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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1724431208; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oN87FP2CLweOxVCzRwR4t8EmbAa3c0hPfA2xu+5mcvY=; b=roq9E3XOV53a2ehZKY6+qf71sbsAeQtFBSzV/utsfMviLAxxaO8Z9VQHjhZg+ZvGq9szJw S0FRRdiNQ2iKW01QudJlVHEKfoQGHWmXP1UdqTsUN5y1StvSxUgEk75PGnJn6JOZPWvWVW fu+uKSj2AprUzMQfJJ9jRM4I6DsNqnM= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id D918E6123B; Fri, 23 Aug 2024 16:41:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CBB56C32786; Fri, 23 Aug 2024 16:41:08 +0000 (UTC) Date: Fri, 23 Aug 2024 17:41:06 +0100 From: Catalin Marinas To: Will Deacon Cc: Joey Gouly , linux-arm-kernel@lists.infradead.org, nd@arm.com, akpm@linux-foundation.org, aneesh.kumar@kernel.org, aneesh.kumar@linux.ibm.com, anshuman.khandual@arm.com, bp@alien8.de, broonie@kernel.org, christophe.leroy@csgroup.eu, dave.hansen@linux.intel.com, hpa@zytor.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, maz@kernel.org, mingo@redhat.com, mpe@ellerman.id.au, naveen.n.rao@linux.ibm.com, npiggin@gmail.com, oliver.upton@linux.dev, shuah@kernel.org, skhan@linuxfoundation.org, szabolcs.nagy@arm.com, tglx@linutronix.de, x86@kernel.org, kvmarm@lists.linux.dev, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v5 06/30] arm64: context switch POR_EL0 register Message-ID: References: <20240822151113.1479789-1-joey.gouly@arm.com> <20240822151113.1479789-7-joey.gouly@arm.com> <20240823144531.GH32156@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240823144531.GH32156@willie-the-truck> X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 665A240021 X-Stat-Signature: jth5u9wkrofjm9ejymo8c3jxd79y6fg7 X-Rspam-User: X-HE-Tag: 1724431275-962431 X-HE-Meta: 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 IhtBch+j ZnZGo5k9ewS51KnVMcE5OfT3hwUFWK+EC4313KpHHxV6reInz/P7QSC92W8usvJ5gGCcV63Hx7z37m9rfI2MqendBhu+sLo78i5aH8fGVPGSDdtxTUNOI5Fe51AunQW/t7iYEtJe3CDjwj+tcJP6Vg+CQKITKTd4v4BTPbzhjm5YY4iutVJzCBRlAC/bqubmR44uVuVmLfhhh79ohfbPjkLSHnv2L7VSQBpMuWgszNKfxZxnZmWQVEw/cgxBQXVcSHvpdgtO01IKMa1u3ufCezE9qR+CR+RPoQe/eB+fMVH/9HyVorsOIsY6vERiYVsh+9ejTcZWpHyIUHhsBDZPtXtmZaFD+FWezwQKTnsoi7AfSIgHha9ln/syTB2wCSiheUC7ncQcSD+SP7aY= 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: List-Subscribe: List-Unsubscribe: On Fri, Aug 23, 2024 at 03:45:32PM +0100, Will Deacon wrote: > On Thu, Aug 22, 2024 at 04:10:49PM +0100, Joey Gouly wrote: > > +static void permission_overlay_switch(struct task_struct *next) > > +{ > > + if (!system_supports_poe()) > > + return; > > + > > + current->thread.por_el0 = read_sysreg_s(SYS_POR_EL0); > > + if (current->thread.por_el0 != next->thread.por_el0) { > > + write_sysreg_s(next->thread.por_el0, SYS_POR_EL0); > > + /* ISB required for kernel uaccess routines when chaning POR_EL0 */ > > nit: typo "chaning". > > But more substantially, is this just to prevent spurious faults in the > context of a new thread using a stale value for POR_EL0? Not just prevent faults but enforce the permissions from the new thread's POR_EL0. The kernel may continue with a uaccess routine from here, we can't tell. -- Catalin