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

[Stefan Weil <sw@weilnetz.de>]

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Am 02.01.2016 um 09:02 schrieb Cao jin:
> 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.
>
>  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);

The type cast is not needed here, because read accepts any pointer
type for the buffer argument.

While looking at that code, I noticed more potential issues:

* The open statement needs O_RDWR | O_BINARY, otherwise the code won't
work on Windows.

* The len argument can obviously be 2 or 4. Will endianness handling
work for both cases?

Regards,
Stefan



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