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Re: [PATCH] xen/arm: Set ThumbEE as not present in PFR0


  • To: Bertrand Marquis <bertrand.marquis@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: "Orzel, Michal" <michal.orzel@xxxxxxx>
  • Date: Tue, 9 Dec 2025 11:42:41 +0100
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  • Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
  • Delivery-date: Tue, 09 Dec 2025 10:42:51 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>


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@xxxxxxx>
> ---
>  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@xxxxxxx>

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 */




 


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