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Subject: Re: [PATCH v2 1/2] KVM: s390: Disallow invalid bits in kvm_valid_regs
 and kvm_dirty_regs
To:     David Hildenbrand <david@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>
From:   Thomas Huth <thuth@redhat.com>
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Organization: Red Hat
Message-ID: <79e5e0a4-78f3-8a61-7311-b711cf4bcd9f@redhat.com>
Date:   Wed, 4 Sep 2019 11:10:45 +0200
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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? ;-)

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

 Thomas