Force ThumbEE support to not available in the version of the PFR0
register value we present to guest.
Xen does not support ThumbEE and will trap all access to ThumbEE
registers so do not report it being supported if the hardware supports
it.

Fixes: 5bbe1fe413f9 ("ARM: Drop ThumbEE support")
Signed-off-by: Bertrand Marquis <bertrand.marquis@arm.com>
---
 xen/arch/arm/cpufeature.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/xen/arch/arm/cpufeature.c b/xen/arch/arm/cpufeature.c
index 1a80738571e3..4cde208e721a 100644
--- a/xen/arch/arm/cpufeature.c
+++ b/xen/arch/arm/cpufeature.c
@@ -225,6 +225,7 @@ static int __init create_domain_cpuinfo(void)
 #ifdef CONFIG_ARM_64
     domain_cpuinfo.pfr64.amu = 0;
 #endif
+    domain_cpuinfo.pfr32.thumbee = 0;
     domain_cpuinfo.pfr32.amu = 0;
 
     /* Hide RAS support as Xen does not support it */
-- 
2.51.2

Hi Bertrand,

> On 9 Dec 2025, at 10:37, Bertrand Marquis <Bertrand.Marquis@arm.com> wrote:
> 
> Force ThumbEE support to not available in the version of the PFR0
> register value we present to guest.
> Xen does not support ThumbEE and will trap all access to ThumbEE
> registers so do not report it being supported if the hardware supports
> it.
> 
> Fixes: 5bbe1fe413f9 ("ARM: Drop ThumbEE support")
> Signed-off-by: Bertrand Marquis <bertrand.marquis@arm.com>
> ---
> xen/arch/arm/cpufeature.c | 1 +
> 1 file changed, 1 insertion(+)
> 
> diff --git a/xen/arch/arm/cpufeature.c b/xen/arch/arm/cpufeature.c
> index 1a80738571e3..4cde208e721a 100644
> --- a/xen/arch/arm/cpufeature.c
> +++ b/xen/arch/arm/cpufeature.c
> @@ -225,6 +225,7 @@ static int __init create_domain_cpuinfo(void)
> #ifdef CONFIG_ARM_64
>     domain_cpuinfo.pfr64.amu = 0;
> #endif
> +    domain_cpuinfo.pfr32.thumbee = 0;
>     domain_cpuinfo.pfr32.amu = 0;
> 
>     /* Hide RAS support as Xen does not support it */
> -- 
> 2.51.2
> 
> 

This solves the issue I observed.

Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
Tested-by: Luca Fancellu <luca.fancellu@arm.com>

Cheers,
Luca

On 09/12/2025 11:37, Bertrand Marquis wrote:
> Force ThumbEE support to not available in the version of the PFR0
> register value we present to guest.
> Xen does not support ThumbEE and will trap all access to ThumbEE
> registers so do not report it being supported if the hardware supports
> it.
> 
> Fixes: 5bbe1fe413f9 ("ARM: Drop ThumbEE support")
> Signed-off-by: Bertrand Marquis <bertrand.marquis@arm.com>
> ---
>  xen/arch/arm/cpufeature.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/xen/arch/arm/cpufeature.c b/xen/arch/arm/cpufeature.c
> index 1a80738571e3..4cde208e721a 100644
> --- a/xen/arch/arm/cpufeature.c
> +++ b/xen/arch/arm/cpufeature.c
> @@ -225,6 +225,7 @@ static int __init create_domain_cpuinfo(void)
>  #ifdef CONFIG_ARM_64
>      domain_cpuinfo.pfr64.amu = 0;
>  #endif
> +    domain_cpuinfo.pfr32.thumbee = 0;
Let's not split AMU section. Also, it looks like a convention here to add a
comment about feature we disabled. With:

    /* Hide ThumbEE support */
    domain_cpuinfo.pfr32.thumbee = 0;

Reviewed-by: Michal Orzel <michal.orzel@amd.com>

that could be done on commit.

Do you have a pipeline link?

~Michal

>      domain_cpuinfo.pfr32.amu = 0;
>  
>      /* Hide RAS support as Xen does not support it */

Hi Michal,

> On 9 Dec 2025, at 10:42, Orzel, Michal <Michal.Orzel@amd.com> wrote:
> 
> 
> 
> On 09/12/2025 11:37, Bertrand Marquis wrote:
>> Force ThumbEE support to not available in the version of the PFR0
>> register value we present to guest.
>> Xen does not support ThumbEE and will trap all access to ThumbEE
>> registers so do not report it being supported if the hardware supports
>> it.
>> 
>> Fixes: 5bbe1fe413f9 ("ARM: Drop ThumbEE support")
>> Signed-off-by: Bertrand Marquis <bertrand.marquis@arm.com>
>> ---
>> xen/arch/arm/cpufeature.c | 1 +
>> 1 file changed, 1 insertion(+)
>> 
>> diff --git a/xen/arch/arm/cpufeature.c b/xen/arch/arm/cpufeature.c
>> index 1a80738571e3..4cde208e721a 100644
>> --- a/xen/arch/arm/cpufeature.c
>> +++ b/xen/arch/arm/cpufeature.c
>> @@ -225,6 +225,7 @@ static int __init create_domain_cpuinfo(void)
>> #ifdef CONFIG_ARM_64
>>     domain_cpuinfo.pfr64.amu = 0;
>> #endif
>> +    domain_cpuinfo.pfr32.thumbee = 0;
> Let's not split AMU section. Also, it looks like a convention here to add a
> comment about feature we disabled. With:
> 
>    /* Hide ThumbEE support */
>    domain_cpuinfo.pfr32.thumbee = 0;
> 
> Reviewed-by: Michal Orzel <michal.orzel@amd.com>
> 

Ack, happy if you fix that on commit.

> that could be done on commit.
> 
> Do you have a pipeline link?

https://gitlab.com/xen-project/people/bmarquis/xen-ffa-research/-/pipelines/2204086293

Cheers
Bertrand