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Tue, 21 Jul 2020 21:37:42 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6E2D84C040; Tue, 21 Jul 2020 21:37:39 +0000 (GMT) Received: from oc0525413822.ibm.com (unknown [9.163.39.1]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Tue, 21 Jul 2020 21:37:39 +0000 (GMT) Date: Tue, 21 Jul 2020 14:37:36 -0700 From: Ram Pai To: Laurent Dufour Subject: Re: [PATCH v2 2/2] KVM: PPC: Book3S HV: rework secure mem slot dropping Message-ID: <20200721213736.GG7339@oc0525413822.ibm.com> References: <20200721104202.15727-1-ldufour@linux.ibm.com> <20200721104202.15727-3-ldufour@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200721104202.15727-3-ldufour@linux.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-07-21_15:2020-07-21, 2020-07-21 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 lowpriorityscore=0 suspectscore=0 bulkscore=0 adultscore=0 clxscore=1015 priorityscore=1501 mlxscore=0 mlxlogscore=328 phishscore=0 impostorscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007210138 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Ram Pai Cc: linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org, bharata@linux.ibm.com, paulus@samba.org, sukadev@linux.ibm.com, linuxppc-dev@lists.ozlabs.org, bauerman@linux.ibm.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, Jul 21, 2020 at 12:42:02PM +0200, Laurent Dufour wrote: > When a secure memslot is dropped, all the pages backed in the secure device > (aka really backed by secure memory by the Ultravisor) should be paged out > to a normal page. Previously, this was achieved by triggering the page > fault mechanism which is calling kvmppc_svm_page_out() on each pages. > > This can't work when hot unplugging a memory slot because the memory slot > is flagged as invalid and gfn_to_pfn() is then not trying to access the > page, so the page fault mechanism is not triggered. > > Since the final goal is to make a call to kvmppc_svm_page_out() it seems > simpler to directly calling it instead of triggering such a mechanism. This ^^ call directly instead of triggering.. > way kvmppc_uvmem_drop_pages() can be called even when hot unplugging a > memslot. > > Since kvmppc_uvmem_drop_pages() is already holding kvm->arch.uvmem_lock, > the call to __kvmppc_svm_page_out() is made. > As __kvmppc_svm_page_out needs the vma pointer to migrate the pages, the > VMA is fetched in a lazy way, to not trigger find_vma() all the time. In > addition, the mmap_sem is help in read mode during that time, not in write ^^ held > mode since the virual memory layout is not impacted, and > kvm->arch.uvmem_lock prevents concurrent operation on the secure device. > > Cc: Ram Pai Reviewed-by: Ram Pai RP