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Wed, 18 Aug 2021 08:48:52 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id EA28311C064; Wed, 18 Aug 2021 08:48:51 +0000 (GMT) Received: from li-7e0de7cc-2d9d-11b2-a85c-de26c016e5ad.ibm.com (unknown [9.171.50.49]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 18 Aug 2021 08:48:51 +0000 (GMT) Subject: Re: [PATCH 1/2] KVM: s390: gaccess: Cleanup access to guest frames To: David Hildenbrand , Janosch Frank , 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> <0c800ed3-cc60-9c13-c0a7-8ba302365ccb@redhat.com> From: Janis Schoetterl-Glausch Message-ID: <655a04b7-f73c-b2e4-026e-c361c545dd8e@linux.vnet.ibm.com> Date: Wed, 18 Aug 2021 10:48:51 +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: <0c800ed3-cc60-9c13-c0a7-8ba302365ccb@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: _iJ5KdRmlJJsN_v1haxfp9NrmKQLOng9 X-Proofpoint-GUID: n6wsFdFmwnLIsq7KpvMrXcfBqaQw-BQI X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-08-18_03:2021-08-17,2021-08-18 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 clxscore=1011 suspectscore=0 mlxscore=0 mlxlogscore=999 phishscore=0 priorityscore=1501 malwarescore=0 impostorscore=0 bulkscore=0 adultscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108180050 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/18/21 10:44 AM, David Hildenbrand wrote: > On 18.08.21 10:06, 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 :-) > > Similar code I encountered in other places uses "len" vs "cur_len" or "total_len" vs. "cur_len". I agree that everything is better than "len" vs. "_len". > > I just cannot come up with a proper word for "seg" that would make sense. "Segment" ? Maybe my uneducated mind is missing some important English words that just fit perfectly here. Yes, it's short for segment, kvm_main has a function next_segment to calculate it. I don't like the naming scheme much either. > > Anyhow, just my 2 cents, you maintain this code :) >