[PATCH 4/4] efi_loader: call smp_kick_all_cpus()

[Tom Rini <trini@konsulko.com>]

On Sat, May 16, 2020 at 05:54:43PM +0200, Michael Walle wrote:
> [Also adding Tom Rini as ARM maintainer]
> 
> Am 2020-05-14 22:17, schrieb Alexander Graf:
> > On 14.05.20 20:46, Heinrich Schuchardt wrote:
> > > On 5/14/20 2:38 PM, Michael Walle wrote:
> > > > On some architectures, specifically the layerscape, the
> > > > secondary cores
> > > > wait for an interrupt before entering the spin-tables. This
> > > > applies only
> > > > to boards which doesn't have PSCI provided by TF-a and u-boot
> > > > does the
> > > %s/TF-a/TF-A/, %s/u-boot/U-Boot/
> > > 
> > > > secondary cores handling.
> > > > bootm/booti already call that function for ARM architecture;
> > > > also add it
> > > > to bootelf before switching to EL2. Additionally, provide a weak noop
> > > > function so we don't have to have "#ifdef CONFIG_ARM64" guards.
> > > > 
> > > > Signed-off-by: Michael Walle <michael@walle.cc>
> > > > ---
> > > >   common/bootm.c             | 9 +++++++++
> > > >   lib/efi_loader/efi_setup.c | 6 ++++++
> > > >   2 files changed, 15 insertions(+)
> > > > 
> > > > diff --git a/common/bootm.c b/common/bootm.c
> > > > index db4362a643..65adf29329 100644
> > > > --- a/common/bootm.c
> > > > +++ b/common/bootm.c
> > > > @@ -816,6 +816,15 @@ void __weak switch_to_non_secure_mode(void)
> > > >   {
> > > >   }
> > > > 
> > > > +/**
> > > > + * smp_kick_all_cpus() - kick all CPUs
> > > > + *
> > > > + * This routine is overridden by architectures requiring this
> > > > feature.
> > > > + */
> > > > +void __weak smp_kick_all_cpus(void)
> > > > +{
> > > > +}
> > > > +
> > > >   #else /* USE_HOSTCC */
> > > > 
> > > >   #if defined(CONFIG_FIT_SIGNATURE)
> > > > diff --git a/lib/efi_loader/efi_setup.c b/lib/efi_loader/efi_setup.c
> > > > index 26a7423203..7e5364adc5 100644
> > > > --- a/lib/efi_loader/efi_setup.c
> > > > +++ b/lib/efi_loader/efi_setup.c
> > > > @@ -132,6 +132,12 @@ efi_status_t efi_init_obj_list(void)
> > > >   	/* Allow unaligned memory access */
> > > >   	allow_unaligned();
> > > > 
> > > > +	/*
> > > > +	 * Some architectures need to kick secondary cores to enter their
> > > > +	 * spin table.
> > > > +	 */
> > > > +	smp_kick_all_cpus();
> > > This will not compile with
> > > 
> > > CONFIG_CMD_BOOTI=n
> > > CONFIG_CMD_BOOTM=n
> > > CONFIG_CMD_BOOTZ=n
> > 
> > 
> > Much worse is that in incurs needless overhead on PSCI capable
> > platforms. Can we move the smp_kick_all_cpus() to the board or soc
> > level of the few systems that use spin tables please? :)
> 
> Ok, I'm not sure where I should put the smp_kick_all_cpus(). In the
> bootm/booti path this is done in boot_jump_linux() (unconditionally
> in do_nonsec_virt_switch()). Therefore, shouldn't the kick be in
> switch_to_non_secure_mode(), too?
> 
> Regarding the overhead, isn't it just called once before starting
> the OS? Is that really worth adding yet another weak function or
> ifdef guards? Isn't it better to behave like the bootm case?

So, I think this shows that there's some consolidation needed as VxWorks
and ELF support have also had to solve this problem and are copying
around the same code that I believe Alex is saying we should in fact not
need on SoCs that handle this via PSCI instead of a spintable?

-- 
Tom
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