linux-kernel - Re: [PATCH] selftests: kvm: Check whether SIDA memop fails for normal guests

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Message-ID: <c01824a7-9d15-1356-2530-04c6112ace65@redhat.com>
Date:   Tue, 15 Feb 2022 10:59:25 +0100
From:   Thomas Huth <thuth@...hat.com>
To:     Janis Schoetterl-Glausch <scgl@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>, kvm@...r.kernel.org
Cc:     David Hildenbrand <david@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests: kvm: Check whether SIDA memop fails for normal
 guests

On 15/02/2022 10.54, Janis Schoetterl-Glausch wrote:
> On 2/15/22 08:48, Thomas Huth wrote:
>> Commit 2c212e1baedc ("KVM: s390: Return error on SIDA memop on normal
>> guest") fixed the behavior of the SIDA memops for normal guests. It
>> would be nice to have a way to test whether the current kernel has
>> the fix applied or not. Thus add a check to the KVM selftests for
>> these two memops.
>>
>> Signed-off-by: Thomas Huth <thuth@...hat.com>
>> ---
>>   tools/testing/selftests/kvm/s390x/memop.c | 15 +++++++++++++++
>>   1 file changed, 15 insertions(+)
>>
>> diff --git a/tools/testing/selftests/kvm/s390x/memop.c b/tools/testing/selftests/kvm/s390x/memop.c
>> index 9f49ead380ab..d19c3ffdea3f 100644
>> --- a/tools/testing/selftests/kvm/s390x/memop.c
>> +++ b/tools/testing/selftests/kvm/s390x/memop.c
>> @@ -160,6 +160,21 @@ int main(int argc, char *argv[])
>>   	run->psw_mask &= ~(3UL << (63 - 17));   /* Disable AR mode */
>>   	vcpu_run(vm, VCPU_ID);                  /* Run to sync new state */
>>
>> +	/* Check that the SIDA calls are rejected for non-protected guests */
>> +	ksmo.gaddr = 0;
>> +	ksmo.flags = 0;
>> +	ksmo.size = 8;
>> +	ksmo.op = KVM_S390_MEMOP_SIDA_READ;
>> +	ksmo.buf = (uintptr_t)mem1;
>> +	ksmo.sida_offset = 0x1c0;
> 
> What is the rational for that constant?
> Any would do, as long as size + offset < PAGE_SIZE, correct?

Right, it's rather a random value.

  Thomas