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Subject: Re: [PATCH v2 1/2] KVM: s390: Disallow invalid bits in kvm_valid_regs
 and kvm_dirty_regs
To:     Thomas Huth <thuth@redhat.com>, kvm@vger.kernel.org,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Janosch Frank <frankja@linux.ibm.com>
Cc:     Cornelia Huck <cohuck@redhat.com>, linux-s390@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20190904085200.29021-1-thuth@redhat.com>
 <20190904085200.29021-2-thuth@redhat.com>
 <b34a237f-77a5-2939-624d-0240451f2976@redhat.com>
 <79e5e0a4-78f3-8a61-7311-b711cf4bcd9f@redhat.com>
From:   David Hildenbrand <david@redhat.com>
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Organization: Red Hat GmbH
Message-ID: <27189f65-3c8c-91ed-1f20-5e19ef4e6f38@redhat.com>
Date:   Wed, 4 Sep 2019 11:11:57 +0200
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On 04.09.19 11:10, Thomas Huth wrote:
> On 04/09/2019 11.05, David Hildenbrand wrote:
>> On 04.09.19 10:51, Thomas Huth wrote:
>>> If unknown bits are set in kvm_valid_regs or kvm_dirty_regs, this
>>> clearly indicates that something went wrong in the KVM userspace
>>> application. The x86 variant of KVM already contains a check for
>>> bad bits, so let's do the same on s390x now, too.
>>>
>>> Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
>>> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
>>> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
>>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>>> ---
>>>  arch/s390/include/uapi/asm/kvm.h | 6 ++++++
>>>  arch/s390/kvm/kvm-s390.c         | 4 ++++
>>>  2 files changed, 10 insertions(+)
>>>
>>> diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
>>> index 47104e5b47fd..436ec7636927 100644
>>> --- a/arch/s390/include/uapi/asm/kvm.h
>>> +++ b/arch/s390/include/uapi/asm/kvm.h
>>> @@ -231,6 +231,12 @@ struct kvm_guest_debug_arch {
>>>  #define KVM_SYNC_GSCB   (1UL << 9)
>>>  #define KVM_SYNC_BPBC   (1UL << 10)
>>>  #define KVM_SYNC_ETOKEN (1UL << 11)
>>> +
>>> +#define KVM_SYNC_S390_VALID_FIELDS \
>>> +	(KVM_SYNC_PREFIX | KVM_SYNC_GPRS | KVM_SYNC_ACRS | KVM_SYNC_CRS | \
>>> +	 KVM_SYNC_ARCH0 | KVM_SYNC_PFAULT | KVM_SYNC_VRS | KVM_SYNC_RICCB | \
>>> +	 KVM_SYNC_FPRS | KVM_SYNC_GSCB | KVM_SYNC_BPBC | KVM_SYNC_ETOKEN)
>>> +
>>
>> We didn't care about the S390 for the actual flags, why care now?
> 
> x86 does the same, and we don't want to be worse than x86, do we? ;-)

Yeah, but they do have X86 in every flag - in contrast to us.

> 
> Honestly, this was just one of the differences that I noticed while
> porting the sync_regs_test from x86 to s390x.
> 
>  Thomas
> 


-- 

Thanks,

David / dhildenb