On Tue, 12 Jan 2021 at 19:09, Stefano Stabellini <sstabell...@kernel.org> wrote: > > On Tue, 12 Jan 2021, Julien Grall wrote: > > > + aarch32 = c->pfr64.el1 == 2; > > > > This is checking that AArch32 is available in EL1. However, it may not be > > the > > case yet it would be available in EL0. > > > > As a consequence, 32-bit userspace wouldn't work properly after this patch. > > > > The Arm Arm mandates that if AArch32 is available at EL(n), then it must be > > available at EL(n - 1). > > > > So we should check that AArch32 is available at EL0 because this would > > cover the case where AArch32 is enabled at EL1. > > OK > > > > Furthermore, I would also like to avoid hardcoding value in the code as it > > is > > less readable. We already define cpu_has_el0_32 which use the boot CPU > > feature. Maybe we want to expand the macro or split it? > > I agree > > Technically, cpu_has_el0_32 works as is, because it is called after > boot_cpu_data has been updated. So we could just use it. What do you > think?
I thought about that when I wrote the first e-mail. However, this would not work properly for heterogeneous platforms. There is still a risk to read garbage (or UNDEF) if the boot CPU supports AArch32 but the others. Cheers,
