Re: [Qemu-devel] [PATCH v3] bugfix: passing reference instead of value

["Michael S. Tsirkin" <mst@redhat.com>]

On Sat, Jan 02, 2016 at 04:02:20PM +0800, Cao jin wrote:
> Fix the bug introduced by 595a4f07: function host_pci_config_read() should be
> pass-by-reference, not value.
> 
> Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
> ---
> v3 changelog:
> 1. Remove cpu_to_le32() since the code only runs on X86.

It really should be le32_to_cpu and a separate patch,
but I think it's preferable to have it there
since people tend to copy code around.

But in any case, before merging any patches in this function I'd like to
hear a response from someone explaining why is this function necessary
at all, since it provably never did anything useful.

> 
>  hw/pci-host/piix.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
> index 715208b..924f0fa 100644
> --- a/hw/pci-host/piix.c
> +++ b/hw/pci-host/piix.c
> @@ -761,7 +761,7 @@ static const IGDHostInfo igd_host_bridge_infos[] = {
>      {0xa8, 4},  /* SNB: base of GTT stolen memory */
>  };
>  
> -static int host_pci_config_read(int pos, int len, uint32_t val)
> +static int host_pci_config_read(int pos, int len, uint32_t *val)
>  {
>      char path[PATH_MAX];
>      int config_fd;
> @@ -784,12 +784,14 @@ static int host_pci_config_read(int pos, int len, uint32_t val)
>          ret = -errno;
>          goto out;
>      }
> +
>      do {
> -        rc = read(config_fd, (uint8_t *)&val, len);
> +        rc = read(config_fd, (uint8_t *)val, len);
>      } while (rc < 0 && (errno == EINTR || errno == EAGAIN));
>      if (rc != len) {
>          ret = -errno;
>      }
> +
>  out:
>      close(config_fd);
>      return ret;
> @@ -805,7 +807,7 @@ static int igd_pt_i440fx_initfn(struct PCIDevice *pci_dev)
>      for (i = 0; i < num; i++) {
>          pos = igd_host_bridge_infos[i].offset;
>          len = igd_host_bridge_infos[i].len;
> -        rc = host_pci_config_read(pos, len, val);
> +        rc = host_pci_config_read(pos, len, &val);
>          if (rc) {
>              return -ENODEV;
>          }
> -- 
> 2.1.0
> 
>