mbox series

[0/2] target/ppc: Fix vextu[bhw][lr]x on big endian hosts

Message ID 20210824201105.2303789-1-matheus.ferst@eldorado.org.br (mailing list archive)
Headers show
Series target/ppc: Fix vextu[bhw][lr]x on big endian hosts | expand

Message

Matheus K. Ferst Aug. 24, 2021, 8:11 p.m. UTC
From: Matheus Ferst <matheus.ferst@eldorado.org.br>

The definition of struct Int128 is currently independent of the host
endianness, causing different results when using the member s128 of
union ppc_vsr_t in big-endian builds with CONFIG_INT128 or
!CONFIG_INT128.

The only PPC instructions that seem to be affected by this issue are the
"Vector Extract Unsigned Byte/Halfword/Word to GPR using GPR-specified
Left/Right-Index." Even on builds with Int128 support, however, their
helpers give the wrong result on big-endian hosts.

The first patch in this series changes the definition of struct Int128
to allow its use in the ppc_vsr_t union. The second patch fixes the
helper definition.

Matheus Ferst (2):
  include/qemu/int128.h: define struct Int128 according to the host
    endianness
  target/ppc: fix vextu[bhw][lr]x helpers

 include/qemu/int128.h   | 19 ++++++++++++-------
 target/ppc/int_helper.c | 38 ++++++++++----------------------------
 2 files changed, 22 insertions(+), 35 deletions(-)

Comments

David Gibson Aug. 25, 2021, 3:02 a.m. UTC | #1
On Tue, Aug 24, 2021 at 05:11:03PM -0300, matheus.ferst@eldorado.org.br wrote:
> From: Matheus Ferst <matheus.ferst@eldorado.org.br>
> 
> The definition of struct Int128 is currently independent of the host
> endianness, causing different results when using the member s128 of
> union ppc_vsr_t in big-endian builds with CONFIG_INT128 or
> !CONFIG_INT128.
> 
> The only PPC instructions that seem to be affected by this issue are the
> "Vector Extract Unsigned Byte/Halfword/Word to GPR using GPR-specified
> Left/Right-Index." Even on builds with Int128 support, however, their
> helpers give the wrong result on big-endian hosts.
> 
> The first patch in this series changes the definition of struct Int128
> to allow its use in the ppc_vsr_t union. The second patch fixes the
> helper definition.

CCing Richard Henderson, who's probably the best qualified to review
these.
Philippe Mathieu-Daudé Aug. 25, 2021, 5:32 a.m. UTC | #2
On 8/24/21 10:11 PM, matheus.ferst@eldorado.org.br wrote:
> From: Matheus Ferst <matheus.ferst@eldorado.org.br>
> 
> The definition of struct Int128 is currently independent of the host
> endianness, causing different results when using the member s128 of
> union ppc_vsr_t in big-endian builds with CONFIG_INT128 or
> !CONFIG_INT128.
> 
> The only PPC instructions that seem to be affected by this issue are the
> "Vector Extract Unsigned Byte/Halfword/Word to GPR using GPR-specified
> Left/Right-Index." Even on builds with Int128 support, however, their
> helpers give the wrong result on big-endian hosts.
> 
> The first patch in this series changes the definition of struct Int128
> to allow its use in the ppc_vsr_t union. The second patch fixes the
> helper definition.
> 
> Matheus Ferst (2):
>   include/qemu/int128.h: define struct Int128 according to the host
>     endianness
>   target/ppc: fix vextu[bhw][lr]x helpers
> 
>  include/qemu/int128.h   | 19 ++++++++++++-------
>  target/ppc/int_helper.c | 38 ++++++++++----------------------------
>  2 files changed, 22 insertions(+), 35 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Mark Cave-Ayland Aug. 25, 2021, 12:55 p.m. UTC | #3
On 24/08/2021 21:11, matheus.ferst@eldorado.org.br wrote:

