On Thu, Jul 09, 2015 at 01:47:21PM +0200, Igor Mammedov wrote:
> QEMU asserts in vhost due to hitting vhost backend limit
> on number of supported memory regions.
>
> Describe all hotplugged memory as one continuos range
> to vhost with linear 1:1 HVA->GPA mapping in backend.
>
> Signed-off-by: Igor Mammedov <imamm...@redhat.com>
Hmm - a bunch of work here to recombine MRs that memory listener
interface breaks up. In particular KVM could benefit from this too (on
workloads that change the table a lot). Can't we teach memory core to
pass hva range as a single continuous range to memory listeners?
> ---
> hw/virtio/vhost.c | 47
> ++++++++++++++++++++++++++++++++++++++++++++---
> include/hw/virtio/vhost.h | 1 +
> 2 files changed, 45 insertions(+), 3 deletions(-)
>
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 2712c6f..7bc27f0 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -432,6 +432,10 @@ static void vhost_set_memory(MemoryListener *listener,
>
> assert(size);
>
> + if (!dev->rsvd_hva.mr) {
> + dev->rsvd_hva = memory_region_find_hva_range(section->mr);
> + }
> +
> /* Optimize no-change case. At least cirrus_vga does this a lot at this
> time. */
> ram = memory_region_get_ram_ptr(section->mr) +
> section->offset_within_region;
> if (add) {
> @@ -472,6 +476,42 @@ static void vhost_begin(MemoryListener *listener)
> dev->mem_changed_start_addr = -1;
> }
>
> +static int vhost_set_mem_table(struct vhost_dev *dev)
> +{
> + hwaddr start_addr = 0;
> + ram_addr_t size = 0;
> + struct vhost_memory *mem;
> + int r, i;
> +
> + /* drop memory ranges from continuos HVA */
> + mem = g_memdup(dev->mem, offsetof(struct vhost_memory, regions) +
> + dev->mem->nregions * sizeof dev->mem->regions[0]);
> + start_addr = dev->rsvd_hva.offset_within_address_space;
> + size = int128_get64(dev->rsvd_hva.size);
> + for (i = 0; i < mem->nregions; i++) {
> + if (mem->regions[i].guest_phys_addr >= start_addr &&
> + mem->regions[i].guest_phys_addr < start_addr + size) {
> + mem->nregions--;
> + memmove(&mem->regions[i], &mem->regions[i + 1],
> + (mem->nregions - i) * sizeof mem->regions[0]);
> + }
> + }
> + /* add one continuos HVA entry if memory ranges from it is present */
> + if (dev->mem->nregions > mem->nregions) {
> + struct vhost_memory_region *reg = &mem->regions[mem->nregions];
> +
> + reg->guest_phys_addr = start_addr;
> + reg->memory_size = size;
> + reg->userspace_addr =
> + (__u64)memory_region_get_ram_ptr(dev->rsvd_hva.mr);
> + mem->nregions++;
> + }
> +
> + r = dev->vhost_ops->vhost_call(dev, VHOST_SET_MEM_TABLE, mem);
> + g_free(mem);
> + return r;
> +}
> +
> static void vhost_commit(MemoryListener *listener)
> {
> struct vhost_dev *dev = container_of(listener, struct vhost_dev,
> @@ -500,7 +540,7 @@ static void vhost_commit(MemoryListener *listener)
> }
>
> if (!dev->log_enabled) {
> - r = dev->vhost_ops->vhost_call(dev, VHOST_SET_MEM_TABLE, dev->mem);
> + r = vhost_set_mem_table(dev);
> assert(r >= 0);
> dev->memory_changed = false;
> return;
> @@ -513,7 +553,7 @@ static void vhost_commit(MemoryListener *listener)
> if (dev->log_size < log_size) {
> vhost_dev_log_resize(dev, log_size + VHOST_LOG_BUFFER);
> }
> - r = dev->vhost_ops->vhost_call(dev, VHOST_SET_MEM_TABLE, dev->mem);
> + r = vhost_set_mem_table(dev);
> assert(r >= 0);
> /* To log less, can only decrease log size after table update. */
> if (dev->log_size > log_size + VHOST_LOG_BUFFER) {
> @@ -956,6 +996,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
> migrate_add_blocker(hdev->migration_blocker);
> }
> hdev->mem = g_malloc0(offsetof(struct vhost_memory, regions));
> + memset(&hdev->rsvd_hva, 0, sizeof hdev->rsvd_hva);
> hdev->n_mem_sections = 0;
> hdev->mem_sections = NULL;
> hdev->log = NULL;
> @@ -1119,7 +1160,7 @@ int vhost_dev_start(struct vhost_dev *hdev,
> VirtIODevice *vdev)
> if (r < 0) {
> goto fail_features;
> }
> - r = hdev->vhost_ops->vhost_call(hdev, VHOST_SET_MEM_TABLE, hdev->mem);
> + r = vhost_set_mem_table(hdev);
> if (r < 0) {
> r = -errno;
> goto fail_mem;
> diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
> index dd51050..d41bf2f 100644
> --- a/include/hw/virtio/vhost.h
> +++ b/include/hw/virtio/vhost.h
> @@ -40,6 +40,7 @@ struct vhost_dev {
> struct vhost_memory *mem;
> int n_mem_sections;
> MemoryRegionSection *mem_sections;
> + MemoryRegionSection rsvd_hva;
> struct vhost_virtqueue *vqs;
> int nvqs;
> /* the first virtqueue which would be used by this vhost dev */
> --
> 1.8.3.1
