Re: [Qemu-devel] [PATCH] virtio-pci: replace byte swap hack

[Alexander Graf]

On 30.12.2012, at 13:55, Blue Swirl wrote:

> Remove byte swaps by declaring the config space
> as native endian.

This is wrong. Virtio-pci config space is split into 2 regions. One with native 
endianness, the other one with little endian.


Alex

> 
> Signed-off-by: Blue Swirl <address@hidden>
> ---
> exec.c          |   18 ------------------
> hw/virtio-pci.c |   17 +----------------
> 2 files changed, 1 insertions(+), 34 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index a6923ad..140eb56 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -2587,24 +2587,6 @@ int cpu_memory_rw_debug(CPUArchState *env, 
> target_ulong addr,
> }
> #endif
> 
> -#if !defined(CONFIG_USER_ONLY)
> -
> -/*
> - * A helper function for the _utterly broken_ virtio device model to find 
> out if
> - * it's running on a big endian machine. Don't do this at home kids!
> - */
> -bool virtio_is_big_endian(void);
> -bool virtio_is_big_endian(void)
> -{
> -#if defined(TARGET_WORDS_BIGENDIAN)
> -    return true;
> -#else
> -    return false;
> -#endif
> -}
> -
> -#endif
> -
> #ifndef CONFIG_USER_ONLY
> bool cpu_physical_memory_is_io(hwaddr phys_addr)
> {
> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> index d2d2454..df78a3b 100644
> --- a/hw/virtio-pci.c
> +++ b/hw/virtio-pci.c
> @@ -92,9 +92,6 @@
>  */
> #define wmb() do { } while (0)
> 
> -/* HACK for virtio to determine if it's running a big endian guest */
> -bool virtio_is_big_endian(void);
> -
> /* virtio device */
> 
> static void virtio_pci_notify(void *opaque, uint16_t vector)
> @@ -390,15 +387,9 @@ static uint64_t virtio_pci_config_read(void *opaque, 
> hwaddr addr,
>         break;
>     case 2:
>         val = virtio_config_readw(proxy->vdev, addr);
> -        if (virtio_is_big_endian()) {
> -            val = bswap16(val);
> -        }
>         break;
>     case 4:
>         val = virtio_config_readl(proxy->vdev, addr);
> -        if (virtio_is_big_endian()) {
> -            val = bswap32(val);
> -        }
>         break;
>     }
>     return val;
> @@ -423,15 +414,9 @@ static void virtio_pci_config_write(void *opaque, hwaddr 
> addr,
>         virtio_config_writeb(proxy->vdev, addr, val);
>         break;
>     case 2:
> -        if (virtio_is_big_endian()) {
> -            val = bswap16(val);
> -        }
>         virtio_config_writew(proxy->vdev, addr, val);
>         break;
>     case 4:
> -        if (virtio_is_big_endian()) {
> -            val = bswap32(val);
> -        }
>         virtio_config_writel(proxy->vdev, addr, val);
>         break;
>     }
> @@ -444,7 +429,7 @@ static const MemoryRegionOps virtio_pci_config_ops = {
>         .min_access_size = 1,
>         .max_access_size = 4,
>     },
> -    .endianness = DEVICE_LITTLE_ENDIAN,
> +    .endianness = DEVICE_NATIVE_ENDIAN,
> };
> 
> static void virtio_write_config(PCIDevice *pci_dev, uint32_t address,
> -- 
> 1.7.2.5
> 
>