target/arm: set the correct TI bits for WFIT traps

[PATCH] target/arm: set the correct TI bits for WFIT traps

Posted by Alex Bennée 1 month, 2 weeks ago

The WFIT trap should be reported as 0b10.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 target/arm/tcg/op_helper.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/arm/tcg/op_helper.c b/target/arm/tcg/op_helper.c
index 4d708635068..aa14f15eb62 100644
--- a/target/arm/tcg/op_helper.c
+++ b/target/arm/tcg/op_helper.c
@@ -448,7 +448,7 @@ void HELPER(wfit)(CPUARMState *env, uint64_t timeout)
 
     if (target_el) {
         env->pc -= 4;
-        raise_exception(env, excp, syn_wfx(1, 0xe, 0, false), target_el);
+        raise_exception(env, excp, syn_wfx(1, 0xe, 2, false), target_el);
     }
 
     if (uadd64_overflow(timeout, offset, &nexttick)) {
-- 
2.47.3

Re: [PATCH] target/arm: set the correct TI bits for WFIT traps

Posted by Peter Maydell 1 month, 2 weeks ago

On Fri, 20 Feb 2026 at 17:19, Alex Bennée <alex.bennee@linaro.org> wrote:
>
> The WFIT trap should be reported as 0b10.
>
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> ---
>  target/arm/tcg/op_helper.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/target/arm/tcg/op_helper.c b/target/arm/tcg/op_helper.c
> index 4d708635068..aa14f15eb62 100644
> --- a/target/arm/tcg/op_helper.c
> +++ b/target/arm/tcg/op_helper.c
> @@ -448,7 +448,7 @@ void HELPER(wfit)(CPUARMState *env, uint64_t timeout)
>
>      if (target_el) {
>          env->pc -= 4;
> -        raise_exception(env, excp, syn_wfx(1, 0xe, 0, false), target_el);
> +        raise_exception(env, excp, syn_wfx(1, 0xe, 2, false), target_el);
>      }

It would be nice to also report the register number in the
syndrome (especially since KVM will use it if it's there),
but that is architecturally optional, and getting the TI bits
right is a bug fix.



Applied to target-arm.next, thanks.

-- PMM

Re: [PATCH] target/arm: set the correct TI bits for WFIT traps

Posted by Alex Bennée 1 month, 2 weeks ago

Peter Maydell <peter.maydell@linaro.org> writes:

> On Fri, 20 Feb 2026 at 17:19, Alex Bennée <alex.bennee@linaro.org> wrote:
>>
>> The WFIT trap should be reported as 0b10.
>>
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> ---
>>  target/arm/tcg/op_helper.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/target/arm/tcg/op_helper.c b/target/arm/tcg/op_helper.c
>> index 4d708635068..aa14f15eb62 100644
>> --- a/target/arm/tcg/op_helper.c
>> +++ b/target/arm/tcg/op_helper.c
>> @@ -448,7 +448,7 @@ void HELPER(wfit)(CPUARMState *env, uint64_t timeout)
>>
>>      if (target_el) {
>>          env->pc -= 4;
>> -        raise_exception(env, excp, syn_wfx(1, 0xe, 0, false), target_el);
>> +        raise_exception(env, excp, syn_wfx(1, 0xe, 2, false), target_el);
>>      }
>
> It would be nice to also report the register number in the
> syndrome (especially since KVM will use it if it's there),
> but that is architecturally optional, and getting the TI bits
> right is a bug fix.

Turned out just getting the rd information is trivially simple so I sent
a follow-up series.

  https://patchew.org/QEMU/20260224154347.344219-1-alex.bennee@linaro.org/

>
>
>
> Applied to target-arm.next, thanks.
>
> -- PMM

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro

Re: [PATCH] target/arm: set the correct TI bits for WFIT traps

Posted by Gustavo Romero 1 month, 2 weeks ago

Hi Alex,

On 2/20/26 14:19, Alex Bennée wrote:
> The WFIT trap should be reported as 0b10.
> 
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> ---
>   target/arm/tcg/op_helper.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/target/arm/tcg/op_helper.c b/target/arm/tcg/op_helper.c
> index 4d708635068..aa14f15eb62 100644
> --- a/target/arm/tcg/op_helper.c
> +++ b/target/arm/tcg/op_helper.c
> @@ -448,7 +448,7 @@ void HELPER(wfit)(CPUARMState *env, uint64_t timeout)
>   
>       if (target_el) {
>           env->pc -= 4;
> -        raise_exception(env, excp, syn_wfx(1, 0xe, 0, false), target_el);
> +        raise_exception(env, excp, syn_wfx(1, 0xe, 2, false), target_el);

As per the AArch64.WFxTrap() Arm Arm pseudo code:

Reviewed-by: Gustavo Romero <gustavo.romero@linaro.org>


Cheers,
Gustavo

>       }
>   
>       if (uadd64_overflow(timeout, offset, &nexttick)) {