Re: [RFC QEMU PATCH 01/18] virtio: Add shared memory capability

[Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>]

On 12/3/23 10:22, Huang Rui wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx>
>
> Define a new capability type 'VIRTIO_PCI_CAP_SHARED_MEMORY_CFG' to allow
> defining shared memory regions with sizes and offsets of 2^32 and more.
> Multiple instances of the capability are allowed and distinguished
> by a device-specific 'id'.
>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@xxxxxxxxxx>
> Signed-off-by: Antonio Caggiano <antonio.caggiano@xxxxxxxxxxxxx>
> ---
>   hw/virtio/virtio-pci.c         | 18 ++++++++++++++++++
>   include/hw/virtio/virtio-pci.h |  4 ++++
>   2 files changed, 22 insertions(+)
>
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index a1c9dfa7bb..ae4c29cb96 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -1191,6 +1191,24 @@ static int virtio_pci_add_mem_cap(VirtIOPCIProxy *proxy,
>       return offset;
>   }
>   
> +int virtio_pci_add_shm_cap(VirtIOPCIProxy *proxy,
> +                           uint8_t bar, uint64_t offset, uint64_t length,
> +                           uint8_t id)
> +{
> +    struct virtio_pci_cap64 cap = {
> +        .cap.cap_len = sizeof cap,
> +        .cap.cfg_type = VIRTIO_PCI_CAP_SHARED_MEMORY_CFG,
> +    };
> +
> +    cap.cap.bar = bar;
> +    cap.cap.length = cpu_to_le32(length);
> +    cap.length_hi = cpu_to_le32(length >> 32);
> +    cap.cap.offset = cpu_to_le32(offset);
> +    cap.offset_hi = cpu_to_le32(offset >> 32);
> +    cap.cap.id = id;
Why initializing 'cap' using 2 different coding styles?

> +    return virtio_pci_add_mem_cap(proxy, &cap.cap);
> +}