Re: [PATCH] x86/cpufeatures: Force disable X86_FEATURE_ENQCMD and remove update_pasid()

[Thomas Gleixner]

On Wed, Jun 02 2021 at 12:14, Borislav Petkov wrote:

> On Sat, May 29, 2021 at 11:17:30AM +0200, Thomas Gleixner wrote:
>> --- a/arch/x86/include/asm/disabled-features.h
>> +++ b/arch/x86/include/asm/disabled-features.h
>> @@ -56,11 +56,8 @@
>>  # define DISABLE_PTI		(1 << (X86_FEATURE_PTI & 31))
>>  #endif
>>  
>> -#ifdef CONFIG_IOMMU_SUPPORT
>> -# define DISABLE_ENQCMD	0
>> -#else
>> -# define DISABLE_ENQCMD (1 << (X86_FEATURE_ENQCMD & 31))
>> -#endif
>> +/* Force disable because it's broken beyond repair */
>> +#define DISABLE_ENQCMD		(1 << (X86_FEATURE_ENQCMD & 31))
>
> Yeah, for that to work we need:
>
> ---
> From: Borislav Petkov <bp@xxxxxxx>
> Date: Wed, 2 Jun 2021 12:07:52 +0200
> Subject: [PATCH] dmaengine: idxd: Use cpu_feature_enabled()
>
> When testing x86 feature bits, use cpu_feature_enabled() so that
> build-disabled features can remain off, regardless of what CPUID says.
>
> Fixes: 8e50d392652f ("dmaengine: idxd: Add shared workqueue support")
> Signed-off-by: Borislav Petkov <bp@xxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>

Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

Thanks for spotting this!

       tglx