From: Will Deacon <will@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
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>,
Quentin Perret <qperret@google.com>, Tejun Heo <tj@kernel.org>,
Li Zefan <lizefan@huawei.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
kernel-team@android.com
Subject: [PATCH v5 13/15] arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system
Date: Tue, 8 Dec 2020 13:28:33 +0000 [thread overview]
Message-ID: <20201208132835.6151-14-will@kernel.org> (raw)
In-Reply-To: <20201208132835.6151-1-will@kernel.org>
If we want to support 32-bit applications, then when we identify a CPU
with mismatched 32-bit EL0 support we must ensure that we will always
have an active 32-bit CPU available to us from then on. This is important
for the scheduler, because is_cpu_allowed() will be constrained to 32-bit
CPUs for compat tasks and forced migration due to a hotplug event will
hang if no 32-bit CPUs are available.
On detecting a mismatch, prevent offlining of either the mismatching CPU
if it is 32-bit capable, or find the first active 32-bit capable CPU
otherwise.
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/kernel/cpufeature.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 088bf668cbe7..08b558a221b7 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1237,6 +1237,8 @@ has_cpuid_feature(const struct arm64_cpu_capabilities *entry, int scope)
static int enable_mismatched_32bit_el0(unsigned int cpu)
{
+ static int lucky_winner = -1;
+
struct cpuinfo_arm64 *info = &per_cpu(cpu_data, cpu);
bool cpu_32bit = id_aa64pfr0_32bit_el0(info->reg_id_aa64pfr0);
@@ -1245,6 +1247,22 @@ static int enable_mismatched_32bit_el0(unsigned int cpu)
static_branch_enable_cpuslocked(&arm64_mismatched_32bit_el0);
}
+ if (cpumask_test_cpu(0, cpu_32bit_el0_mask) == cpu_32bit)
+ return 0;
+
+ if (lucky_winner >= 0)
+ return 0;
+
+ /*
+ * We've detected a mismatch. We need to keep one of our CPUs with
+ * 32-bit EL0 online so that is_cpu_allowed() doesn't end up rejecting
+ * every CPU in the system for a 32-bit task.
+ */
+ lucky_winner = cpu_32bit ? cpu : cpumask_any_and(cpu_32bit_el0_mask,
+ cpu_active_mask);
+ get_cpu_device(lucky_winner)->offline_disabled = true;
+ pr_info("Asymmetric 32-bit EL0 support detected on CPU %u; CPU hot-unplug disabled on CPU %u\n",
+ cpu, lucky_winner);
return 0;
}
--
2.29.2.576.ga3fc446d84-goog
next prev parent reply other threads:[~2020-12-08 13:30 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-08 13:28 [PATCH v5 00/15] An alternative series for asymmetric AArch32 systems Will Deacon
2020-12-08 13:28 ` [PATCH v5 01/15] arm64: cpuinfo: Split AArch32 registers out into a separate struct Will Deacon
2020-12-08 13:28 ` [PATCH v5 02/15] arm64: Allow mismatched 32-bit EL0 support Will Deacon
2020-12-08 13:28 ` [PATCH v5 03/15] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched " Will Deacon
2020-12-08 13:28 ` [PATCH v5 04/15] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs Will Deacon
2020-12-08 13:28 ` [PATCH v5 05/15] arm64: Advertise CPUs capable of running 32-bit applications in sysfs Will Deacon
2020-12-08 13:28 ` [PATCH v5 06/15] sched: Introduce task_cpu_possible_mask() to limit fallback rq selection Will Deacon
2020-12-08 13:28 ` [PATCH v5 07/15] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 Will Deacon
2020-12-17 12:15 ` Qais Yousef
2020-12-17 13:44 ` Peter Zijlstra
2020-12-17 14:59 ` Will Deacon
2020-12-17 15:00 ` Qais Yousef
2020-12-08 13:28 ` [PATCH v5 08/15] cpuset: Honour task_cpu_possible_mask() in guarantee_online_cpus() Will Deacon
2020-12-28 3:54 ` Suren Baghdasaryan
2020-12-08 13:28 ` [PATCH v5 09/15] sched: Reject CPU affinity changes based on task_cpu_possible_mask() Will Deacon
2020-12-08 13:28 ` [PATCH v5 10/15] sched: Introduce force_compatible_cpus_allowed_ptr() to limit CPU affinity Will Deacon
2020-12-28 4:29 ` Suren Baghdasaryan
2020-12-08 13:28 ` [PATCH v5 11/15] arm64: Implement task_cpu_possible_mask() Will Deacon
2020-12-08 13:28 ` [PATCH v5 12/15] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 Will Deacon
2020-12-08 13:28 ` Will Deacon [this message]
2020-12-08 13:28 ` [PATCH v5 14/15] arm64: Hook up cmdline parameter to allow " Will Deacon
2020-12-08 13:28 ` [PATCH v5 15/15] arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores Will Deacon
2020-12-15 17:36 ` [PATCH v5 00/15] An alternative series for asymmetric AArch32 systems Peter Zijlstra
2020-12-15 18:50 ` Will Deacon
2020-12-17 10:55 ` Peter Zijlstra
2020-12-16 11:16 ` Qais Yousef
2020-12-16 14:14 ` Will Deacon
2020-12-16 16:48 ` Qais Yousef
2020-12-16 18:21 ` Suren Baghdasaryan
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