Re: [PATCH v2 4/7] pc-bios/s390-ccw: Add support for virtio-net-pci IPL

["Jason J. Herne" <jjherne@linux.ibm.com>]

On 9/3/26 12:24 PM, Zhuoying Cai wrote:
> Enable network booting via virtio-net-pci by implementing PCI transport
> support for virtio-net.
> 
> This patch also extends endianness handling for virtio PCI ring operations in
> little-endian to ensure correct behavior on s390x.
> 
> Signed-off-by: Zhuoying Cai <zycai@linux.ibm.com>
> ---
>   pc-bios/s390-ccw/main.c       |  1 +
>   pc-bios/s390-ccw/netmain.c    |  9 +++++++-
>   pc-bios/s390-ccw/virtio-net.c | 41 ++++++++++++++++++++++++++++-------
>   pc-bios/s390-ccw/virtio-pci.c | 18 +++++++++++++++
>   4 files changed, 60 insertions(+), 9 deletions(-)
> 
> diff --git a/pc-bios/s390-ccw/main.c b/pc-bios/s390-ccw/main.c
> index 8fc1cbf653..28cab3b411 100644
> --- a/pc-bios/s390-ccw/main.c
> +++ b/pc-bios/s390-ccw/main.c
> @@ -332,6 +332,7 @@ static void ipl_pci_device(void)
>       }
>   
>       switch (vdev->dev_type) {
> +    case VIRTIO_ID_NET:
>       case VIRTIO_ID_BLOCK:
>           if (virtio_setup() == 0) {
>               zipl_load(); /* only return on error */
> diff --git a/pc-bios/s390-ccw/netmain.c b/pc-bios/s390-ccw/netmain.c
> index bcb62bf6ca..e42e049063 100644
> --- a/pc-bios/s390-ccw/netmain.c
> +++ b/pc-bios/s390-ccw/netmain.c
> @@ -498,7 +498,14 @@ int netmain(void)
>       sclp_setup();
>       puts("Network boot starting...");
>   
> -    if (!virtio_ccw_net_setup()) {
> +    /*
> +     * CCW devices require subchannel enumeration here.
> +     * PCI devices don't require specific setup: the transport is already
> +     * initialized by ipl_pci_device(), and virtio_is_supported() is checked
> +     * later in virtio_net_init().
> +     */
> +    if (virtio_get_device()->ipl_type == S390_IPL_TYPE_CCW &&
> +        !virtio_ccw_net_setup()) {
>           puts("No valid virtio ccw net device found.");
>           return -1;
>       }
> diff --git a/pc-bios/s390-ccw/virtio-net.c b/pc-bios/s390-ccw/virtio-net.c
> index afa728bc32..418759565d 100644
> --- a/pc-bios/s390-ccw/virtio-net.c
> +++ b/pc-bios/s390-ccw/virtio-net.c
> @@ -68,7 +68,22 @@ int virtio_net_init(void *mac_addr)
>       rx_last_idx = 0;
>   
>       vdev->guest_features[0] = VIRTIO_NET_F_MAC_BIT;
> -    virtio_ccw_setup(vdev);
> +    switch (virtio_get_device()->ipl_type) {
> +    case S390_IPL_TYPE_CCW:
> +        if (virtio_ccw_setup(vdev)) {
> +            puts("Setup failed for virtio-net-ccw");
> +            return -1;
> +        }
> +        break;
> +    case S390_IPL_TYPE_PCI:
> +        if (virtio_pci_setup(vdev)) {
> +            puts("Setup failed for virtio-net-pci");
> +            return -1;
> +        }
> +        break;
> +    default:
> +        return -1;
> +    }
>   
>       if (!(vdev->guest_features[0] & VIRTIO_NET_F_MAC_BIT)) {
>           puts("virtio-net device does not support the MAC address feature");
> @@ -121,22 +136,30 @@ int recv(int fd, void *buf, int maxlen, int flags)
>       VRing *rxvq = &vdev->vrings[VQ_RX];
>       int len, id;
>       uint8_t *pkt;
> +    uint16_t rx_used_idx, rx_avail_idx;
> +    uint32_t rx_used_len, rx_used_id;
> +    uint64_t rx_desc_addr;
>   
> -    if (rx_last_idx == rxvq->used->idx) {
> +    rx_used_idx = virtio_tswap16(rxvq->used->idx);
> +    if (rx_last_idx == rx_used_idx) {
>           return 0;
>       }
>   
