From: Catalin Marinas <catalin.marinas@arm.com> To: Will Deacon <will@kernel.org> Cc: "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>, Marc Zyngier <maz@kernel.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Peter Zijlstra <peterz@infradead.org>, Morten Rasmussen <Morten.Rasmussen@arm.com>, Qais Yousef <Qais.Yousef@arm.com>, Suren Baghdasaryan <surenb@google.com>, "kernel-team@android.com" <kernel-team@android.com> Subject: Re: [PATCH 2/6] arm64: Allow mismatched 32-bit EL0 support Date: Fri, 6 Nov 2020 14:30:21 +0000 [thread overview] Message-ID: <20201106143020.GG29329@gaia> (raw) In-Reply-To: <20201105213846.GA8600@willie-the-truck> On Thu, Nov 05, 2020 at 09:38:46PM +0000, Will Deacon wrote: > Ok. Then we're in agreement about not preventing late-onlining. The problem > then is that the existing 32-bit EL0 capability is a SYSTEM cap so even with > your diff, we still have an issue if you boot on the CPUs that support > 32-bit and then try to online a 64-bit-only core (it will fail). Ah, I focussed too much on the 32-bit capable CPUs coming up late. In my original hack, I made the capability weak based on the config option. Here we want to make it weak based on cmdline but that structure is const (we could remove the const though). > So I think we do need my changes to the existing cap, but perhaps we > could return false from system_supports_32bit_el0() until we've actually > seen a 32-bit capable core. That way you would keep the existing behaviour > on TX2, and we wouldn't get any unusual late-onlining failures. If we see the first 32-bit capable core late, we may report it's available but no proper hwcaps. We could do a combination of a new weak feature together with your always-on 32-bit feature when forced by the cmdline. So the system would support 32-bit if both the system feature (with the detection override) and the asym one are set. However, I think it may be simpler if we made the current feature weak (so no new one) together with a bool somewhere that tells us if we found a CPU that doesn't have 32-bit (asym mode). system_supports_32bit_el0() would check if the cap is set together with (!asym_found || asym_allowed). -- Catalin
WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com> To: Will Deacon <will@kernel.org> Cc: "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>, "kernel-team@android.com" <kernel-team@android.com>, Peter Zijlstra <peterz@infradead.org>, Marc Zyngier <maz@kernel.org>, Qais Yousef <Qais.Yousef@arm.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Suren Baghdasaryan <surenb@google.com>, Morten Rasmussen <Morten.Rasmussen@arm.com>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org> Subject: Re: [PATCH 2/6] arm64: Allow mismatched 32-bit EL0 support Date: Fri, 6 Nov 2020 14:30:21 +0000 [thread overview] Message-ID: <20201106143020.GG29329@gaia> (raw) In-Reply-To: <20201105213846.GA8600@willie-the-truck> On Thu, Nov 05, 2020 at 09:38:46PM +0000, Will Deacon wrote: > Ok. Then we're in agreement about not preventing late-onlining. The problem > then is that the existing 32-bit EL0 capability is a SYSTEM cap so even with > your diff, we still have an issue if you boot on the CPUs that support > 32-bit and then try to online a 64-bit-only core (it will fail). Ah, I focussed too much on the 32-bit capable CPUs coming up late. In my original hack, I made the capability weak based on the config option. Here we want to make it weak based on cmdline but that structure is const (we could remove the const though). > So I think we do need my changes to the existing cap, but perhaps we > could return false from system_supports_32bit_el0() until we've actually > seen a 32-bit capable core. That way you would keep the existing behaviour > on TX2, and we wouldn't get any unusual late-onlining failures. If we see the first 32-bit capable core late, we may report it's available but no proper hwcaps. We could do a combination of a new weak feature together with your always-on 32-bit feature when forced by the cmdline. So the system would support 32-bit if both the system feature (with the detection