Hi Igor,
> -----Original Message-----
> From: Igor Mammedov [mailto:imamm...@redhat.com]
> Sent: Friday, December 29, 2017 5:31 PM
> To: Zhoujian (jay) <jianjay.z...@huawei.com>
> Cc: qemu-devel@nongnu.org; Huangweidong (C) <weidong.hu...@huawei.com>;
> m...@redhat.com; wangxin (U) <wangxinxin.w...@huawei.com>; Liuzhe (Cloud
> Open Labs, NFV) <gary.liu...@huawei.com>; Gonglei (Arei)
> <arei.gong...@huawei.com>
> Subject: Re: [Qemu-devel] [PATCH v3] vhost: add used memslot number for
> vhost-user and vhost-kernel separately
>
> On Fri, 29 Dec 2017 10:35:11 +0800
> Jay Zhou <jianjay.z...@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 hotplug a
> > new DIMM memory because vhost_has_free_slot just returned false,
> > however we can hotplug it safely in fact.
> >
> > Meanwhile, instead of asserting in vhost_user_set_mem_table(), error
> > number is used to gracefully prevent device to start. This fixed the
> > VM crash issue.
>
> below mostly style related comments,
> otherwise patch looks good to me
> >
> > Suggested-by: Igor Mammedov <imamm...@redhat.com>
> > Signed-off-by: Jay Zhou <jianjay.z...@huawei.com>
> > Signed-off-by: Zhe Liu <gary.liu...@huawei.com>
> > ---
> > hw/virtio/vhost-backend.c | 14 +++++++
> > hw/virtio/vhost-user.c | 84 +++++++++++++++++++++++++++++---
> -------
> > hw/virtio/vhost.c | 16 ++++----
> > include/hw/virtio/vhost-backend.h | 4 ++
> > 4 files changed, 91 insertions(+), 27 deletions(-)
> >
> > diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
> > index 7f09efa..866718c 100644
> > --- a/hw/virtio/vhost-backend.c
> > +++ b/hw/virtio/vhost-backend.c
> > @@ -15,6 +15,8 @@
> > #include "hw/virtio/vhost-backend.h"
> > #include "qemu/error-report.h"
> >
> > +static unsigned int vhost_kernel_used_memslots;
> > +
> > static int vhost_kernel_call(struct vhost_dev *dev, unsigned long int
> request,
> > void *arg) { @@ -233,6 +235,16 @@
> > 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, @@ -264,6 +276,8 @@
> > 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,
> > };
> >
> > int vhost_set_backend_type(struct vhost_dev *dev, VhostBackendType
> > backend_type) diff --git a/hw/virtio/vhost-user.c
> > b/hw/virtio/vhost-user.c index 093675e..0f913be 100644
> > --- a/hw/virtio/vhost-user.c
> > +++ b/hw/virtio/vhost-user.c
> > @@ -122,6 +122,8 @@ 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 {
> > CharBackend *chr;
> > int slave_fd;
> > @@ -289,12 +291,53 @@ static int vhost_user_set_log_base(struct
> vhost_dev *dev, uint64_t base,
> > return 0;
> > }
> >
> > +static int vhost_user_prepare_msg(struct vhost_dev *dev, VhostUserMsg
> *msg,
> > + int *fds) {
> > + int r = 0;
> > + int i, fd;
> > + size_t fd_num = 0;
> fd_num is redundant
> you can use msg->payload.memory.nregions as a counter
If using msg->payload.memory.nregions as a counter, referencing
the member of msg->payload.memory.regions will be like this:
msg->payload.memory.regions[msg->payload.memory.nregions].userspace_addr =
...
msg->payload.memory.regions[msg->payload.memory.nregions].memory_size = ...
which will make the line more longer...
>
> > +
> > + for (i = 0; i < dev->mem->nregions; ++i) {
> for (i = 0, msg->payload.memory.nregions = 0; ...
>
> > + 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);
> > + fd = memory_region_get_fd(mr);
> > + if (fd > 0) {
> > + if (fd_num < VHOST_MEMORY_MAX_NREGIONS) {
> instead of shifting below block to the right, I'd write it like this:
Without this patch, the number of characters for these two lines
msg.payload.memory.regions[fd_num].userspace_addr = reg->userspace_addr;
msg.payload.memory.regions[fd_num].guest_phys_addr =
reg->guest_phys_addr;
are more than 80 already...
>
> if (msg->payload.memory.nregions ==
> VHOST_MEMORY_MAX_NREGIONS) {
> return -1;
> }
msg->payload.memory.nregions as a counter for vhost-user setting mem table,
while fd_num as a counter for vhost_user_used_memslots, IIUC they can not be
merged into one counter.
If return -1 when
msg->payload.memory.nregions == VHOST_MEMORY_MAX_NREGIONS, the
vhost_user_used_memslots maybe not assigned correctly. fd_num should
be added by one if fd > 0 regardless of whether msg->payload.memory.nregions
equals to or larger than VHOST_MEMORY_MAX_NREGIONS.
