Re: [PATCH v3 2/9] virtio-gpu: hostmem

[Alex Bennée]

Antonio Caggiano <antonio.caggiano@collabora.com> writes:

> From: Gerd Hoffmann <kraxel@redhat.com>
>
> Use VIRTIO_GPU_SHM_ID_HOST_VISIBLE as id for virtio-gpu.
>
> Signed-off-by: Antonio Caggiano <antonio.caggiano@collabora.com>
> Acked-by: Michael S. Tsirkin <mst@redhat.com>
> ---
> v3: Formatting fixes
>
>  hw/display/virtio-gpu-pci.c    | 15 +++++++++++++++
>  hw/display/virtio-gpu.c        |  1 +
>  hw/display/virtio-vga.c        | 33 ++++++++++++++++++++++++---------
>  include/hw/virtio/virtio-gpu.h |  5 +++++
>  4 files changed, 45 insertions(+), 9 deletions(-)
>
> diff --git a/hw/display/virtio-gpu-pci.c b/hw/display/virtio-gpu-pci.c
> index 93f214ff58..2cbbacd7fe 100644
> --- a/hw/display/virtio-gpu-pci.c
> +++ b/hw/display/virtio-gpu-pci.c
> @@ -33,6 +33,21 @@ static void virtio_gpu_pci_base_realize(VirtIOPCIProxy 
> *vpci_dev, Error **errp)
>      DeviceState *vdev = DEVICE(g);
>      int i;
>  
> +    if (virtio_gpu_hostmem_enabled(g->conf)) {
> +        vpci_dev->msix_bar_idx = 1;
> +        vpci_dev->modern_mem_bar_idx = 2;
> +        memory_region_init(&g->hostmem, OBJECT(g), "virtio-gpu-hostmem",
> +                           g->conf.hostmem);
> +        pci_register_bar(&vpci_dev->pci_dev, 4,
> +                         PCI_BASE_ADDRESS_SPACE_MEMORY |
> +                         PCI_BASE_ADDRESS_MEM_PREFETCH |
> +                         PCI_BASE_ADDRESS_MEM_TYPE_64,
> +                         &g->hostmem);
> +        virtio_pci_add_shm_cap(vpci_dev, 4, 0, g->conf.hostmem,
> +                               VIRTIO_GPU_SHM_ID_HOST_VISIBLE);
> +    }
> +
> +    qdev_set_parent_bus(vdev, BUS(&vpci_dev->bus), errp);
>      virtio_pci_force_virtio_1(vpci_dev);
>      if (!qdev_realize(vdev, BUS(&vpci_dev->bus), errp)) {
>          return;
> diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
> index 20cc703dcc..506b3b8eef 100644
> --- a/hw/display/virtio-gpu.c
> +++ b/hw/display/virtio-gpu.c
> @@ -1424,6 +1424,7 @@ static Property virtio_gpu_properties[] = {
>                       256 * MiB),
>      DEFINE_PROP_BIT("blob", VirtIOGPU, parent_obj.conf.flags,
>                      VIRTIO_GPU_FLAG_BLOB_ENABLED, false),
> +    DEFINE_PROP_SIZE("hostmem", VirtIOGPU, parent_obj.conf.hostmem,
> 0),

I note we don't have a definition for -device virtio-gpu or
virtio-gpu-pci in the invocation section of the manual (missing from
qemu-options.hx). Given the growing complexity of the device perhaps we
need those options and perhaps a new section under:

  
https://qemu.readthedocs.io/en/latest/system/device-emulation.html#emulated-devices

to outline how virtio-gpu works and what these control knobs are for and
why they would be used.

