linux-kernel - Re: [PATCH v6 1/4] kvm: arm64: introduce new flag for non-cacheable IO memory

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Date: Fri, 9 Feb 2024 14:10:51 +0000
From: Ankit Agrawal <ankita@...dia.com>
To: Oliver Upton <oliver.upton@...ux.dev>, Catalin Marinas
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Subject: Re: [PATCH v6 1/4] kvm: arm64: introduce new flag for non-cacheable
 IO memory

>> +	default:
>> +		WARN_ON_ONCE(1);
>
> Return -EINVAL?

Sure.

>> > +   case KVM_PGTABLE_PROT_NORMAL_NC:
>> > +           attr = KVM_S2_MEMATTR(pgt, NORMAL_NC);
>> > +           break;
>>
>> Does it make sense to allow executable here as well? I don't think it's
>> harmful but not sure there's a use-case for it either.
>
> Ah, we should just return EINVAL for that too.
>
> I get that the memory attribute itself is not problematic, but since
> we're only using this thing for MMIO it'd be a rather massive
> bug in KVM... We reject attempts to do this earlier in user_mem_abort().

Ack, will change to test executable and return -EINVAL in that case.