> From: Matheus Ferst <matheus.ferst@eldorado.org.br>
> 
> The definition of struct Int128 is currently independent of the host
> endianness, causing different results when using the member s128 of
> union ppc_vsr_t in big-endian builds with CONFIG_INT128 or
> !CONFIG_INT128.
> 
> The only PPC instructions that seem to be affected by this issue are the
> "Vector Extract Unsigned Byte/Halfword/Word to GPR using GPR-specified
> Left/Right-Index." Even on builds with Int128 support, however, their
> helpers give the wrong result on big-endian hosts.
> 
> The first patch in this series changes the definition of struct Int128
> to allow its use in the ppc_vsr_t union. The second patch fixes the
> helper definition.
> 
> Matheus Ferst (2):
>    include/qemu/int128.h: define struct Int128 according to the host
>      endianness
>    target/ppc: fix vextu[bhw][lr]x helpers
> 
>   include/qemu/int128.h   | 19 ++++++++++++-------
>   target/ppc/int_helper.c | 38 ++++++++++----------------------------
>   2 files changed, 22 insertions(+), 35 deletions(-)

Hi Matheus,

Slightly unrelated to this patchset, however I see you've managed to make some good 
efforts in consolidating the functionality between big-endian and little-endian host 
systems.

When I first worked on adding host vector support for PPC I noticed there were some 
further places in target/ppc/int_helper.c that could be improved from accessing 
ppc_avr_t fields such as u64 directly and instead using the relevant Vsr*() macros.

If you feel suitably motivated, it would be amazing to see more patches to help this 
further along: basically look in target/ppc/int_helper.c for individual elements such 
as u64 (and also the VECTOR_FOR_INORDER_I macro) and determine which ones are better 
replaced by the relevant Vsr*() macro.


ATB,

Mark.
Matheus K. Ferst Aug. 26, 2021, 1:28 a.m. UTC | #4
On 25/08/2021 09:55, Mark Cave-Ayland wrote:
> [E-MAIL EXTERNO] Não clique em links ou abra anexos, a menos que você 
> possa confirmar o remetente e saber que o conteúdo é seguro. Em caso de 
> e-mail suspeito entre imediatamente em contato com o DTI.
> 
> On 24/08/2021 21:11, matheus.ferst@eldorado.org.br wrote:
> 
>> From: Matheus Ferst <matheus.ferst@eldorado.org.br>
>>
>> The definition of struct Int128 is currently independent of the host
>> endianness, causing different results when using the member s128 of
>> union ppc_vsr_t in big-endian builds with CONFIG_INT128 or
>> !CONFIG_INT128.
>>
>> The only PPC instructions that seem to be affected by this issue are the
>> "Vector Extract Unsigned Byte/Halfword/Word to GPR using GPR-specified
>> Left/Right-Index." Even on builds with Int128 support, however, their
>> helpers give the wrong result on big-endian hosts.
>>
>> The first patch in this series changes the definition of struct Int128
>> to allow its use in the ppc_vsr_t union. The second patch fixes the
>> helper definition.
>>
>> Matheus Ferst (2):
>>    include/qemu/int128.h: define struct Int128 according to the host
>>      endianness
>>    target/ppc: fix vextu[bhw][lr]x helpers
>>
>>   include/qemu/int128.h   | 19 ++++++++++++-------
>>   target/ppc/int_helper.c | 38 ++++++++++----------------------------
>>   2 files changed, 22 insertions(+), 35 deletions(-)
> 
> Hi Matheus,
> 
> Slightly unrelated to this patchset, however I see you've managed to 
> make some good
> efforts in consolidating the functionality between big-endian and 
> little-endian host
> systems.
> 
> When I first worked on adding host vector support for PPC I noticed 
> there were some
> further places in target/ppc/int_helper.c that could be improved from 
> accessing
> ppc_avr_t fields such as u64 directly and instead using the relevant 
> Vsr*() macros.
> 
> If you feel suitably motivated, it would be amazing to see more patches 
> to help this
> further along: basically look in target/ppc/int_helper.c for individual 
> elements such
> as u64 (and also the VECTOR_FOR_INORDER_I macro) and determine which 
> ones are better
> replaced by the relevant Vsr*() macro.
> 
> 
> ATB,
> 
> Mark.

Hi Mark,

That would be a nice change. Our efforts are currently on PowerISA v3.1 
instructions, but I'll try to change that in helpers of things we move 
to decodetree. After completing the new instructions, I can give a shot 
in a Vsr*() patchset.