override) and the asym one are set. However, I think it may be simpler if we made the current feature weak (so no new one) together with a bool somewhere that tells us if we found a CPU that doesn't have 32-bit (asym mode). system_supports_32bit_el0() would check if the cap is set together with (!asym_found || asym_allowed). -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-11-06 14:30 UTC|newest] Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-10-27 21:51 [PATCH 0/6] An alternative series for asymmetric AArch32 systems Will Deacon 2020-10-27 21:51 ` Will Deacon 2020-10-27 21:51 ` [PATCH 1/6] KVM: arm64: Handle Asymmetric " Will Deacon 2020-10-27 21:51 ` Will Deacon 2020-10-27 21:51 ` [PATCH 2/6] arm64: Allow mismatched 32-bit EL0 support Will Deacon 2020-10-27 21:51 ` Will Deacon 2020-10-28 11:12 ` Catalin Marinas 2020-10-28 11:12 ` Catalin Marinas 2020-10-28 11:17 ` Will Deacon 2020-10-28 11:17 ` Will Deacon 2020-10-28 11:22 ` Catalin Marinas 2020-10-28 11:22 ` Catalin Marinas 2020-10-28 11:23 ` Will Deacon 2020-10-28 11:23 ` Will Deacon 2020-10-28 11:49 ` Catalin Marinas 2020-10-28 11:49 ` Catalin Marinas 2020-10-28 12:40 ` Will Deacon 2020-10-28 12:40 ` Will Deacon 2020-10-28 18:56 ` Catalin Marinas 2020-10-28 18:56 ` Catalin Marinas 2020-10-29 22:20 ` Will Deacon 2020-10-29 22:20 ` Will Deacon 2020-10-30 11:18 ` Catalin Marinas 2020-10-30 11:18 ` Catalin Marinas 2020-10-30 16:13 ` Will Deacon 2020-10-30 16:13 ` Will Deacon 2020-11-02 11:44 ` Catalin Marinas 2020-11-02 11:44 ` Catalin Marinas 2020-11-05 21:38 ` Will Deacon 2020-11-05 21:38 ` Will Deacon 2020-11-06 12:54 ` Qais Yousef 2020-11-06 12:54 ` Qais Yousef 2020-11-06 13:00 ` Will Deacon 2020-11-06 13:00 ` Will Deacon 2020-11-06 14:48 ` Qais Yousef 2020-11-06 14:48 ` Qais Yousef 2020-11-09 13:52 ` Will Deacon 2020-11-09 13:52 ` Will Deacon 2020-11-11 16:27 ` Qais Yousef 2020-11-11 16:27 ` Qais Yousef 2020-11-12 10:24 ` Will Deacon 2020-11-12 10:24 ` Will Deacon 2020-11-12 11:55 ` Qais Yousef 2020-11-12 11:55 ` Qais Yousef 2020-11-12 16:49 ` Qais Yousef 2020-11-12 16:49 ` Qais Yousef 2020-11-12 17:06 ` Marc Zyngier 2020-11-12 17:06 ` Marc Zyngier 2020-11-12 17:36 ` Qais Yousef 2020-11-12 17:36 ` Qais Yousef 2020-11-12 17:44 ` Will Deacon 2020-11-12 17:44 ` Will Deacon 2020-11-12 17:36 ` Will Deacon 2020-11-12 17:36 ` Will Deacon 2020-11-13 10:45 ` Qais Yousef 2020-11-13 10:45 ` Qais Yousef 2020-11-06 14:30 ` Catalin Marinas [this message] 2020-11-06 14:30 ` Catalin Marinas 2020-10-28 11:18 ` Catalin Marinas 2020-10-28 11:18 ` Catalin Marinas 2020-10-28 11:21 ` Will Deacon 2020-10-28 11:21 ` Will Deacon 2020-10-27 21:51 ` [PATCH 3/6] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched " Will Deacon 2020-10-27 21:51 ` Will Deacon 2020-10-27 21:51 ` [PATCH 4/6] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs Will Deacon 2020-10-27 21:51 ` Will Deacon 2020-10-28 12:10 ` Catalin Marinas 2020-10-28 12:10 ` Catalin Marinas 2020-10-28 12:36 ` Will Deacon 2020-10-28 12:36 ` Will Deacon 2020-10-27 21:51 ` [PATCH 5/6] arm64: Advertise CPUs capable of running 32-bit applcations in sysfs Will Deacon 2020-10-27 21:51 ` Will Deacon 2020-10-28 8:37 ` Greg Kroah-Hartman 2020-10-28 8:37 ` Greg Kroah-Hartman 2020-10-28 9:51 ` Will Deacon 2020-10-28 9:51 ` Will Deacon 2020-10-28 12:15 ` Catalin Marinas 2020-10-28 12:15 ` Catalin Marinas 2020-10-28 12:27 ` Will Deacon 2020-10-28 12:27 ` Will Deacon 2020-10-28 15:14 ` Catalin Marinas 2020-10-28 15:14 ` Catalin Marinas 2020-10-28 15:35 ` Will Deacon 2020-10-28 15:35 ` Will Deacon 2020-10-27 21:51 ` [PATCH 6/6] arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0 Will Deacon 2020-10-27 21:51 ` Will Deacon 2020-10-29 18:42 ` [PATCH 0/6] An alternative series for asymmetric AArch32 systems Suren Baghdasaryan 2020-10-29 18:42 ` Suren Baghdasaryan 2020-10-29 22:17 ` Will Deacon 2020-10-29 22:17 ` Will Deacon 2020-10-30 16:16 ` Marc Zyngier 2020-10-30 16:16 ` Marc Zyngier 2020-10-30 16:24 ` Will Deacon 2020-10-30 16:24 ` Will Deacon 2020-10-30 17:04 ` Marc Zyngier 2020-10-30 17:04 ` Marc Zyngier
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