
> > @@ -437,7 +472,7 @@ static int vhost_user_fill_set_mem_table_msg(struct
> > vhost_user *u,
> > offset);
> > u->region_rb_offset[i] = offset;
> > u->region_rb[i] = mr->ram_block;
> > - } else if (*fd_num == VHOST_MEMORY_MAX_NREGIONS) {
> > + } else if (*fd_num == VHOST_MEMORY_LEGACY_NREGIONS) {
> > error_report("Failed preparing vhost-user memory table
> > msg");
> > return -1;
> > }
> > @@ -474,7 +509,7 @@ static int vhost_user_set_mem_table_postcopy(struct
> > vhost_dev *dev,
> > struct vhost_memory *mem)
> > {
> > struct vhost_user *u = dev->opaque;
> > - int fds[VHOST_MEMORY_MAX_NREGIONS];
> > + int fds[VHOST_MEMORY_LEGACY_NREGIONS];
> > size_t fd_num = 0;
> > VhostUserMsg msg_reply;
> > int region_i, msg_i;
> > @@ -523,7 +558,7 @@ static int vhost_user_set_mem_table_postcopy(struct
> > vhost_dev *dev,
> > }
> >
> > memset(u->postcopy_client_bases, 0,
> > - sizeof(uint64_t) * VHOST_MEMORY_MAX_NREGIONS);
> > + sizeof(uint64_t) * VHOST_USER_MAX_RAM_SLOTS);
> >
> > /* They're in the same order as the regions that were sent
> > * but some of the regions were skipped (above) if they
> > @@ -564,18 +599,151 @@ static int vhost_user_set_mem_table_postcopy(struct
> > vhost_dev *dev,
> > return 0;
> > }
> >
> > +static inline bool reg_equal(VhostUserMemoryRegion *shadow_reg,
> > + struct vhost_memory_region *vdev_reg)
> > +{
> > + if (shadow_reg->guest_phys_addr == vdev_reg->guest_phys_addr &&
> > + shadow_reg->userspace_addr == vdev_reg->userspace_addr &&
> > + shadow_reg->memory_size == vdev_reg->memory_size) {
> > + return true;
> > + } else {
> > + return false;
> > + }
> > +}
> > +
> > +static int vhost_user_send_add_remove_regions(struct vhost_dev *dev,
> > + struct vhost_memory *mem,
> > + VhostUserMsg *msg)
> > +{
> > + struct vhost_user *u = dev->opaque;
> > + int i, j, fd;
> > + bool found[VHOST_USER_MAX_RAM_SLOTS] = {};
> > + bool matching = false;
> > + struct vhost_memory_region *reg;
> > + ram_addr_t offset;
> > + MemoryRegion *mr;
> > +
> > + /*
> > + * Ensure the VHOST_USER_PROTOCOL_F_REPLY_ACK has not been
> > + * negotiated and no postcopy migration is in progress.
> > + */
> > + assert(!virtio_has_feature(dev->protocol_features,
> > + VHOST_USER_PROTOCOL_F_REPLY_ACK));
> > + if (u->postcopy_listen && u->postcopy_fd.handler) {
> > + error_report("Postcopy migration is not supported when the "
> > + "VHOST_USER_PROTOCOL_F_CONFIGURE_SLOTS feature "
> > + "has been negotiated");
> > + return -1;
> > + }
> > +
> > + msg->hdr.size = sizeof(msg->payload.mem_reg.padding);
> > + msg->hdr.size += sizeof(VhostUserMemoryRegion);
> > +
> > + /*
> > + * Send VHOST_USER_REM_MEM_REG for memory regions in our shadow state
> > + * which are not found not in the device's memory state.
>
> double negation - could not parse this.
>
Apologies - typo here. It should say “Send VHOST_USER_REM_MEM_REG for memory
regions in our shadow state which are not found in the device's memory state.”
i.e. send messages to remove regions in the shadow state but not in the updated
device state.
