On Tuesday 24 Nov 2020 at 15:50:33 (+0000), Will Deacon wrote: > When exec'ing a 32-bit task on a system with mismatched support for > 32-bit EL0, try to ensure that it starts life on a CPU that can actually > run it. > > Signed-off-by: Will Deacon <[email protected]> > --- > arch/arm64/kernel/process.c | 42 ++++++++++++++++++++++++++++++++++++- > 1 file changed, 41 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > index 1540ab0fbf23..72116b0c7c73 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -31,6 +31,7 @@ > #include <linux/interrupt.h> > #include <linux/init.h> > #include <linux/cpu.h> > +#include <linux/cpuset.h> > #include <linux/elfcore.h> > #include <linux/pm.h> > #include <linux/tick.h> > @@ -625,6 +626,45 @@ unsigned long arch_align_stack(unsigned long sp) > return sp & ~0xf; > } > > +static void adjust_compat_task_affinity(struct task_struct *p) > +{ > + cpumask_var_t cpuset_mask; > + const struct cpumask *possible_mask = system_32bit_el0_cpumask(); > + const struct cpumask *newmask = possible_mask; > + > + /* > + * Restrict the CPU affinity mask for a 32-bit task so that it contains > + * only the 32-bit-capable subset of its original CPU mask. If this is > + * empty, then try again with the cpuset allowed mask. If that fails, > + * forcefully override it with the set of all 32-bit-capable CPUs that > + * we know about. > + * > + * From the perspective of the task, this looks similar to what would > + * happen if the 64-bit-only CPUs were hot-unplugged at the point of > + * execve(). > + */ > + if (!restrict_cpus_allowed_ptr(p, possible_mask)) > + goto out; > + > + if (alloc_cpumask_var(&cpuset_mask, GFP_KERNEL)) { > + cpuset_cpus_allowed(p, cpuset_mask); > + if (cpumask_and(cpuset_mask, cpuset_mask, possible_mask)) { > + newmask = cpuset_mask; > + goto out_set_mask; > + } > + } > + > + if (printk_ratelimit()) { > + printk_deferred("Overriding affinity for 32-bit process %d (%s) > to CPUs %*pbl\n", > + task_pid_nr(p), p->comm, > cpumask_pr_args(newmask)); > + } > +out_set_mask: > + set_cpus_allowed_ptr(p, newmask); > + free_cpumask_var(cpuset_mask); > +out: > + set_tsk_thread_flag(current, TIF_NOTIFY_RESUME); > +}
This starts to look an awful lot like select_fallback_rq(), but I suppose we shouldn't bother factoring out that code yet as we probably don't want this pattern to be re-used all over, so: Reviewed-by: Quentin Perret <[email protected]> Thanks, Quentin
