On Fri, Nov 27, 2020 at 01:17:59PM +0000, Qais Yousef wrote: > On 11/24/20 15:50, Will Deacon wrote: > > Allow systems with mismatched 32-bit support at EL0 to run 32-bit > > applications based on a new kernel parameter. > > > > Signed-off-by: Will Deacon <will@xxxxxxxxxx> > > --- > > Documentation/admin-guide/kernel-parameters.txt | 7 +++++++ > > arch/arm64/kernel/cpufeature.c | 7 +++++++ > > 2 files changed, 14 insertions(+) > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > > index 526d65d8573a..f20188c44d83 100644 > > --- a/Documentation/admin-guide/kernel-parameters.txt > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > @@ -289,6 +289,13 @@ > > do not want to use tracing_snapshot_alloc() as it needs > > to be done where GFP_KERNEL allocations are allowed. > > > > + allow_mismatched_32bit_el0 [ARM64] > > + Allow execve() of 32-bit applications and setting of the > > + PER_LINUX32 personality on systems where only a strict > > + subset of the CPUs support 32-bit EL0. When this > > + parameter is present, the set of CPUs supporting 32-bit > > + EL0 is indicated by /sys/devices/system/cpu/aarch32_el0. > > Shouldn't we document that a randomly selected 32-bit CPU will be prevented > from being hotplugged out all the time to act as the last man standing for any > currently running 32-bit application. > > That was a mouthful! I'm sure you can phrase it better :-) Sure, I'll have a go at adding something. Thanks. > If we make this the last patch as it was before adding affinity handling, we > can drop patch 4 more easily I think? I'd still prefer to keep patch 4, but I can certainly try to move this one later in the series. Will