>      DEFINE_PROP_END_OF_LIST(),
>  };
>  
> diff --git a/hw/display/virtio-vga.c b/hw/display/virtio-vga.c
> index 4dcb34c4a7..aa8d1ab993 100644
> --- a/hw/display/virtio-vga.c
> +++ b/hw/display/virtio-vga.c
> @@ -115,17 +115,32 @@ static void virtio_vga_base_realize(VirtIOPCIProxy 
> *vpci_dev, Error **errp)
>      pci_register_bar(&vpci_dev->pci_dev, 0,
>                       PCI_BASE_ADDRESS_MEM_PREFETCH, &vga->vram);
>  
> -    /*
> -     * Configure virtio bar and regions
> -     *
> -     * We use bar #2 for the mmio regions, to be compatible with stdvga.
> -     * virtio regions are moved to the end of bar #2, to make room for
> -     * the stdvga mmio registers at the start of bar #2.
> -     */
> -    vpci_dev->modern_mem_bar_idx = 2;
> -    vpci_dev->msix_bar_idx = 4;
>      vpci_dev->modern_io_bar_idx = 5;
>  
> +    if (!virtio_gpu_hostmem_enabled(g->conf)) {
> +        /*
> +         * Configure virtio bar and regions
> +         *
> +         * We use bar #2 for the mmio regions, to be compatible with stdvga.
> +         * virtio regions are moved to the end of bar #2, to make room for
> +         * the stdvga mmio registers at the start of bar #2.
> +         */
> +        vpci_dev->modern_mem_bar_idx = 2;
> +        vpci_dev->msix_bar_idx = 4;
> +    } else {
> +        vpci_dev->msix_bar_idx = 1;
> +        vpci_dev->modern_mem_bar_idx = 2;

modern_mem_bar_idx is the same for both legs so why move its setting and
comment out of the common path? There is no comment for why msix_bar_idx
moves between the two legs.

> +        memory_region_init(&g->hostmem, OBJECT(g), "virtio-gpu-hostmem",
> +                           g->conf.hostmem);
> +        pci_register_bar(&vpci_dev->pci_dev, 4,
> +                         PCI_BASE_ADDRESS_SPACE_MEMORY |
> +                         PCI_BASE_ADDRESS_MEM_PREFETCH |
> +                         PCI_BASE_ADDRESS_MEM_TYPE_64,
> +                         &g->hostmem);
> +        virtio_pci_add_shm_cap(vpci_dev, 4, 0, g->conf.hostmem,
> +                               VIRTIO_GPU_SHM_ID_HOST_VISIBLE);
> +    }
> +
>      if (!(vpci_dev->flags & VIRTIO_PCI_FLAG_PAGE_PER_VQ)) {
>          /*
>           * with page-per-vq=off there is no padding space we can use
> diff --git a/include/hw/virtio/virtio-gpu.h b/include/hw/virtio/virtio-gpu.h
> index 2e28507efe..eafce75b04 100644
> --- a/include/hw/virtio/virtio-gpu.h
> +++ b/include/hw/virtio/virtio-gpu.h
> @@ -102,12 +102,15 @@ enum virtio_gpu_base_conf_flags {
>      (_cfg.flags & (1 << VIRTIO_GPU_FLAG_DMABUF_ENABLED))
>  #define virtio_gpu_blob_enabled(_cfg) \
>      (_cfg.flags & (1 << VIRTIO_GPU_FLAG_BLOB_ENABLED))
> +#define virtio_gpu_hostmem_enabled(_cfg) \
> +    (_cfg.hostmem > 0)
>  
>  struct virtio_gpu_base_conf {
>      uint32_t max_outputs;
>      uint32_t flags;
>      uint32_t xres;
>      uint32_t yres;
> +    uint64_t hostmem;
>  };
>  
>  struct virtio_gpu_ctrl_command {
> @@ -131,6 +134,8 @@ struct VirtIOGPUBase {
>      int renderer_blocked;
>      int enable;
>  
> +    MemoryRegion hostmem;
> +
>      struct virtio_gpu_scanout scanout[VIRTIO_GPU_MAX_SCANOUTS];
>  
>      int enabled_output_bitmask;


-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro