[PATCH 2/2] arm64: cpufeatures: Only check for NV1 if NV is present

[Marek Szyprowski]

Hi

On 12.02.2024 15:47, Marc Zyngier wrote:
> We handle ID_AA64MMFR4_EL1.E2H0 being 0 as NV1 being present.
> However, this is only true if FEAT_NV is implemented.
>
> Add the required check to has_nv1(), avoiding spuriously advertising
> NV1 on HW that doesn't have NV at all.
>
> Fixes: da9af5071b25 ("arm64: cpufeature: Detect HCR_EL2.NV1 being RES0")
> Signed-off-by: Marc Zyngier <maz at kernel.org>

This patch in turn introduces the following warning during boot 
(observed on today's linux-next):

CPU: All CPU(s) started at EL2
CPU features: detected: 32-bit EL0 Support
CPU features: detected: 32-bit EL1 Support
CPU features: detected: CRC32 instructions
------------[ cut here ]------------
WARNING: CPU: 0 PID: 1 at arch/arm64/kernel/cpufeature.c:3369 
this_cpu_has_cap+0x18/0x70
Modules linked in:
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.8.0-rc4-next-20240213 #8014
Hardware name: Khadas VIM3 (DT)
pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : this_cpu_has_cap+0x18/0x70
lr : has_nv1+0x24/0xcc
...
Call trace:
  this_cpu_has_cap+0x18/0x70
  update_cpu_capabilities+0x50/0x134
  setup_system_features+0x30/0x120
  smp_cpus_done+0x48/0xb4
  smp_init+0x7c/0x8c
  kernel_init_freeable+0x18c/0x4e4
  kernel_init+0x20/0x1d8
  ret_from_fork+0x10/0x20
irq event stamp: 2846
hardirqs last  enabled at (2845): [<ffff80008012cf5c>] 
console_unlock+0x164/0x190
hardirqs last disabled at (2846): [<ffff80008123a078>] el1_dbg+0x24/0x8c
softirqs last  enabled at (2842): [<ffff800080010a60>] 
__do_softirq+0x4a0/0x4e8
softirqs last disabled at (2827): [<ffff8000800169b0>] 
____do_softirq+0x10/0x1c
---[ end trace 0000000000000000 ]---
alternatives: applying system-wide alternatives


> ---
>   arch/arm64/kernel/cpufeature.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 2f8958f27e9e..3421b684d340 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1812,8 +1812,9 @@ static bool has_nv1(const struct arm64_cpu_capabilities *entry, int scope)
>   		{}
>   	};
>   
> -	return !(has_cpuid_feature(entry, scope) ||
> -		 is_midr_in_range_list(read_cpuid_id(), nv1_ni_list));
> +	return (this_cpu_has_cap(ARM64_HAS_NESTED_VIRT) &&
> +		!(has_cpuid_feature(entry, scope) ||
> +		  is_midr_in_range_list(read_cpuid_id(), nv1_ni_list)));
>   }
>   
>   #if defined(ID_AA64MMFR0_EL1_TGRAN_LPA2) && defined(ID_AA64MMFR0_EL1_TGRAN_2_SUPPORTED_LPA2)

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland