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Mon, 20 Jan 2025 10:28:50 +0000 (GMT) Date: Mon, 20 Jan 2025 11:28:48 +0100 From: Claudio Imbrenda To: David Hildenbrand Cc: Janosch Frank , kvm@vger.kernel.org, linux-s390@vger.kernel.org, borntraeger@de.ibm.com, schlameuss@linux.ibm.com, willy@infradead.org, hca@linux.ibm.com, svens@linux.ibm.com, agordeev@linux.ibm.com, gor@linux.ibm.com, nrb@linux.ibm.com, nsg@linux.ibm.com Subject: Re: [PATCH v1 13/13] KVM: s390: remove the last user of page->index Message-ID: <20250120112848.1547a439@p-imbrenda> In-Reply-To: References: <20250108181451.74383-1-imbrenda@linux.ibm.com> <20250108181451.74383-14-imbrenda@linux.ibm.com> <4175795f-9323-4a2c-acef-d387c104f8b3@linux.ibm.com> Organization: IBM X-Mailer: Claws Mail 4.3.0 (GTK 3.24.43; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: Z_52PMInAeRVQqyNwLHlx3Crh9sgqSS5 X-Proofpoint-GUID: Z_52PMInAeRVQqyNwLHlx3Crh9sgqSS5 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-01-20_02,2025-01-20_02,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 suspectscore=0 impostorscore=0 spamscore=0 mlxlogscore=999 bulkscore=0 phishscore=0 mlxscore=0 lowpriorityscore=0 priorityscore=1501 adultscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2501200087 On Mon, 20 Jan 2025 10:43:15 +0100 David Hildenbrand wrote: > >> +static inline unsigned long gmap_pgste_get_index(unsigned long *pgt) > >> +{ > >> + unsigned long *pgstes, res; > >> + > >> + pgstes = pgt + _PAGE_ENTRIES; > >> + > >> + res = (pgstes[0] & PGSTE_ST2_MASK) << 16; > >> + res |= pgstes[1] & PGSTE_ST2_MASK; > >> + res |= (pgstes[2] & PGSTE_ST2_MASK) >> 16; > >> + res |= (pgstes[3] & PGSTE_ST2_MASK) >> 32; > >> + > >> + return res; > >> +} > > > > I have to think about that change for a bit before I post an opinion. > > I'm wondering if we should just do what Willy suggested and use ptdesc > -> pt_index instead? we will need to store more stuff in the future; putting things in the PGSTEs gives us 512 bytes per table (although I admit it looks... weird) > > It's not like we must "force" this removal here. If we'll simply > allocate a ptdesc memdesc in the future for these page tables (just like > for any other page table), we have that extra space easily available. > > The important part is getting rid of page->index now, but not > necessarily ptdesc->pt_index. >