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Wed, 4 Oct 2023 05:12:20 +0000 (GMT) Message-ID: <6e636e70-cbe5-45a7-8918-abdf196d5437@linux.ibm.com> Date: Wed, 4 Oct 2023 10:42:20 +0530 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 2/2] dax/kmem: allow kmem to add memory with memmap_on_memory Content-Language: en-US To: "Verma, Vishal L" , "Williams, Dan J" , "Jiang, Dave" , "osalvador@suse.de" , "david@redhat.com" , "akpm@linux-foundation.org" Cc: "Hocko, Michal" , "Huang, Ying" , "Jonathan.Cameron@Huawei.com" , "linux-cxl@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "jmoyer@redhat.com" , "dave.hansen@linux.intel.com" , "linux-mm@kvack.org" , "nvdimm@lists.linux.dev" References: <20230928-vv-kmem_memmap-v4-0-6ff73fec519a@intel.com> <20230928-vv-kmem_memmap-v4-2-6ff73fec519a@intel.com> <73bdc58d-edc1-4344-b42a-4b83ca885329@linux.ibm.com> From: Aneesh Kumar K V In-Reply-To: Content-Type: text/plain; charset=UTF-8 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: lwr6gmcUVDz9kvKRX2_JLfm8fM4InJpt X-Proofpoint-ORIG-GUID: q9xukhjGvTEJd5H1i7EYqmnB_Vay5YoE Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.267,Aquarius:18.0.980,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-10-04_01,2023-10-02_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 mlxlogscore=664 malwarescore=0 impostorscore=0 adultscore=0 bulkscore=0 suspectscore=0 clxscore=1015 mlxscore=0 phishscore=0 spamscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2309180000 definitions=main-2310040035 Precedence: bulk List-ID: X-Mailing-List: linux-cxl@vger.kernel.org On 10/4/23 5:18 AM, Verma, Vishal L wrote: > On Tue, 2023-10-03 at 09:34 +0530, Aneesh Kumar K V wrote: >> On 9/29/23 2:00 AM, Vishal Verma wrote: >>> Large amounts of memory managed by the kmem driver may come in via CXL, >>> and it is often desirable to have the memmap for this memory on the new >>> memory itself. >>> >>> Enroll kmem-managed memory for memmap_on_memory semantics if the dax >>> region originates via CXL. For non-CXL dax regions, retain the existing >>> default behavior of hot adding without memmap_on_memory semantics. >>> >> >> Are we not looking at doing altmap space for CXL DAX regions? Last discussion around >> this was suggesting we look at doing this via altmap reservation so that >> we get contigous space for device memory enabling us to map them >> via 1G direct mapping entries? >> > Hey Aneesh - was this on a previous posting or something - do you have > a link so I can refresh myself on what the discussion was? > > If it is enabling something in CXL similar to the --map=mem mode for > pmem + device dax, that could be incremental to this. Yes. Agree that we can do that incremental to this. https://lore.kernel.org/linux-mm/b6753402-2de9-25b2-36e9-eacd49752b19@redhat.com -aneesh