> > + */
> > + for (i = 0; i < u->num_shadow_regions; ++i) {
> > + reg = dev->mem->regions;
> > +
> > + for (j = 0; j < dev->mem->nregions; j++) {
> > + reg = dev->mem->regions + j;
> > +
> > + assert((uintptr_t)reg->userspace_addr == reg->userspace_addr);
> > + mr = memory_region_from_host((void
> > *)(uintptr_t)reg->userspace_addr,
> > + &offset);
> > + fd = memory_region_get_fd(mr);
> > +
> > + if (reg_equal(&u->shadow_regions[i], reg)) {
> > + matching = true;
> > + found[j] = true;
> > + break;
> > + }
> > + }
> > +
> > + if (fd > 0 && !matching) {
> > + msg->hdr.request = VHOST_USER_REM_MEM_REG;
> > + msg->payload.mem_reg.region.userspace_addr =
> > reg->userspace_addr;
> > + msg->payload.mem_reg.region.memory_size = reg->memory_size;
> > + msg->payload.mem_reg.region.guest_phys_addr =
> > + reg->guest_phys_addr;
> > + msg->payload.mem_reg.region.mmap_offset = offset;
> > +
> > + if (vhost_user_write(dev, msg, &fd, 1) < 0) {
> > + return -1;
> > + }
> > + }
> > + }
> > +
> > + /*
> > + * Send messages to add regions present in the device which are not
> > + * in our shadow state.
> > + */
> > + for (i = 0; i < dev->mem->nregions; ++i) {
> > + reg = dev->mem->regions + i;
> > +
> > + /*
> > + * If the region was in both the shadow and vdev state we don't
> > + * need to send a VHOST_USER_ADD_MEM_REG message for it.
> > + */
> > + if (found[i]) {
> > + continue;
> > + }
> > +
> > + assert((uintptr_t)reg->userspace_addr == reg->userspace_addr);
> > + mr = memory_region_from_host((void
> > *)(uintptr_t)reg->userspace_addr,
> > + &offset);
> > + fd = memory_region_get_fd(mr);
> > +
> > + if (fd > 0) {
> > + msg->hdr.request = VHOST_USER_ADD_MEM_REG;
> > + msg->payload.mem_reg.region.userspace_addr =
> > reg->userspace_addr;
> > + msg->payload.mem_reg.region.memory_size = reg->memory_size;
> > + msg->payload.mem_reg.region.guest_phys_addr =
> > + reg->guest_phys_addr;
> > + msg->payload.mem_reg.region.mmap_offset = offset;
> > +
> > + if (vhost_user_write(dev, msg, &fd, 1) < 0) {
> > + return -1;
> > + }
> > + }
> > + }
> > +
> > + /* Make our shadow state match the updated device state. */
> > + u->num_shadow_regions = dev->mem->nregions;
> > + for (i = 0; i < dev->mem->nregions; ++i) {
> > + reg = dev->mem->regions + i;
> > + u->shadow_regions[i].guest_phys_addr = reg->guest_phys_addr;
> > + u->shadow_regions[i].userspace_addr = reg->userspace_addr;
> > + u->shadow_regions[i].memory_size = reg->memory_size;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > static int vhost_user_set_mem_table(struct vhost_dev *dev,
> > struct vhost_memory *mem)
> > {
> > struct vhost_user *u = dev->opaque;
> > - int fds[VHOST_MEMORY_MAX_NREGIONS];
> > + int fds[VHOST_MEMORY_LEGACY_NREGIONS];
> > size_t fd_num = 0;
> > bool do_postcopy = u->postcopy_listen && u->postcopy_fd.handler;
> > bool reply_supported = virtio_has_feature(dev->protocol_features,
> >
> > VHOST_USER_PROTOCOL_F_REPLY_ACK);
> > + bool config_slots =
> > + virtio_has_feature(dev->protocol_features,
> > + VHOST_USER_PROTOCOL_F_CONFIGURE_SLOTS);
> >
> > if (do_postcopy) {
> > - /* Postcopy has enough differences that it's best done in it's own
> > + if (config_slots) {
> > + error_report("Postcopy migration not supported with "
> > + "VHOST_USER_PROTOCOL_F_CONFIGURE_SLOTS feature "
> > + "enabled.");
> > + return -1;
> > + }
> > +
> > + /*