> -    len = rxvq->used->ring[rx_last_idx % rxvq->num].len - virtio_net_hdr_size;
> +    rx_used_len = virtio_tswap32(rxvq->used->ring[rx_last_idx % rxvq->num].len);
> +    rx_used_id = virtio_tswap32(rxvq->used->ring[rx_last_idx % rxvq->num].id);
> +
> +    len = rx_used_len - virtio_net_hdr_size;
>       if (len > maxlen) {
>           puts("virtio-net: Receive buffer too small");
>           len = maxlen;
>       }
> -    id = rxvq->used->ring[rx_last_idx % rxvq->num].id % rxvq->num;
> -    pkt = (uint8_t *)(rxvq->desc[id].addr + virtio_net_hdr_size);
> +    id = rx_used_id % rxvq->num;
> +    rx_desc_addr = virtio_tswap64(rxvq->desc[id].addr);
> +    pkt = (uint8_t *)(rx_desc_addr + virtio_net_hdr_size);
>   
>   #if DEBUG_VIRTIO_NET   /* Dump packet */
>       int i;
> -    printf("\nbuf %p: len=%i\n", (void *)rxvq->desc[id].addr, len);
> +    printf("\nbuf %p: len=%i\n", (void *)rx_desc_addr, len);
>       for (i = 0; i < 64; i++) {
>           printf(" %02x", pkt[i]);
>           if ((i % 16) == 15) {
> @@ -150,8 +173,10 @@ int recv(int fd, void *buf, int maxlen, int flags)
>       memcpy(buf, pkt, len);
>   
>       /* Mark buffer as available to the host again */
> -    rxvq->avail->ring[rxvq->avail->idx % rxvq->num] = id;
> -    rxvq->avail->idx = rxvq->avail->idx + 1;
> +    rx_avail_idx = virtio_tswap16(rxvq->avail->idx);
> +    rxvq->avail->ring[rx_avail_idx % rxvq->num] = virtio_tswap16(id);
> +    rx_avail_idx++;
> +    rxvq->avail->idx = virtio_tswap16(rx_avail_idx);
>       vring_notify(rxvq);
>   
>       /* Move index to next entry */
> diff --git a/pc-bios/s390-ccw/virtio-pci.c b/pc-bios/s390-ccw/virtio-pci.c
> index f501252c81..147a82895f 100644
> --- a/pc-bios/s390-ccw/virtio-pci.c
> +++ b/pc-bios/s390-ccw/virtio-pci.c
> @@ -52,6 +52,10 @@ void virtio_pci_id2type(VDev *vdev, uint16_t device_id)
>       case 0x1001:
>           vdev->dev_type = VIRTIO_ID_BLOCK;
>           break;
> +    case 0x1041:
> +    case 0x1000:
> +        vdev->dev_type = VIRTIO_ID_NET;
> +        break;
>       default:
>           vdev->dev_type = 0;
>       }
> @@ -199,6 +203,14 @@ static int virtio_pci_get_blk_config(void)
>       return rc;
>   }
>   
> +static int virtio_pci_get_net_config(void)
> +{
> +    VirtioNetConfig *cfg = &virtio_get_device()->config.net;
> +    int rc = vpci_read_flex(d_cap.off, d_cap.bar, cfg, sizeof(VirtioNetConfig));
> +
> +    return rc;
> +}
> +

Simplify to this:

static int virtio_pci_get_net_config(void)
{
     VirtioNetConfig *cfg = &virtio_get_device()->config.net;

     return vpci_read_flex(d_cap.off, d_cap.bar, cfg, 
sizeof(VirtioNetConfig));
}


>   static int virtio_pci_negotiate(void)
>   {
>       int i, rc;
> @@ -330,6 +342,7 @@ bool virtio_pci_is_supported(VDev *vdev)
>       if (vdev->vendor_id == PCI_VENDOR_VIRTIO) {
>           switch (vdev->dev_type) {
>           case VIRTIO_ID_BLOCK:
> +        case VIRTIO_ID_NET:
>               return true;
>           default:
>               return false;
> @@ -384,6 +397,11 @@ int virtio_pci_setup(VDev *vdev)
>           vdev->cmd_vr_idx = 0;
>           virtio_pci_get_blk_config();
>           break;
> +    case VIRTIO_ID_NET:
> +        vdev->nr_vqs = 2;
> +        vdev->cmd_vr_idx = 0;

cmd_vr_idx is never actually used for net devices. I'm thinking we want 
to skip setting it here. It's actually already set to 0 above, in common 
code, before we know what device type we're dealing with.