On Fri, 12 Mar 2021 at 11:20, Andrew Scull <ascull@xxxxxxxxxx> wrote:
>
> On Thu, 11 Mar 2021 at 10:35, Quentin Perret <qperret@xxxxxxxxxx> wrote:
> >
> > On Thursday 04 Mar 2021 at 11:54:47 (+0000), 'Andrew Scull' via kernel-team wrote:
> > > smp_procesor_id() works off of the cpu_number per-cpu variable. Create
> > > an nVHE hyp version of cpu_number and initialize it to the same value as
> > > the host when creating the hyp per-cpu regions.
> > >
> > > Signed-off-by: Andrew Scull <ascull@xxxxxxxxxx>
> > > ---
> > > arch/arm64/kvm/arm.c | 2 ++
> > > arch/arm64/kvm/hyp/nvhe/hyp-smp.c | 2 ++
> > > 2 files changed, 4 insertions(+)
> > >
> > > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> > > index 26ccc369cf11..e3edea8379f3 100644
> > > --- a/arch/arm64/kvm/arm.c
> > > +++ b/arch/arm64/kvm/arm.c
> > > @@ -54,6 +54,7 @@ DECLARE_KVM_HYP_PER_CPU(unsigned long, kvm_hyp_vector);
> > > static DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_page);
> > > unsigned long kvm_arm_hyp_percpu_base[NR_CPUS];
> > > DECLARE_KVM_NVHE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);
> > > +DECLARE_KVM_NVHE_PER_CPU(int, cpu_number);
> > >
> > > /* The VMID used in the VTTBR */
> > > static atomic64_t kvm_vmid_gen = ATOMIC64_INIT(1);
> > > @@ -1740,6 +1741,7 @@ static int init_hyp_mode(void)
> > > page_addr = page_address(page);
> > > memcpy(page_addr, CHOOSE_NVHE_SYM(__per_cpu_start), nvhe_percpu_size());
> > > kvm_arm_hyp_percpu_base[cpu] = (unsigned long)page_addr;
> > > + *per_cpu_ptr_nvhe_sym(cpu_number, cpu) = cpu;
> > > }
> > >
> > > /*
> > > diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-smp.c b/arch/arm64/kvm/hyp/nvhe/hyp-smp.c
> > > index 879559057dee..86f952b1de18 100644
> > > --- a/arch/arm64/kvm/hyp/nvhe/hyp-smp.c
> > > +++ b/arch/arm64/kvm/hyp/nvhe/hyp-smp.c
> > > @@ -8,6 +8,8 @@
> > > #include <asm/kvm_hyp.h>
> > > #include <asm/kvm_mmu.h>
> > >
> > > +DEFINE_PER_CPU_READ_MOSTLY(int, cpu_number);
> >
> > Is smp_processor_id() going to work at EL2 with CONFIG_DEBUG_PREEMPT=y ?
> > If not, then maybe we should have out own hyp_smp_processor_id() macro?
>
> It's not, preempt_count() won't work,= at a minimum. I got far too
> drawn into the other branch of that #ifdef.
>
> We only use __smp_processor_id() in hyp, but that might not play too
> nicely with VHE and forgetting the leading underscores will just lead
> to nVHE issues that might not be caught in the build.
>
> So you might be right that this is a case where we need to break from
> standard APIs. And we can define `raw_smp_processor_id()` to something
> that will give a compile time error when used in hyp to try and
> prevent accidental misuse.
Having just read the build error again:
:236: undefined reference to `__kvm_nvhe_debug_smp_processor_id'
Another option could be to define `debug_smp_processor_id()` for nvhe,
which is easy since preemption is always disabled, IIRC.
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