Re: [Qemu-devel] [PATCH v4 12/29] postcopy+vhost-user: Split set_mem_table for postcopy

["Marc-André Lureau" <marcandre.lureau@gmail.com>]

Hi

On Mon, Mar 12, 2018 at 10:57 AM, Peter Xu <peterx@redhat.com> wrote:
> On Thu, Mar 08, 2018 at 07:57:54PM +0000, Dr. David Alan Gilbert (git) wrote:
>> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>>
>> Split the set_mem_table routines in both qemu and libvhost-user
>> because the postcopy versions are going to be quite different
>> once changes in the later patches are added.

You could add that this does not introduce functional change.

>>
>> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>> ---
>>  contrib/libvhost-user/libvhost-user.c | 53 ++++++++++++++++++++++++
>>  hw/virtio/vhost-user.c                | 77 ++++++++++++++++++++++++++++++++++-
>>  2 files changed, 128 insertions(+), 2 deletions(-)
>>
>> diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-user/libvhost-user.c
>> index beec7695a8..4922b2c722 100644
>> --- a/contrib/libvhost-user/libvhost-user.c
>> +++ b/contrib/libvhost-user/libvhost-user.c
>> @@ -448,6 +448,55 @@ vu_reset_device_exec(VuDev *dev, VhostUserMsg *vmsg)
>>      return false;
>>  }
>>
>> +static bool
>> +vu_set_mem_table_exec_postcopy(VuDev *dev, VhostUserMsg *vmsg)
>> +{
>> +    int i;
>> +    VhostUserMemory *memory = &vmsg->payload.memory;
>> +    dev->nregions = memory->nregions;
>> +    /* TODO: Postcopy specific code */
>> +    DPRINT("Nregions: %d\n", memory->nregions);
>> +    for (i = 0; i < dev->nregions; i++) {
>> +        void *mmap_addr;
>> +        VhostUserMemoryRegion *msg_region = &memory->regions[i];
>> +        VuDevRegion *dev_region = &dev->regions[i];
>> +
>> +        DPRINT("Region %d\n", i);
>> +        DPRINT("    guest_phys_addr: 0x%016"PRIx64"\n",
>> +               msg_region->guest_phys_addr);
>> +        DPRINT("    memory_size:     0x%016"PRIx64"\n",
>> +               msg_region->memory_size);
>> +        DPRINT("    userspace_addr   0x%016"PRIx64"\n",
>> +               msg_region->userspace_addr);
>> +        DPRINT("    mmap_offset      0x%016"PRIx64"\n",
>> +               msg_region->mmap_offset);
>> +
>> +        dev_region->gpa = msg_region->guest_phys_addr;
>> +        dev_region->size = msg_region->memory_size;
>> +        dev_region->qva = msg_region->userspace_addr;
>> +        dev_region->mmap_offset = msg_region->mmap_offset;
>> +
>> +        /* We don't use offset argument of mmap() since the
>> +         * mapped address has to be page aligned, and we use huge
>> +         * pages.  */
>> +        mmap_addr = mmap(0, dev_region->size + dev_region->mmap_offset,
>> +                         PROT_READ | PROT_WRITE, MAP_SHARED,
>> +                         vmsg->fds[i], 0);
>> +
>> +        if (mmap_addr == MAP_FAILED) {
>> +            vu_panic(dev, "region mmap error: %s", strerror(errno));
>> +        } else {
>> +            dev_region->mmap_addr = (uint64_t)(uintptr_t)mmap_addr;
>> +            DPRINT("    mmap_addr:       0x%016"PRIx64"\n",
>> +                   dev_region->mmap_addr);
>> +        }
>> +
>> +        close(vmsg->fds[i]);
>> +    }
>> +
>> +    return false;
>> +}
>> +
>>  static bool
>>  vu_set_mem_table_exec(VuDev *dev, VhostUserMsg *vmsg)
>>  {
>> @@ -464,6 +513,10 @@ vu_set_mem_table_exec(VuDev *dev, VhostUserMsg *vmsg)
>>      }
>>      dev->nregions = memory->nregions;
>>
>> +    if (dev->postcopy_listening) {
>> +        return vu_set_mem_table_exec_postcopy(dev, vmsg);
>> +    }
>> +
>>      DPRINT("Nregions: %d\n", memory->nregions);
>>      for (i = 0; i < dev->nregions; i++) {
