Re: [Qemu-devel] [PATCH v2 1/2] vhost: add used memslot number for vhost-user and vhost-kernel separately

[Zhoujian (jay)]

Hi Igor,

> -----Original Message-----
> From: Igor Mammedov [mailto:imamm...@redhat.com]
> Sent: Saturday, December 23, 2017 3:03 AM
> To: Zhoujian (jay) <jianjay.z...@huawei.com>
> Cc: Huangweidong (C) <weidong.hu...@huawei.com>; m...@redhat.com; wangxin
> (U) <wangxinxin.w...@huawei.com>; qemu-devel@nongnu.org; Liuzhe (Cloud
> Open Labs, NFV) <gary.liu...@huawei.com>; dgilb...@redhat.com; Gonglei
> (Arei) <arei.gong...@huawei.com>
> Subject: Re: [Qemu-devel] [PATCH v2 1/2] vhost: add used memslot number
> for vhost-user and vhost-kernel separately
> 
> On Fri, 22 Dec 2017 17:25:13 +0100
> Igor Mammedov <imamm...@redhat.com> wrote:
> 
> > On Fri, 15 Dec 2017 16:45:54 +0800
> > Jay Zhou <jianjay.z...@huawei.com> wrote:
> [...]
> 
> > > +static void vhost_user_set_used_memslots(struct vhost_dev *dev) {
> > > +    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;
> > > +        int fd;
> > > +
> > > +        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) {
> > > +            counter++;
> > > +        }
> > > +    }
> > vhost_user_set_mem_table() already does the same counting, there is no
> > point in duplicating it, just drop vhost_set_used_memslots callback
> >
> > > +    vhost_user_used_memslots = counter;
> > and update this value from vhost_user_set_mem_table()
> never mind, updating it from vhost_user_set_mem_table() as it's called
> only when device is started which is not the case when backend is
> initialized, so the way you did it should work for both cases
> 

How about do it like this(not sure whether the best way, any idea?):

Define a new function, e.g.

static void vhost_user_set_used_memslots_and_msgs(struct vhost_dev *dev,
                            VhostUserMsg *msg, size_t *fd_num, int *fds)
{
    int num = 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;
        int fd;

        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 (msg && fd_num && fds) {
                msg->payload.memory.regions[num].userspace_addr
                                        = reg->userspace_addr;
                msg->payload.memory.regions[num].memory_size
                                        = reg->memory_size;
                msg->payload.memory.regions[num].guest_phys_addr
                                        = reg->guest_phys_addr;
                msg->payload.memory.regions[num].mmap_offset = offset;
                assert(num < VHOST_MEMORY_MAX_NREGIONS);
                fds[num++] = fd;
            }
        }
    }
    vhost_user_used_memslots = num;
    if (fd_num)
        *fd_num = num;
}

And call it when the backend is initialized and the device is started
respectively,

static void vhost_user_set_used_memslots(struct vhost_dev *dev)
{
        vhost_user_set_used_memslots_and_msgs(dev, NULL, NULL, NULL);
}

static int vhost_user_set_mem_table(struct vhost_dev *dev,
                                                struct vhost_memory *mem)
{
        [...]

        vhost_user_set_used_memslots_and_msgs(dev, &msg, &fd_num, fds);

        [...]
}


Regards,
Jay

> 
> >
> > > +}
> > > +
> [...]