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Tue, 4 Oct 2022 13:47:43 +0000 (GMT) Received: from [9.145.154.3] (unknown [9.145.154.3]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 4 Oct 2022 13:47:43 +0000 (GMT) Message-ID: <93dbe028-eb4b-7620-58c9-d1fb8e0431ca@linux.ibm.com> Date: Tue, 4 Oct 2022 15:47:43 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.1 Subject: Re: [PATCH v14 4/6] KVM: s390: pv: avoid export before import if possible Content-Language: en-US To: Claudio Imbrenda , kvm@vger.kernel.org Cc: borntraeger@de.ibm.com, frankja@linux.ibm.com, thuth@redhat.com, david@redhat.com, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, scgl@linux.ibm.com, nrb@linux.ibm.com References: <20220930140150.37463-1-imbrenda@linux.ibm.com> <20220930140150.37463-5-imbrenda@linux.ibm.com> From: Steffen Eiden In-Reply-To: <20220930140150.37463-5-imbrenda@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: MMCP-zgIEwDKNSxW8N0rPygT3alerQJ0 X-Proofpoint-GUID: Gz0wkrRTuqY3KmWdLOB0VSQa8n3uIekL X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.528,FMLib:17.11.122.1 definitions=2022-10-04_06,2022-09-29_03,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 suspectscore=0 bulkscore=0 adultscore=0 mlxlogscore=999 spamscore=0 lowpriorityscore=0 priorityscore=1501 clxscore=1015 mlxscore=0 impostorscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2209130000 definitions=main-2210040088 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 9/30/22 16:01, Claudio Imbrenda wrote: > If the appropriate UV feature bit is set, there is no need to perform > an export before import. > > The misc feature indicates, among other things, that importing a shared > page from a different protected VM will automatically also transfer its > ownership. > > Signed-off-by: Claudio Imbrenda > Reviewed-by: Nico Boehr > Reviewed-by: Janosch Frank LGTM Reviewed-by: Steffen Eiden > --- > arch/s390/kernel/uv.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c > index f9810d2a267c..9f18a4af9c13 100644 > --- a/arch/s390/kernel/uv.c > +++ b/arch/s390/kernel/uv.c > @@ -255,6 +255,13 @@ 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, among other things, that importing a > + * shared page from a different protected VM will automatically also > + * transfer its ownership. > + */ > + 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;