>>          void *mmap_addr;
>> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
>> index ee200f703e..311addc33b 100644
>> --- a/hw/virtio/vhost-user.c
>> +++ b/hw/virtio/vhost-user.c
>> @@ -340,15 +340,86 @@ static int vhost_user_set_log_base(struct vhost_dev *dev, uint64_t base,
>>      return 0;
>>  }
>>
>> +static int vhost_user_set_mem_table_postcopy(struct vhost_dev *dev,
>> +                                             struct vhost_memory *mem)
>> +{
>> +    int fds[VHOST_MEMORY_MAX_NREGIONS];
>> +    int i, fd;
>> +    size_t fd_num = 0;
>> +    bool reply_supported = virtio_has_feature(dev->protocol_features,
>> +                                              VHOST_USER_PROTOCOL_F_REPLY_ACK);
>> +    /* TODO: Add actual postcopy differences */
>> +    VhostUserMsg msg = {
>> +        .hdr.request = VHOST_USER_SET_MEM_TABLE,
>> +        .hdr.flags = VHOST_USER_VERSION,
>> +    };
>> +
>> +    if (reply_supported) {
>> +        msg.hdr.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;
>> +        }
>> +    }
>> +
>> +    msg.payload.memory.nregions = fd_num;
>> +
>> +    if (!fd_num) {
>> +        error_report("Failed initializing vhost-user memory map, "
>> +                     "consider using -object memory-backend-file share=on");
>> +        return -1;
>> +    }
>> +
>> +    msg.hdr.size = sizeof(msg.payload.memory.nregions);
>> +    msg.hdr.size += sizeof(msg.payload.memory.padding);
>> +    msg.hdr.size += fd_num * sizeof(VhostUserMemoryRegion);
>> +
>> +    if (vhost_user_write(dev, &msg, fds, fd_num) < 0) {
>> +        return -1;
>> +    }
>> +
>> +    if (reply_supported) {
>> +        return process_message_reply(dev, &msg);
>> +    }
>> +
>> +    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 i, fd;
>>      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);
>>
>> +    if (do_postcopy) {
>> +        /* Postcopy has enough differences that it's best done in it's own
>> +         * version
>> +         */
>> +        return vhost_user_set_mem_table_postcopy(dev, mem);
>> +    }
>> +
>>      VhostUserMsg msg = {
>>          .hdr.request = VHOST_USER_SET_MEM_TABLE,
>>          .hdr.flags = VHOST_USER_VERSION,
>> @@ -372,9 +443,11 @@ static int vhost_user_set_mem_table(struct vhost_dev *dev,
>>                  error_report("Failed preparing vhost-user memory table msg");
>>                  return -1;
>>              }
>> -            msg.payload.memory.regions[fd_num].userspace_addr = reg->userspace_addr;
>> +            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].guest_phys_addr =
>> +                reg->guest_phys_addr;
>
> I would still prefer to generalize things out as shared functions,
> since otherwise we are adding somehow duplicate codes, which is IMHO
> harder to maintain.  And even if to do the duplication, I would keep
> the original code untouched (so these newlines will still not be
> needed).
>
> But considering that the series has been there for a long time, I'll
> try to be less harsh...  And yes, I know it's a burden to maintain
> private trees and keep rebasing.
>
> Feel free to remove the newlines (so at least commit log of those
> lines won't be modified), and either way I'll offer mine:
>
> Reviewed-by: Peter Xu <peterx@redhat.com>

I have the same feeling as Peter, but otherwise no objection - we can
try to factorize again later if possible:

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>


>
> Thanks,
>
>>              msg.payload.memory.regions[fd_num].mmap_offset = offset;
>>              fds[fd_num++] = fd;
>>          }
>> --
>> 2.14.3
>>
>
> --
> Peter Xu
>



-- 
Marc-André Lureau