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Thu, 19 Aug 2021 13:53:28 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 106714203F; Thu, 19 Aug 2021 13:53:28 +0000 (GMT) Received: from li-7e0de7cc-2d9d-11b2-a85c-de26c016e5ad.ibm.com (unknown [9.171.33.59]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 19 Aug 2021 13:53:27 +0000 (GMT) Subject: Re: [PATCH 1/2] KVM: s390: gaccess: Cleanup access to guest frames To: Janosch Frank , David Hildenbrand , Janis Schoetterl-Glausch , kvm@vger.kernel.org, borntraeger@de.ibm.com, imbrenda@linux.ibm.com, Heiko Carstens , Vasily Gorbik Cc: cohuck@redhat.com, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210816150718.3063877-1-scgl@linux.ibm.com> <20210816150718.3063877-2-scgl@linux.ibm.com> <584ca757-4eb4-491e-a4cd-7bc60fb04b61@linux.ibm.com> From: Janis Schoetterl-Glausch Message-ID: <745fb5fc-175b-5920-5c56-db4ca8bc2488@linux.vnet.ibm.com> Date: Thu, 19 Aug 2021 15:53:27 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <584ca757-4eb4-491e-a4cd-7bc60fb04b61@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: JO-ys9WQ9C_0KGIWb19sObABLJNsxzEl X-Proofpoint-GUID: 4SXjLW5qvPKAUCJHqEvkASZcOROVDWhg X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-08-19_04:2021-08-17,2021-08-19 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=999 clxscore=1015 priorityscore=1501 malwarescore=0 impostorscore=0 mlxscore=0 phishscore=0 spamscore=0 bulkscore=0 lowpriorityscore=0 suspectscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108190079 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/18/21 10:06 AM, Janosch Frank wrote: > On 8/18/21 9:54 AM, David Hildenbrand wrote: >> On 16.08.21 17:07, Janis Schoetterl-Glausch wrote: >>> Introduce a helper function for guest frame access. >>> Rewrite the calculation of the gpa and the length of the segment >>> to be more readable. >>> >>> Signed-off-by: Janis Schoetterl-Glausch > [...] >>> - unsigned long _len, gpa; >>> + unsigned long gpa; >>> + unsigned int seg; >>> int rc = 0; >>> >>> while (len && !rc) { >>> gpa = kvm_s390_real_to_abs(vcpu, gra); >>> - _len = min(PAGE_SIZE - (gpa & ~PAGE_MASK), len); >>> - if (mode) >>> - rc = write_guest_abs(vcpu, gpa, data, _len); >>> - else >>> - rc = read_guest_abs(vcpu, gpa, data, _len); >>> - len -= _len; >>> - gra += _len; >>> - data += _len; >>> + seg = min(PAGE_SIZE - offset_in_page(gpa), len); >> >> What does "seg" mean? I certainly know when "len" means -- which is also >> what the function eats. > > What does "_len" mean especially in contrast to "len"? > > "seg" is used in the common kvm guest access functions so it's at least > consistent although I share the sentiment that it's not a great name for > the length we access inside the page. > > Originally I suggested "len_in_page" if you have a better name I'd > expect we'll both be happy to discuss it :-) fragment_len ? > >> >>> + rc = access_guest_frame(vcpu->kvm, mode, gpa, data, seg); >>> + len -= seg; >>> + gra += seg; >>> + data += seg; >>> } >>> return rc; >>> } >>> >> >> >