linux-kernel - Re: [PATCH v1 0/9] KVM selftests for s390x

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Message-Id: <f25b27c1-f682-b3f3-1fa8-492a2ef189eb@de.ibm.com>
Date:   Fri, 24 May 2019 14:56:37 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     David Hildenbrand <david@...hat.com>,
        Thomas Huth <thuth@...hat.com>,
        Janosch Frank <frankja@...ux.ibm.com>, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Shuah Khan <shuah@...nel.org>,
        Cornelia Huck <cohuck@...hat.com>,
        Andrew Jones <drjones@...hat.com>,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-s390@...r.kernel.org
Subject: Re: [PATCH v1 0/9] KVM selftests for s390x



On 24.05.19 14:36, David Hildenbrand wrote:
> On 24.05.19 14:29, Christian Borntraeger wrote:
>>
>>
>> On 24.05.19 14:17, Christian Borntraeger wrote:
>>>
>>>
>>> On 24.05.19 13:11, Christian Borntraeger wrote:
>>>> I do get
>>>>
>>>> [10400.440298] kvm-s390: failed to commit memory region
>>>> [10400.508723] kvm-s390: failed to commit memory region
>>>>
>>>> when running the tests. Will have a look.
>>>
>>> It comes from kvm_vm_free. This calls KVM_SET_USER_MEMORY_REGION with size 0,
>>> which the s390 code does not like.
>>>
>>
>> The doc says about  KVM_SET_USER_MEMORY_REGION:
>>
>> This ioctl allows the user to create or modify a guest physical memory
>> slot.  When changing an existing slot, it may be moved in the guest
>> physical memory space, or its flags may be modified.  --> It may not be
>> resized. <----
> 
> Size 0 is deleting, not resizing AFAIK.

Right this seems to translate to KVM_MR_DELETE, which the s390 code does not handle (we
will simply deliver a page fault as we share the last page table level). 
I will have a look at implementing KVM_MR_DELETE and KVM_MR_MOVE. In fact, we should
have a testcase for that as well.