From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7BE1BC07E9D for ; Wed, 12 Oct 2022 20:56:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229924AbiJLU41 (ORCPT ); Wed, 12 Oct 2022 16:56:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40908 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229600AbiJLU4Z (ORCPT ); Wed, 12 Oct 2022 16:56:25 -0400 Received: from mx0b-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7014B5FDD5; Wed, 12 Oct 2022 13:56:23 -0700 (PDT) Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 29CKiOGm025705; Wed, 12 Oct 2022 20:56:19 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding; s=pp1; bh=JtDZIzJs+xc49I4Ma5TSfC98qmng9kM3z76Erhc9z1k=; b=VnnrrryYp/ogLC+po9UrWayZkMG51zoAaUpH5rYY/dg8ZEaPUvi2UA2UA1d+SXuT4o2s 3T7leUKuYZ2oke9yfoPZFHJwRuEQ2+c+gAviwjx+MLE1wfLpnp0Vmr2mZ/aTgru0B92T uXYOdUh2iA8nRu9+CDChv5tUcvt5/WcM8z5fUTDI8u4pW72OZuYxgjuTaJ99tb1JtG1v G4tnwrOFxyyqf0WwHpJhtj3vJQLrT/Ug2BDdvRLMtlpxwH495Ug3vw2MbBLAUmIVlVNQ v3jMCPnxa15OEtvTlmAHtBBTGehV57tWdPWIFs5dcoT0h7L5paZHleu190EHFoM3il3X eA== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3k62v1kj95-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 12 Oct 2022 20:56:18 +0000 Received: from m0098417.ppops.net (m0098417.ppops.net [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 29CKjFMe028334; Wed, 12 Oct 2022 20:56:18 GMT Received: from ppma04ams.nl.ibm.com (63.31.33a9.ip4.static.sl-reverse.com [169.51.49.99]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3k62v1kj8p-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 12 Oct 2022 20:56:18 +0000 Received: from pps.filterd (ppma04ams.nl.ibm.com [127.0.0.1]) by ppma04ams.nl.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 29CKqgP7002835; Wed, 12 Oct 2022 20:56:16 GMT Received: from b06cxnps4075.portsmouth.uk.ibm.com (d06relay12.portsmouth.uk.ibm.com [9.149.109.197]) by ppma04ams.nl.ibm.com with ESMTP id 3k30u9ejf9-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 12 Oct 2022 20:56:16 +0000 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 29CKuD2038469930 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 12 Oct 2022 20:56:13 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 348C75204F; Wed, 12 Oct 2022 20:56:13 +0000 (GMT) Received: from tuxmaker.boeblingen.de.ibm.com (unknown [9.152.85.9]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id B751D52050; Wed, 12 Oct 2022 20:56:12 +0000 (GMT) From: Janis Schoetterl-Glausch To: Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Heiko Carstens , Vasily Gorbik , Alexander Gordeev Cc: Janis Schoetterl-Glausch , 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 Subject: [PATCH v2 3/9] Documentation: KVM: s390: Describe KVM_S390_MEMOP_F_CMPXCHG Date: Wed, 12 Oct 2022 22:56:03 +0200 Message-Id: <20221012205609.2811294-4-scgl@linux.ibm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20221012205609.2811294-1-scgl@linux.ibm.com> References: <20221012205609.2811294-1-scgl@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: aSvPs4rdb94c3J65VVowectlYKjI5Lz7 X-Proofpoint-GUID: WMzB2R81i1pZlSCrXHca0BLmoMi-dcoz X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.545,FMLib:17.11.122.1 definitions=2022-10-12_10,2022-10-12_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 clxscore=1015 bulkscore=0 adultscore=0 mlxlogscore=773 phishscore=0 malwarescore=0 impostorscore=0 spamscore=0 lowpriorityscore=0 mlxscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2209130000 definitions=main-2210120131 Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Describe the semantics of the new KVM_S390_MEMOP_F_CMPXCHG flag for absolute vm write memops which allows user space to perform (storage key checked) cmpxchg operations on guest memory. Signed-off-by: Janis Schoetterl-Glausch --- Documentation/virt/kvm/api.rst | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index abd7c32126ce..f972f5d95e6c 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -3753,7 +3753,8 @@ The fields in each entry are defined as follows: :Parameters: struct kvm_s390_mem_op (in) :Returns: = 0 on success, < 0 on generic error (e.g. -EFAULT or -ENOMEM), - > 0 if an exception occurred while walking the page tables + 16 bit program exception code if the access causes such an exception + other code > maximum 16 bit value with special meaning Read or write data from/to the VM's memory. The KVM_CAP_S390_MEM_OP_EXTENSION capability specifies what functionality is @@ -3771,6 +3772,8 @@ Parameters are specified via the following structure:: struct { __u8 ar; /* the access register number */ __u8 key; /* access key, ignored if flag unset */ + __u8 pad1[6]; /* ignored */ + __u64 old_p; /* ignored if flag unset */ }; __u32 sida_offset; /* offset into the sida */ __u8 reserved[32]; /* ignored */ @@ -3853,8 +3856,22 @@ Absolute accesses are permitted for non-protected guests only. Supported flags: * ``KVM_S390_MEMOP_F_CHECK_ONLY`` * ``KVM_S390_MEMOP_F_SKEY_PROTECTION`` + * ``KVM_S390_MEMOP_F_CMPXCHG`` + +The semantics of the flags common with logical acesses are as for logical +accesses. + +For write accesses, the KVM_S390_MEMOP_F_CMPXCHG might be supported. +In this case, instead of doing an unconditional write, the access occurs only +if the target location contains the "size" byte long value pointed to by +"old_p". This is performed as an atomic cmpxchg. "size" must be a power of two +up to and including 16. +The value at the target location is written to the location "old_p" points to. +If the exchange did not take place because the target value doesn't match the +old value KVM_S390_MEMOP_R_NO_XCHG is returned. +The KVM_S390_MEMOP_F_CMPXCHG flag is supported if KVM_CAP_S390_MEM_OP_EXTENSION +has bit 1 (i.e. bit with value 2) set. -The semantics of the flags are as for logical accesses. SIDA read/write: ^^^^^^^^^^^^^^^^ -- 2.34.1