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Fri, 19 Aug 2022 09:51:14 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6D35CAE051; Fri, 19 Aug 2022 09:50:55 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D93D7AE045; Fri, 19 Aug 2022 09:50:54 +0000 (GMT) Received: from [9.145.49.220] (unknown [9.145.49.220]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 19 Aug 2022 09:50:54 +0000 (GMT) Message-ID: <99a49638-1604-962e-9010-1b57111d3132@linux.ibm.com> Date: Fri, 19 Aug 2022 11:50:54 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 Content-Language: en-US To: Claudio Imbrenda , kvm@vger.kernel.org Cc: borntraeger@de.ibm.com, thuth@redhat.com, pasic@linux.ibm.com, david@redhat.com, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, scgl@linux.ibm.com, seiden@linux.ibm.com, nrb@linux.ibm.com References: <20220810125625.45295-1-imbrenda@linux.ibm.com> <20220810125625.45295-5-imbrenda@linux.ibm.com> From: Janosch Frank Subject: Re: [PATCH v13 4/6] KVM: s390: pv: avoid export before import if possible In-Reply-To: <20220810125625.45295-5-imbrenda@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: NNgj39bwebWjNUdU7YYEarOHQPvFevST X-Proofpoint-ORIG-GUID: qPlsnErocGN7hRNExndp0u-nGtAuWj4g X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.517,FMLib:17.11.122.1 definitions=2022-08-19_04,2022-08-18_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 phishscore=0 adultscore=0 mlxlogscore=999 malwarescore=0 priorityscore=1501 spamscore=0 lowpriorityscore=0 impostorscore=0 mlxscore=0 clxscore=1015 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2207270000 definitions=main-2208190037 X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_EF,NICE_REPLY_A,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/10/22 14:56, Claudio Imbrenda wrote: > If the appropriate UV feature bit is set, there is no need to perform > an export before import. > > Signed-off-by: Claudio Imbrenda > Reviewed-by: Nico Boehr > --- > arch/s390/kernel/uv.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c > index f9810d2a267c..b455646c8d74 100644 > --- a/arch/s390/kernel/uv.c > +++ b/arch/s390/kernel/uv.c > @@ -255,6 +255,8 @@ static int make_secure_pte(pte_t *ptep, unsigned long addr, > */ > static bool should_export_before_import(struct uv_cb_header *uvcb, struct mm_struct *mm) > { The misc feature indicates that the UV will automatically transfer ownership from one protected VM to another when importing a shared page. Other than that: Reviewed-by: Janosch Frank > + if (test_bit_inv(BIT_UV_FEAT_MISC, &uv_info.uv_feature_indications)) > + return false; > if (uvcb->cmd == UVC_CMD_UNPIN_PAGE_SHARED) > return false; > return atomic_read(&mm->context.protected_count) > 1;