Re: [Qemu-devel] [PATCH] virtio-pci: implement cfg capability

[Paolo Bonzini <pbonzini@redhat.com>]

On 02/07/2015 15:00, Michael S. Tsirkin wrote:
> +        cfg = (void *)(proxy->pci_dev.config + proxy->config_cap);
> +        off = le32_to_cpu(cfg->cap.offset);
> +        len = le32_to_cpu(cfg->cap.length);
> +
> +        if ((len == 1 || len == 2 || len == 4)) {
> +            address_space_write(&proxy->modern_as, off,
> +                                MEMTXATTRS_UNSPECIFIED,
> +                                cfg->pci_cfg_data, len);
> +        }

This parses pci_cfg_data in target endianness I think.  You just want to
move the little-endian value from the config cap to the little-endian
value in the modern_as, so you need to use ldl_le_p and
address_space_stl_le.

> +    }
> +}
> +
> +static uint32_t virtio_read_config(PCIDevice *pci_dev,
> +                                   uint32_t address, int len)
> +{
> +    VirtIOPCIProxy *proxy = DO_UPCAST(VirtIOPCIProxy, pci_dev, pci_dev);
> +    struct virtio_pci_cfg_cap *cfg;
> +
> +    if (proxy->config_cap &&
> +        ranges_overlap(address, len, proxy->config_cap + offsetof(struct virtio_pci_cfg_cap,
> +                                                                  pci_cfg_data),
> +                       sizeof cfg->pci_cfg_data)) {
> +        uint32_t off;
> +        uint32_t len;
> +
> +        cfg = (void *)(proxy->pci_dev.config + proxy->config_cap);
> +        off = le32_to_cpu(cfg->cap.offset);
> +        len = le32_to_cpu(cfg->cap.length);
> +
> +        if ((len == 1 || len == 2 || len == 4)) {
> +            address_space_read(&proxy->modern_as, off,
> +                                MEMTXATTRS_UNSPECIFIED,
> +                                cfg->pci_cfg_data, len);

Same here, use address_space_ldl_le to read into an int, and stl_le_p to
write into cfg->pci_cfg_data.

The best way to check it, of course, is to write a unit test! :)  But
you could also use a Linux BE guest on LE host.

Everything else looks good.

Paolo