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Tue, 17 Oct 2023 19:01:33 +0100 Date: Tue, 17 Oct 2023 19:01:31 +0100 Message-ID: <86ttqpm8lg.wl-maz@kernel.org> From: Marc Zyngier To: Jeremy Linton Cc: linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, anshuman.khandual@arm.com, krisman@suse.de, broonie@kernel.org, james.morse@arm.com, ionela.voinescu@arm.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/3] arm64: cpufeature: Change 32-bit EL0 to display enabled cores In-Reply-To: <20231017052322.1211099-4-jeremy.linton@arm.com> References: <20231017052322.1211099-1-jeremy.linton@arm.com> <20231017052322.1211099-4-jeremy.linton@arm.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/29.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: jeremy.linton@arm.com, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, anshuman.khandual@arm.com, krisman@suse.de, broonie@kernel.org, james.morse@arm.com, ionela.voinescu@arm.com, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231017_110141_563967_1A87666D X-CRM114-Status: GOOD ( 23.25 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 17 Oct 2023 06:23:22 +0100, Jeremy Linton wrote: > > Now that we have the ability to display the list of cores > with a feature when it is selectivly enabled, lets display the > cores enabled for 32-bit use at EL0. > > Signed-off-by: Jeremy Linton > --- > arch/arm64/kernel/cpufeature.c | 15 +++++++++++++-- > 1 file changed, 13 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index b7b67bac0e60..512cbe446b41 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -1533,8 +1533,17 @@ static bool has_32bit_el0(const struct arm64_cpu_capabilities *entry, int scope) > if (!has_cpuid_feature(entry, scope)) > return allow_mismatched_32bit_el0; > > - if (scope == SCOPE_SYSTEM) > - pr_info("detected: 32-bit EL0 Support\n"); > + if (scope == SCOPE_SYSTEM) { > + struct arm64_cpu_capabilities *has_32bit; > + > + has_32bit = (struct arm64_cpu_capabilities *)entry; > + > + has_32bit->cpus = system_32bit_el0_cpumask(); This seems rather dodgy. 'entry' comes from a static const array which will, in all likelihood be mapped R/O pretty soon after the initial CPU bringup. Try offlining/onlining a CPU and you should see a firework similar to what I have below (I hacked the CnP property, but that's no different from what you are doing): bash-5.1# echo 0 >/sys/devices/system/cpu/cpu2/online [ 51.367137] psci: CPU2 killed (polled 0 ms) bash-5.1# echo 1 >/sys/devices/system/cpu/cpu2/online [ 56.703092] Unable to handle kernel write to read-only memory at virtual address ffff800080d63db0 [ 56.703494] Mem abort info: [ 56.703627] ESR = 0x000000009600004f [ 56.703799] EC = 0x25: DABT (current EL), IL = 32 bits [ 56.704052] SET = 0, FnV = 0 [ 56.704196] EA = 0, S1PTW = 0 [ 56.704340] FSC = 0x0f: level 3 permission fault [ 56.704575] Data abort info: [ 56.704715] ISV = 0, ISS = 0x0000004f, ISS2 = 0x00000000 [ 56.704961] CM = 0, WnR = 1, TnD = 0, TagAccess = 0 [ 56.705195] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [ 56.705435] swapper pgtable: 4k pages, 48-bit VAs, pgdp=000000008142e000 [ 56.705742] [ffff800080d63db0] pgd=10000000dbfff003, p4d=10000000dbfff003, pud=10000000dbffe003, pmd=10000000dbffc003, pte=0060000080d63783 [ 56.706310] Internal error: Oops: 000000009600004f [#1] PREEMPT SMP [ 56.706591] Modules linked in: [ 56.706741] CPU: 2 PID: 0 Comm: swapper/2 Not tainted 6.6.0-rc1-00007-g805cc7d30885-dirty #1702 [ 56.707145] Hardware name: linux,dummy-virt (DT) [ 56.707359] pstate: 800001c5 (Nzcv dAIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 56.707676] pc : cpu_enable_cnp+0x24/0x60 [ 56.707873] lr : verify_local_cpu_caps+0x6c/0x140 [ 56.708046] sp : ffff800082103e10 [ 56.708201] x29: ffff800082103e10 x28: 0000000000000000 x27: 0000000000000000 [ 56.708517] x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000 [ 56.708837] x23: ffff800081eec540 x22: 0000000000000003 x21: ffff8000813945f0 [ 56.709166] x20: ffff800081394358 x19: ffff800080d63db0 x18: 0000000000000000 [ 56.709488] x17: 000000040044ffff x16: 00500073b5503510 x15: 0000000000000000 [ 56.709805] x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 [ 56.710100] x11: 0000000000000000 x10: 0000000000000000 x9 : ffff8000800273ac [ 56.710416] x8 : ffff80008003b640 x7 : 0000000000000000 x6 : 0000000000000000 [ 56.710738] x5 : 0000000000000000 x4 : ffff800081394000 x3 : ffff800081394000 [ 56.711070] x2 : ffff800081241ef8 x1 : ffff800080027218 x0 : ffff800080d63db0 [ 56.711396] Call trace: [ 56.711512] cpu_enable_cnp+0x24/0x60 [ 56.711684] verify_local_cpu_caps+0x6c/0x140 [ 56.711885] verify_local_cpu_capabilities+0x1c/0x198 [ 56.712112] check_local_cpu_capabilities+0x28/0x50 [ 56.712337] secondary_start_kernel+0xb4/0x1a0 [ 56.712546] __secondary_switched+0xb8/0xc0 [ 56.712739] Code: 910003fd b0009b63 d00090c2 913be042 (f9000002) [ 56.713013] ---[ end trace 0000000000000000 ]--- [ 56.713224] Kernel panic - not syncing: Attempted to kill the idle task! [ 56.713518] SMP: stopping secondary CPUs [ 56.713752] Kernel Offset: disabled [ 56.713908] CPU features: 0x00000000,50024d43,1947f723 [ 56.714144] Memory Limit: none [ 56.714292] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]--- Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel