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Re: [PATCH v1 2/2] vhost: Remove vhost_backend_can_merge() callback
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From: |
Igor Mammedov |
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Subject: |
Re: [PATCH v1 2/2] vhost: Remove vhost_backend_can_merge() callback |
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Date: |
Tue, 7 Mar 2023 12:16:44 +0100 |
On Tue, 7 Mar 2023 11:25:48 +0100
Igor Mammedov <imammedo@redhat.com> wrote:
> On Thu, 16 Feb 2023 12:47:52 +0100
> David Hildenbrand <david@redhat.com> wrote:
>
> > Checking whether the memory regions are equal is sufficient: if they are
> > equal, then most certainly the contained fd is equal.
> sounds reasonable to me.
>
> >
> > The whole vhost-user memslot handling is suboptimal and overly
> > complicated. We shouldn't have to lookup a RAM memory regions we got
> > notified about in vhost_user_get_mr_data() using a host pointer. But that
>
> While on janitor duty can you fixup following?
>
> vhost_user_get_mr_data() -> memory_region_from_host ->
> -> qemu_ram_block_from_host()
> for qemu_ram_block_from_host doc comment seems to out of
> sync (ram_addr not longer exists)
>
> > requires a bigger rework -- especially an alternative vhost_set_mem_table()
> > backend call that simply consumes MemoryRegionSections.
>
> just skimming through usage of vhost_user_get_mr_data() it looks like
> we are first collecting MemoryRegionSection-s into tmp_sections
> then we do vhost_commit we convert then into vhost_memory_region list
> and the we are trying hard to convert addresses from the later
> to back to MemoryRegions we've lost during tmp_sections conversion
> all over the place.
>
> To me it looks like we should drop conversion to vhost_dev::mem
> and replace its usage with vhost_dev::mem_sections directly
> to get rid of data duplication and back and forth addr<->mr conversion.
>
> > For now, let's just drop vhost_backend_can_merge().
> >
> > Signed-off-by: David Hildenbrand <david@redhat.com>
>
> Reviewed-by: Igor Mammedov <imammedo@redhat.com>
>
> > ---
> > hw/virtio/vhost-user.c | 14 --------------
> > hw/virtio/vhost-vdpa.c | 1 -
> > hw/virtio/vhost.c | 6 +-----
> > include/hw/virtio/vhost-backend.h | 4 ----
> > 4 files changed, 1 insertion(+), 24 deletions(-)
> >
> > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> > index e68daa35d4..4bfaf559a7 100644
> > --- a/hw/virtio/vhost-user.c
> > +++ b/hw/virtio/vhost-user.c
> > @@ -2195,19 +2195,6 @@ static int vhost_user_migration_done(struct
> > vhost_dev *dev, char* mac_addr)
> > return -ENOTSUP;
> > }
> >
> > -static bool vhost_user_can_merge(struct vhost_dev *dev,
> > - uint64_t start1, uint64_t size1,
> > - uint64_t start2, uint64_t size2)
> > -{
> > - ram_addr_t offset;
> > - int mfd, rfd;
> > -
> > - (void)vhost_user_get_mr_data(start1, &offset, &mfd);
> > - (void)vhost_user_get_mr_data(start2, &offset, &rfd);
> > -
> > - return mfd == rfd;
> > -}
> > -
> > static int vhost_user_net_set_mtu(struct vhost_dev *dev, uint16_t mtu)
> > {
> > VhostUserMsg msg;
> > @@ -2704,7 +2691,6 @@ const VhostOps user_ops = {
> > .vhost_set_vring_enable = vhost_user_set_vring_enable,
> > .vhost_requires_shm_log = vhost_user_requires_shm_log,
> > .vhost_migration_done = vhost_user_migration_done,
> > - .vhost_backend_can_merge = vhost_user_can_merge,
> > .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,
> > diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> > index 542e003101..9ab7bc8718 100644
> > --- a/hw/virtio/vhost-vdpa.c
> > +++ b/hw/virtio/vhost-vdpa.c
> > @@ -1317,7 +1317,6 @@ const VhostOps vdpa_ops = {
> > .vhost_set_config = vhost_vdpa_set_config,
> > .vhost_requires_shm_log = NULL,
> > .vhost_migration_done = NULL,
> > - .vhost_backend_can_merge = NULL,
> > .vhost_net_set_mtu = NULL,
> > .vhost_set_iotlb_callback = NULL,
> > .vhost_send_device_iotlb_msg = NULL,
> > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> > index b7fb960fa9..9d8662aa98 100644
> > --- a/hw/virtio/vhost.c
> > +++ b/hw/virtio/vhost.c
> > @@ -733,11 +733,7 @@ static void vhost_region_add_section(struct vhost_dev
> > *dev,
> > size_t offset = mrs_gpa - prev_gpa_start;
> >
> > if (prev_host_start + offset == mrs_host &&
> > - section->mr == prev_sec->mr &&
> > - (!dev->vhost_ops->vhost_backend_can_merge ||
> > - dev->vhost_ops->vhost_backend_can_merge(dev,
another question, can it relly happen, i.e. having 2 abut memory sections
with the same memory region, is yes then when/why?
> > - mrs_host, mrs_size,
> > - prev_host_start, prev_size))) {
> > + section->mr == prev_sec->mr) {
> > uint64_t max_end = MAX(prev_host_end, mrs_host + mrs_size);
> > need_add = false;
> > prev_sec->offset_within_address_space =
> > diff --git a/include/hw/virtio/vhost-backend.h
> > b/include/hw/virtio/vhost-backend.h
> > index c5ab49051e..abf1601ba2 100644
> > --- a/include/hw/virtio/vhost-backend.h
> > +++ b/include/hw/virtio/vhost-backend.h
> > @@ -86,9 +86,6 @@ typedef int (*vhost_set_vring_enable_op)(struct vhost_dev
> > *dev,
> > typedef bool (*vhost_requires_shm_log_op)(struct vhost_dev *dev);
> > typedef int (*vhost_migration_done_op)(struct vhost_dev *dev,
> > char *mac_addr);
> > -typedef bool (*vhost_backend_can_merge_op)(struct vhost_dev *dev,
> > - uint64_t start1, uint64_t size1,
> > - uint64_t start2, uint64_t
> > size2);
> > typedef int (*vhost_vsock_set_guest_cid_op)(struct vhost_dev *dev,
> > uint64_t guest_cid);
> > typedef int (*vhost_vsock_set_running_op)(struct vhost_dev *dev, int
> > start);
> > @@ -160,7 +157,6 @@ typedef struct VhostOps {
> > vhost_set_vring_enable_op vhost_set_vring_enable;
> > vhost_requires_shm_log_op vhost_requires_shm_log;
> > vhost_migration_done_op vhost_migration_done;
> > - vhost_backend_can_merge_op vhost_backend_can_merge;
> > vhost_vsock_set_guest_cid_op vhost_vsock_set_guest_cid;
> > vhost_vsock_set_running_op vhost_vsock_set_running;
> > vhost_set_iotlb_callback_op vhost_set_iotlb_callback;
>