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BACKPORT: FROMLIST: arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores

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The scheduler now knows enough about these braindead systems to place
32-bit tasks accordingly, so throw out the safety checks and allow the
ret-to-user path to avoid do_notify_resume() if there is nothing to do.

Signed-off-by: Will Deacon <will@kernel.org>
Bug: 178507149
Link: https://lore.kernel.org/linux-arch/20201208132835.6151-16-will@kernel.org/
[will: Fixed trivial conflict with vendor hook in __switch_to()]
Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: I1258f5a95c2c4fc0548103810677b4b0a74320b4
This commit is contained in:
Will Deacon
2020-11-12 21:07:12 +00:00
committed by Will Deacon
parent 7896d24144
commit e4c35a058f
2 changed files with 1 additions and 39 deletions
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14
arch/arm64/kernel/process.c
View File

@@ -538,15 +538,6 @@ static void erratum_1418040_thread_switch(struct task_struct *prev,
write_sysreg(val, cntkctl_el1);
}
static void compat_thread_switch(struct task_struct *next)
{
if (!is_compat_thread(task_thread_info(next)))
return;
if (static_branch_unlikely(&arm64_mismatched_32bit_el0))
set_tsk_thread_flag(next, TIF_NOTIFY_RESUME);
}
/*
* Thread switching.
*/
@@ -563,7 +554,6 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
uao_thread_switch(next);
ssbs_thread_switch(next);
erratum_1418040_thread_switch(prev, next);
compat_thread_switch(next);
/*
* vendor hook is needed before the dsb(),
* because MPAM is related to cache maintenance.
@@ -647,10 +637,8 @@ void arch_setup_new_exec(void)
* at the point of execve(), although we try a bit harder to
* honour the cpuset hierarchy.
*/
if (static_branch_unlikely(&arm64_mismatched_32bit_el0)) {
if (static_branch_unlikely(&arm64_mismatched_32bit_el0))
force_compatible_cpus_allowed_ptr(current);
set_tsk_thread_flag(current, TIF_NOTIFY_RESUME);
}
}
current->mm->context.flags = mmflags;

26
arch/arm64/kernel/signal.c
View File

@@ -911,19 +911,6 @@ static void do_signal(struct pt_regs *regs)
restore_saved_sigmask();
}
static bool cpu_affinity_invalid(struct pt_regs *regs)
{
if (!compat_user_mode(regs))
return false;
/*
* We're preemptible, but a reschedule will cause us to check the
* affinity again.
*/
return !cpumask_test_cpu(raw_smp_processor_id(),
system_32bit_el0_cpumask());
}
asmlinkage void do_notify_resume(struct pt_regs *regs,
unsigned long thread_flags)
{
@@ -954,19 +941,6 @@ asmlinkage void do_notify_resume(struct pt_regs *regs,
if (thread_flags & _TIF_NOTIFY_RESUME) {
tracehook_notify_resume(regs);
rseq_handle_notify_resume(NULL, regs);
/*
* If we reschedule after checking the affinity
* then we must ensure that TIF_NOTIFY_RESUME
* is set so that we check the affinity again.
* Since tracehook_notify_resume() clears the
* flag, ensure that the compiler doesn't move
* it after the affinity check.
*/
barrier();
if (cpu_affinity_invalid(regs))
force_sig(SIGKILL);
}
if (thread_flags & _TIF_FOREIGN_FPSTATE)