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

[Paolo Bonzini <pbonzini@redhat.com>]

On 02/01/2016 10:06, Stefan Weil wrote:
> 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?

Not sure why this is in pci-host/piix.c, but it's only used on Intel
processors and only on Linux.

Paolo