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Tue, 7 Feb 2023 02:42:46 -0800 Message-ID: Date: Tue, 7 Feb 2023 18:42:44 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Subject: Re: [PATCH] mm: kfence: export kfence_enabled as global variables Content-Language: en-US To: Alexander Potapenko CC: Marco Elver , , , , , , Mark Rutland References: <1675750519-1064-1-git-send-email-quic_zhenhuah@quicinc.com> From: Zhenhua Huang In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01b.na.qualcomm.com (10.46.141.250) To nalasex01a.na.qualcomm.com (10.47.209.196) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-GUID: EFtdy1v4eFdo9Ed3rW9U9JTtrgGufCQ9 X-Proofpoint-ORIG-GUID: EFtdy1v4eFdo9Ed3rW9U9JTtrgGufCQ9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.930,Hydra:6.0.562,FMLib:17.11.122.1 definitions=2023-02-07_03,2023-02-06_03,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 lowpriorityscore=0 clxscore=1015 bulkscore=0 malwarescore=0 spamscore=0 mlxlogscore=737 adultscore=0 priorityscore=1501 phishscore=0 impostorscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2212070000 definitions=main-2302070095 X-Rspam-User: X-Rspamd-Queue-Id: 01E4BC000C X-Rspamd-Server: rspam01 X-Stat-Signature: nqf4rjmfauehbd74aa4d7d7fe8hozz6z X-HE-Tag: 1675766576-729975 X-HE-Meta: U2FsdGVkX195iTZyIZOEwMR3HBPGWXbkscWTdbq6Qo2HkYrtn0NsXAERMzZNnF4akvUmly+5VGoMs+AvqB4DFE33c0FyFBgJ2vVqL+gyr3qudj4p3gbKuAMYVvZekMwgSs0ZN0sAJiM6kll5dNaBDLo/fOtqxyf7uqgjfdVZf8rxhh0OQaxH5AQoKlFSDOkSpZiTbz1F+BYlycx7fhoxYDKyXlXNWsfpTf8LW0NYfO//DdFddGPy2ZuhYGPQGWpKM0ULYSNEfDNOQ6E4pviKOIyDY8hItcjOWxm4/36b4qlLsM1iouQFKbE4+jiCjUmui5lL2fq80RZ40IqOctTKziEy934OLJ3x0VUbwf1F92e8DhkJ7VWZfT/WRgXjpS9X96rRh1MG2gEQG4dLt9czC2DvyC8YOqtcyJtpOza+7v9J+dE6Il6/yS0dvw/ieDATpVCKcdGmBay/oU6VypMk88oAsZ9Dm6i9VPL/n/gwWpSeHJBNLpyqNbi4VLfsh/hhr1V+PLy7M4JzKwLoChep4kw63K5EakBd34Mq/dTvjDbBiArsugyK7e53ilvpa+zbPnb5EU0kNcRILg0Y6ewInZ7+FMLPWjXZXtx5KO3/aBlvIskY9yRWLNKfnYgCQXp+KH4ROzQswq/mCMOUU+Gzy0euu8rHocpunEBX1PDOhci5sAfdmLWVGIQ3kpI4mSNr/KZXJgqduONcKzrQLUJQMMz7Kuaxd2z9/z4xQ1n3h/JI95OEeocFfglNCQOkBZWD+U/l22do/aVyF2FKN3Y6cLQqjASORo8Vtpuf3jZUoO7PXtxvhxip9wMvouX95VPHlwT+bx+4IYyEVLgbDfn5KZiiLU7HpX8j65ikUyCte2S1Cw8AsxfaqU3nI38er8DMpZ7+lfqpNUNB5BdwZa+Gtu3agbxD/jscmeDwQA+fx9KtxQXWlKNR4/l/Y7ggciyPW6WOzH8Xlf2bRBKEs67 i9Mk9fUU hu7fGzOb2WFA8tw7Tb8Kbh1OkQwGdawk8doyBgtI+SJIIonuEvvSK68nAZ7BoZYnrI9KH4RXeoqXVXsNTdSSQ/w+Mqw5KGQYEyKSIZwe2PlON75TB0alhAXoJHlGISk1vxf97Wqyqxwd8YlhWA4/oMs0bTQV2o1oMuQz4mq5QTlLLPweYe6X/egPgAU4N/4AICNYZVeYIkHhka0mtx28nk/W6NjpoGqrgkRRQBsvZlhFQKOp/1VJIlQBvQY+kWhboJ387hyhwKmDI5HmQbLUm/HkM3Fs86doiSe8p X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2023/2/7 18:28, Alexander Potapenko wrote: >>> >>> What is the problem you have encountered? Is the page-granular direct >>> map causing issues? >> We're working on a low memory target, page-granular mapping costed more >> (2M per 1GB) memory. Due to GKI constraints, it is not easy to disable >> CONFIG_KFENCE. So my intention was to move the judgement to runtime >> configurable w/ CONFIG_KFENCE on... >> >> Do you have any further suggestion/proposal on this? Many Thanks! > > Right now CONFIG_KFENCE allocates 512Kb for the GKI kernel (only 63 > objects instead of the default 255): > https://cs.android.com/android/kernel/superproject/+/common-android-mainline:common/arch/arm64/configs/gki_defconfig;l=686?q=CONFIG_KFENCE_NUM_OBJECTS > Where do 2M come from? Hi Alexander, It is not from KFENCE cost itself, but from the requirement it needs page-granular mapping. 2M per 1GB cost is from linear mapping for page granularity. You can see can_set_direct_map() is used for whether allowing section mapping or not.