[Qemu-devel] [PATCH] vmxnet: Don't use bswap_64 for constants

[Qemu-devel] [PATCH] vmxnet: Don't use bswap_64 for constants

[Richard Henderson]

This macro is used in the context of defining enum values.
We can't use a function call in that case.

Cc: qemu-trivial@nongnu.org
Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 hw/vmxnet3.h | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/hw/vmxnet3.h b/hw/vmxnet3.h
index 7db0c8f..cd9ac85 100644
--- a/hw/vmxnet3.h
+++ b/hw/vmxnet3.h
@@ -37,7 +37,15 @@
 #define __packed QEMU_PACKED
 
 #if defined(HOST_WORDS_BIGENDIAN)
-#define const_cpu_to_le64(x) bswap_64(x)
+#define const_cpu_to_le64(x) \
+        (((x & 0x00000000000000ffULL) << 56) | \
+         ((x & 0x000000000000ff00ULL) << 40) | \
+         ((x & 0x0000000000ff0000ULL) << 24) | \
+         ((x & 0x00000000ff000000ULL) <<  8) | \
+         ((x & 0x000000ff00000000ULL) >>  8) | \
+         ((x & 0x0000ff0000000000ULL) >> 24) | \
+         ((x & 0x00ff000000000000ULL) >> 40) | \
+         ((x & 0xff00000000000000ULL) >> 56))
 #define __BIG_ENDIAN_BITFIELD
 #else
 #define const_cpu_to_le64(x) (x)
-- 
1.8.1.4

Re: [Qemu-devel] [PATCH] vmxnet: Don't use bswap_64 for constants

[Andreas Färber]

Am 27.03.2013 19:47, schrieb Richard Henderson:
> This macro is used in the context of defining enum values.
> We can't use a function call in that case.
> 
> Cc: qemu-trivial@nongnu.org
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
>  hw/vmxnet3.h | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/vmxnet3.h b/hw/vmxnet3.h
> index 7db0c8f..cd9ac85 100644
> --- a/hw/vmxnet3.h
> +++ b/hw/vmxnet3.h
> @@ -37,7 +37,15 @@
>  #define __packed QEMU_PACKED
>  
>  #if defined(HOST_WORDS_BIGENDIAN)
> -#define const_cpu_to_le64(x) bswap_64(x)
> +#define const_cpu_to_le64(x) \
> +        (((x & 0x00000000000000ffULL) << 56) | \
> +         ((x & 0x000000000000ff00ULL) << 40) | \
> +         ((x & 0x0000000000ff0000ULL) << 24) | \
> +         ((x & 0x00000000ff000000ULL) <<  8) | \
> +         ((x & 0x000000ff00000000ULL) >>  8) | \
> +         ((x & 0x0000ff0000000000ULL) >> 24) | \
> +         ((x & 0x00ff000000000000ULL) >> 40) | \
> +         ((x & 0xff00000000000000ULL) >> 56))

Being a macro, shouldn't this better use (x) for operator precedence?

Andreas

>  #define __BIG_ENDIAN_BITFIELD
>  #else
>  #define const_cpu_to_le64(x) (x)
> 


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GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg

Re: [Qemu-devel] [PATCH] vmxnet: Don't use bswap_64 for constants

[Richard Henderson]

On 2013-03-27 16:42, Andreas Färber wrote:
> Am 27.03.2013 19:47, schrieb Richard Henderson:
>> This macro is used in the context of defining enum values.
>> We can't use a function call in that case.
>>
>> Cc: qemu-trivial@nongnu.org
>> Signed-off-by: Richard Henderson <rth@twiddle.net>
>> ---
>>   hw/vmxnet3.h | 10 +++++++++-
>>   1 file changed, 9 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/vmxnet3.h b/hw/vmxnet3.h
>> index 7db0c8f..cd9ac85 100644
>> --- a/hw/vmxnet3.h
>> +++ b/hw/vmxnet3.h
>> @@ -37,7 +37,15 @@
>>   #define __packed QEMU_PACKED
>>
>>   #if defined(HOST_WORDS_BIGENDIAN)
>> -#define const_cpu_to_le64(x) bswap_64(x)
>> +#define const_cpu_to_le64(x) \
>> +        (((x & 0x00000000000000ffULL) << 56) | \
>> +         ((x & 0x000000000000ff00ULL) << 40) | \
>> +         ((x & 0x0000000000ff0000ULL) << 24) | \
>> +         ((x & 0x00000000ff000000ULL) <<  8) | \
>> +         ((x & 0x000000ff00000000ULL) >>  8) | \
>> +         ((x & 0x0000ff0000000000ULL) >> 24) | \
>> +         ((x & 0x00ff000000000000ULL) >> 40) | \
>> +         ((x & 0xff00000000000000ULL) >> 56))
>
> Being a macro, shouldn't this better use (x) for operator precedence?

It doesn't matter for this usage.

Nor, according to other threads that appeared on the list today, is this
the right fix, since the bswap itself turns out to be bogus.

Myself, I never tested the driver code, just fixed the compile error.


r~

Re: [Qemu-devel] [Qemu-trivial] [PATCH] vmxnet: Don't use bswap_64 for constants

[Stefan Hajnoczi]

On Wed, Mar 27, 2013 at 05:52:56PM -0700, Richard Henderson wrote:
> On 2013-03-27 16:42, Andreas Färber wrote:
> >Am 27.03.2013 19:47, schrieb Richard Henderson:
> >>This macro is used in the context of defining enum values.
> >>We can't use a function call in that case.
> >>
> >>Cc: qemu-trivial@nongnu.org
> >>Signed-off-by: Richard Henderson <rth@twiddle.net>
> >>---
> >>  hw/vmxnet3.h | 10 +++++++++-
> >>  1 file changed, 9 insertions(+), 1 deletion(-)
> >>
> >>diff --git a/hw/vmxnet3.h b/hw/vmxnet3.h
> >>index 7db0c8f..cd9ac85 100644
> >>--- a/hw/vmxnet3.h
> >>+++ b/hw/vmxnet3.h
> >>@@ -37,7 +37,15 @@
> >>  #define __packed QEMU_PACKED
> >>
> >>  #if defined(HOST_WORDS_BIGENDIAN)
> >>-#define const_cpu_to_le64(x) bswap_64(x)
> >>+#define const_cpu_to_le64(x) \
> >>+        (((x & 0x00000000000000ffULL) << 56) | \
> >>+         ((x & 0x000000000000ff00ULL) << 40) | \
> >>+         ((x & 0x0000000000ff0000ULL) << 24) | \
> >>+         ((x & 0x00000000ff000000ULL) <<  8) | \
> >>+         ((x & 0x000000ff00000000ULL) >>  8) | \
> >>+         ((x & 0x0000ff0000000000ULL) >> 24) | \
> >>+         ((x & 0x00ff000000000000ULL) >> 40) | \
> >>+         ((x & 0xff00000000000000ULL) >> 56))
> >
> >Being a macro, shouldn't this better use (x) for operator precedence?
> 
> It doesn't matter for this usage.
> 
> Nor, according to other threads that appeared on the list today, is this
> the right fix, since the bswap itself turns out to be bogus.

Dmitry said he's sending a fix, will wait for that.

Stefan