From: Jan Kiszka <jan.kis...@siemens.com>
First of all, this erratum hook is called from __switch_to, thus
potentially also from the primary domain. Some of the functions it calls
check if preemption was disabled under Linux - which may not be the case
when invoked from primary domain. Rather than adding a costly check for
ipipe_root_p to this hot-path, simply turn the check off if I-pipe is
enabled.
As the hook can be called from primary context, we need to protect its
setup for new execs against those contexts via hard_preempt_disable.
Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>
---
This is for 5.4-only, older kernels do no have the erratum fix.
Philippe, the hardening of erratum_1418040_new_exec() could be a topic
for dovetail as well. preemptible() is fully oob-aware there, though.
arch/arm64/kernel/cpu_errata.c | 3 ++-
arch/arm64/kernel/cpufeature.c | 3 ++-
arch/arm64/kernel/process.c | 4 ++--
3 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 1e16c4e00e771..7fd7d1c8b9fcc 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -37,7 +37,8 @@ static bool __maybe_unused
is_affected_midr_range_list(const struct arm64_cpu_capabilities *entry,
int scope)
{
- WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible());
+ WARN_ON(scope != SCOPE_LOCAL_CPU ||
+ (preemptible() && !IS_ENABLED(CONFIG_IPIPE)));
return is_midr_in_range_list(read_cpuid_id(), entry->midr_range_list);
}
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index acdef8d76c64d..d65287cc2148b 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2023,7 +2023,8 @@ static void __init mark_const_caps_ready(void)
bool this_cpu_has_cap(unsigned int n)
{
- if (!WARN_ON(preemptible()) && n < ARM64_NCAPS) {
+ if (!WARN_ON(!IS_ENABLED(CONFIG_IPIPE) && preemptible()) &&
+ n < ARM64_NCAPS) {
const struct arm64_cpu_capabilities *cap = cpu_hwcaps_ptrs[n];
if (cap)
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 68c078ab0250c..879ecf0237c88 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -517,9 +517,9 @@ static void erratum_1418040_thread_switch(struct
task_struct *next)
static void erratum_1418040_new_exec(void)
{
- preempt_disable();
+ unsigned long flags = hard_preempt_disable();
erratum_1418040_thread_switch(current);
- preempt_enable();
+ hard_preempt_enable(flags);
}
/*
--
2.34.1
