Re: [Qemu-devel] [PATCH± SVM I/O permission bitmap for user-level (ring-3) code ignored

[Alexander Boettcher]

On 09.03.2017 13:42, Paolo Bonzini wrote:
> On 05/03/2017 19:21, Alexander Boettcher wrote:
>> the SVM I/O permission bitmap for user-level (ring-3) VM code running in
>> SVM seems to be ignored and causes a GP-fault. (Actual the IO permission
>> was granted by the kernel via the TSS I/O port permission bitmap).
>>
>> After some debugging the GP code originates from target/i386/translate.c
>> gen_check_io() within the if(s->pe && (s->cpl > s->iopl || s->vm86))
>> condition. However, the actual SVM IO permission bitmap is checked after
>> that condition, which succeeds and would permit the access.


> The code as is
> written now matches the AMD manual: "Exceptions related to virtual x86
> mode, IOPL, or the TSS-bitmap are checked before the SVM intercept
> check. All other exceptions are checked after the SVM intercept check".

I see. I will re-check, maybe we're doing things wrong in the VMM.

Thanks.
-- 
Alexander Boettcher
Genode Labs

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