Regards,
Jay
> > + msg->payload.memory.nregions++;
> > + msg->payload.memory.regions[fd_num].userspace_addr =
> > + reg->userspace_addr;
> > + msg->payload.memory.regions[fd_num].memory_size =
> > + reg->memory_size;
> > + msg->payload.memory.regions[fd_num].guest_phys_addr =
> > + reg-
> >guest_phys_addr;
> > + msg->payload.memory.regions[fd_num].mmap_offset =
> offset;
> > + fds[fd_num] = fd;
> > + } else {
> > + r = -1;
> > + }
> > + fd_num++;
> > + }
> > + }
> > +
> > + /* Save the number of memory slots available for vhost user,
> > + * vhost_user_get_used_memslots() can use it next time
> > + */
> > + vhost_user_used_memslots = fd_num;
> > +
> > + return r;
> > +}
> > +
> > static int vhost_user_set_mem_table(struct vhost_dev *dev,
> > struct vhost_memory *mem) {
> > int fds[VHOST_MEMORY_MAX_NREGIONS];
> > - int i, fd;
> > - size_t fd_num = 0;
> > + size_t fd_num;
> > bool reply_supported = virtio_has_feature(dev->protocol_features,
> >
> > VHOST_USER_PROTOCOL_F_REPLY_ACK);
> >
> > @@ -307,26 +350,12 @@ static int vhost_user_set_mem_table(struct
> vhost_dev *dev,
> > msg.flags |= VHOST_USER_NEED_REPLY_MASK;
> > }
> >
> > - 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);
> > - fd = memory_region_get_fd(mr);
> > - if (fd > 0) {
> > - msg.payload.memory.regions[fd_num].userspace_addr = reg-
> >userspace_addr;
> > - msg.payload.memory.regions[fd_num].memory_size = reg-
> >memory_size;
> > - msg.payload.memory.regions[fd_num].guest_phys_addr = reg-
> >guest_phys_addr;
> > - msg.payload.memory.regions[fd_num].mmap_offset = offset;
> > - assert(fd_num < VHOST_MEMORY_MAX_NREGIONS);
> > - fds[fd_num++] = fd;
> > - }
> > + if (vhost_user_prepare_msg(dev, &msg, fds) < 0) {
> > + error_report("Failed preparing vhost-user memory table msg");
> > + return -1;
> > }
> >
> > - msg.payload.memory.nregions = fd_num;
> > + fd_num = msg.payload.memory.nregions;
> >
> > if (!fd_num) {
> > error_report("Failed initializing vhost-user memory map, "
> > @@ -922,6 +951,19 @@ static void vhost_user_set_iotlb_callback(struct
> vhost_dev *dev, int enabled)
> > /* No-op as the receive channel is not dedicated to IOTLB
> > messages. */ }
> >
> > +static void vhost_user_set_used_memslots(struct vhost_dev *dev) {
> > + int fds[VHOST_MEMORY_MAX_NREGIONS];
> > + VhostUserMsg msg;
> > +
> > + vhost_user_prepare_msg(dev, &msg, fds); }
> > +
> > +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_init, @@ -948,4 +990,6 @@
> > const VhostOps user_ops = {
> > .vhost_net_set_mtu = vhost_user_net_set_mtu,
> > .vhost_set_iotlb_callback = vhost_user_set_iotlb_callback,
> > .vhost_send_device_iotlb_msg =
> > vhost_user_send_device_iotlb_msg,
> > + .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
> > e4290ce..59a32e9 100644
> > --- a/hw/virtio/vhost.c
> > +++ b/hw/virtio/vhost.c
> > @@ -43,20 +43,21 @@
> > 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->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, @@ -606,7
> > +607,7 @@ static void vhost_set_memory(MemoryListener *listener,
> > dev->mem_changed_start_addr = MIN(dev->mem_changed_start_addr,
> start_addr);
> > dev->mem_changed_end_addr = MAX(dev->mem_changed_end_addr,
> start_addr + size - 1);
> > dev->memory_changed = true;
> > - used_memslots = dev->mem->nregions;
> > + dev->vhost_ops->vhost_set_used_memslots(dev);
> > }
> >
> > static bool vhost_section(MemoryRegionSection *section) @@ -1251,7
> > +1252,8 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
> > goto fail;
> > }
> >
> > - if (used_memslots > hdev->vhost_ops-
> >vhost_backend_memslots_limit(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");
> > r = -1;
> > diff --git a/include/hw/virtio/vhost-backend.h
> > b/include/hw/virtio/vhost-backend.h
> > index a7a5f22..19961b5 100644
> > --- a/include/hw/virtio/vhost-backend.h
> > +++ b/include/hw/virtio/vhost-backend.h
> > @@ -84,6 +84,8 @@ typedef void (*vhost_set_iotlb_callback_op)(struct
> vhost_dev *dev,
> > int enabled); typedef int
> > (*vhost_send_device_iotlb_msg_op)(struct vhost_dev *dev,
> > struct vhost_iotlb_msg
> > *imsg);
> > +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;
> > @@ -118,6 +120,8 @@ typedef struct VhostOps {
> > vhost_vsock_set_running_op vhost_vsock_set_running;
> > vhost_set_iotlb_callback_op vhost_set_iotlb_callback;
> > vhost_send_device_iotlb_msg_op vhost_send_device_iotlb_msg;
> > + vhost_set_used_memslots_op vhost_set_used_memslots;
> > + vhost_get_used_memslots_op vhost_get_used_memslots;
> > } VhostOps;
> >
> > extern const VhostOps user_ops;
