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Wed, 11 Jan 2023 09:38:28 +0000 (GMT) Message-ID: <10ba824d-6174-2fc4-b58b-a914cc5524be@linux.ibm.com> Date: Wed, 11 Jan 2023 10:38:28 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [PATCH v5 01/10] KVM: s390: Extend MEM_OP ioctl by storage key checked cmpxchg Content-Language: en-US To: Janis Schoetterl-Glausch , Christian Borntraeger , Claudio Imbrenda , Heiko Carstens , Vasily Gorbik , Alexander Gordeev Cc: David Hildenbrand , Jonathan Corbet , kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-s390@vger.kernel.org, Paolo Bonzini , Shuah Khan , Sven Schnelle References: <20230110202632.2533978-1-scgl@linux.ibm.com> <20230110202632.2533978-2-scgl@linux.ibm.com> From: Janosch Frank In-Reply-To: <20230110202632.2533978-2-scgl@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: CNwXYW343tftih-Q8VSAGH_KywNKeO-- X-Proofpoint-GUID: a-YGHPhU_EzZ5t_qoeYF_xDAeRzlCnrd X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.923,Hydra:6.0.545,FMLib:17.11.122.1 definitions=2023-01-11_04,2023-01-10_03,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 mlxlogscore=999 phishscore=0 adultscore=0 spamscore=0 suspectscore=0 bulkscore=0 malwarescore=0 impostorscore=0 mlxscore=0 lowpriorityscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2212070000 definitions=main-2301110073 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 1/10/23 21:26, Janis Schoetterl-Glausch wrote: > User space can use the MEM_OP ioctl to make storage key checked reads > and writes to the guest, however, it has no way of performing atomic, > key checked, accesses to the guest. > Extend the MEM_OP ioctl in order to allow for this, by adding a cmpxchg > mode. For now, support this mode for absolute accesses only. > > This mode can be use, for example, to set the device-state-change > indicator and the adapter-local-summary indicator atomically. > > Signed-off-by: Janis Schoetterl-Glausch > --- > include/uapi/linux/kvm.h | 7 +++ > arch/s390/kvm/gaccess.h | 3 ++ > arch/s390/kvm/gaccess.c | 102 +++++++++++++++++++++++++++++++++++++++ > arch/s390/kvm/kvm-s390.c | 41 +++++++++++++++- > 4 files changed, 151 insertions(+), 2 deletions(-) > > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > index 55155e262646..452f43c1cc34 100644 > --- a/include/uapi/linux/kvm.h > +++ b/include/uapi/linux/kvm.h > @@ -583,6 +583,8 @@ struct kvm_s390_mem_op { > struct { > __u8 ar; /* the access register number */ > __u8 key; /* access key, ignored if flag unset */ > + __u8 pad1[6]; /* ignored */ > + __u64 old_addr; /* ignored if flag unset */ These 3 are only used for flag values >=4, no? They aren't used for all flag values but for specific ones, right?