> > + * Postcopy has enough differences that it's best done in it's own
> > * version
> > */
> > return vhost_user_set_mem_table_postcopy(dev, mem);
> > @@ -589,17 +757,22 @@ static int vhost_user_set_mem_table(struct vhost_dev
> > *dev,
> > msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
> > }
> >
> > - if (vhost_user_fill_set_mem_table_msg(u, dev, &msg, fds, &fd_num,
> > - false) < 0) {
> > - return -1;
> > - }
> > -
> > - if (vhost_user_write(dev, &msg, fds, fd_num) < 0) {
> > - return -1;
> > - }
> > + if (config_slots && !reply_supported) {
> > + if (vhost_user_send_add_remove_regions(dev, mem, &msg) < 0) {
> > + return -1;
> > + }
> > + } else {
> > + if (vhost_user_fill_set_mem_table_msg(u, dev, &msg, fds, &fd_num,
> > + false) < 0) {
> > + return -1;
> > + }
> > + if (vhost_user_write(dev, &msg, fds, fd_num) < 0) {
> > + return -1;
> > + }
> >
> > - if (reply_supported) {
> > - return process_message_reply(dev, &msg);
> > + if (reply_supported) {
> > + return process_message_reply(dev, &msg);
> > + }
> > }
> >
> > return 0;
> > @@ -764,7 +937,7 @@ static int vhost_set_vring_file(struct vhost_dev *dev,
> > VhostUserRequest request,
> > struct vhost_vring_file *file)
> > {
> > - int fds[VHOST_MEMORY_MAX_NREGIONS];
> > + int fds[VHOST_USER_MAX_RAM_SLOTS];
> > size_t fd_num = 0;
> > VhostUserMsg msg = {
> > .hdr.request = request,
> > @@ -866,6 +1039,23 @@ static int vhost_user_get_features(struct vhost_dev
> > *dev, uint64_t *features)
> > return vhost_user_get_u64(dev, VHOST_USER_GET_FEATURES, features);
> > }
> >
> > +static int vhost_user_get_max_memslots(struct vhost_dev *dev,
> > + uint64_t *max_memslots)
> > +{
> > + uint64_t backend_max_memslots;
> > + int err;
> > +
> > + err = vhost_user_get_u64(dev, VHOST_USER_GET_MAX_MEM_SLOTS,
> > + &backend_max_memslots);
> > + if (err < 0) {
> > + return err;
> > + }
> > +
> > + *max_memslots = MIN(backend_max_memslots, VHOST_USER_MAX_RAM_SLOTS);
> > +
> > + return *max_memslots;
> > +}
> > +
> > static int vhost_user_set_owner(struct vhost_dev *dev)
> > {
> > VhostUserMsg msg = {
> > @@ -1439,6 +1629,24 @@ static int vhost_user_backend_init(struct vhost_dev
> > *dev, void *opaque)
> > "slave-req protocol features.");
> > return -1;
> > }
> > +
> > + /* get max memory regions if backend supports configurable RAM
> > slots */
> > + if (!virtio_has_feature(dev->protocol_features,
> > + VHOST_USER_PROTOCOL_F_CONFIGURE_SLOTS)) {
> > + u->memory_slots = VHOST_MEMORY_LEGACY_NREGIONS;
> > + } else if (virtio_has_feature(dev->protocol_features,
> > + VHOST_USER_PROTOCOL_F_REPLY_ACK)) {
> > + error_report("The VHOST_USER_PROTOCOL_F_CONFIGURE_SLOTS
> > protocol "
> > + "feature is not supported when the "
> > + "VHOST_USER_PROTOCOL_F_REPLY_ACK features has
> > also "
> > + "been negotiated");
> > + return -1;
> > + } else {
> > + err = vhost_user_get_max_memslots(dev, &u->memory_slots);
> > + if (err < 0) {
> > + return err;
> > + }
> > + }
> > }
> >
> > if (dev->migration_blocker == NULL &&
> > @@ -1502,7 +1710,9 @@ static int vhost_user_get_vq_index(struct vhost_dev
> > *dev, int idx)
> >
> > static int vhost_user_memslots_limit(struct vhost_dev *dev)
> > {
> > - return VHOST_MEMORY_MAX_NREGIONS;
> > + struct vhost_user *u = dev->opaque;
> > +
> > + return u->memory_slots;
> > }
> >
> > static bool vhost_user_requires_shm_log(struct vhost_dev *dev)
> > --
> > 1.8.3.1
>
>