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[91.12.100.23]) by smtp.gmail.com with ESMTPSA id n188sm3452655wmn.48.2021.08.18.01.44.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 18 Aug 2021 01:44:34 -0700 (PDT) Subject: Re: [PATCH 1/2] KVM: s390: gaccess: Cleanup access to guest frames To: 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> From: David Hildenbrand Organization: Red Hat Message-ID: <0c800ed3-cc60-9c13-c0a7-8ba302365ccb@redhat.com> Date: Wed, 18 Aug 2021 10:44:34 +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; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 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. Anyhow, just my 2 cents, you maintain this code :) -- Thanks, David / dhildenb