shinys000114/linux
1
0
Fork 0
mirror of https://github.com/hardkernel/linux.git synced 2026-06-07 11:26:02 +09:00
Code Issues Packages Projects Releases Wiki Activity

FROMLIST: arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system

Browse Source 
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>
Bug: 178507149
Link: https://lore.kernel.org/linux-arch/20201208132835.6151-14-will@kernel.org/
Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: I330859dfd7b10082e1a3dd5341d76f2a90b1f124
This commit is contained in:
Will Deacon
2020-11-12 21:01:59 +00:00
committed by Will Deacon
parent 90b7007bd6
commit e0c1be11f3
1 changed files with 18 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
arch/arm64/kernel/cpufeature.c
View File

@@ -1239,6 +1239,8 @@ 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);
@@ -1247,6 +1249,22 @@ 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;
}