Re: [PATCH kvm-unit-tests 8/8] arm/arm64: psci: don't assume method is hvc

From: Andrew Jones <drjones@redhat.com>
To: Nikos Nikoleris <nikos.nikoleris@arm.com>
Cc: kvm@vger.kernel.org, alexandru.elisei@arm.com,
	andre.przywara@arm.com, eric.auger@redhat.com
Subject: Re: [PATCH kvm-unit-tests 8/8] arm/arm64: psci: don't assume method is hvc
Date: Wed, 14 Apr 2021 11:06:47 +0200	[thread overview]
Message-ID: <20210414090647.svahtx74dki3c3vq@kamzik.brq.redhat.com> (raw)
In-Reply-To: <660cfeb4-c411-8335-0351-716a98faf0ae@arm.com>

On Fri, Apr 09, 2021 at 10:46:33AM -0700, Nikos Nikoleris wrote:
> On 07/04/2021 19:59, Andrew Jones wrote:
> > The method can also be smc and it will be when running on bare metal.
> > 
> > Signed-off-by: Andrew Jones <drjones@redhat.com>
> > ---
> >   arm/selftest.c     | 34 +++++++---------------------------
> >   lib/arm/asm/psci.h |  9 +++++++--
> >   lib/arm/psci.c     | 17 +++++++++++++++--
> >   lib/arm/setup.c    | 22 ++++++++++++++++++++++
> >   4 files changed, 51 insertions(+), 31 deletions(-)
> > 
> > diff --git a/arm/selftest.c b/arm/selftest.c
> > index 4495b161cdd5..9f459ed3d571 100644
> > --- a/arm/selftest.c
> > +++ b/arm/selftest.c
> > @@ -400,33 +400,13 @@ static void check_vectors(void *arg __unused)
> >   	exit(report_summary());
> >   }
> > -static bool psci_check(void)
> > +static void psci_print(void)
> >   {
> > -	const struct fdt_property *method;
> > -	int node, len, ver;
> > -
> > -	node = fdt_node_offset_by_compatible(dt_fdt(), -1, "arm,psci-0.2");
> > -	if (node < 0) {
> > -		printf("PSCI v0.2 compatibility required\n");
> > -		return false;
> > -	}
> > -
> > -	method = fdt_get_property(dt_fdt(), node, "method", &len);
> > -	if (method == NULL) {
> > -		printf("bad psci device tree node\n");
> > -		return false;
> > -	}
> > -
> > -	if (len < 4 || strcmp(method->data, "hvc") != 0) {
> > -		printf("psci method must be hvc\n");
> > -		return false;
> > -	}
> > -
> > -	ver = psci_invoke(PSCI_0_2_FN_PSCI_VERSION, 0, 0, 0);
> > -	printf("PSCI version %d.%d\n", PSCI_VERSION_MAJOR(ver),
> > -				       PSCI_VERSION_MINOR(ver));
> > -
> > -	return true;
> > +	int ver = psci_invoke(PSCI_0_2_FN_PSCI_VERSION, 0, 0, 0);
> > +	report_info("PSCI version: %d.%d", PSCI_VERSION_MAJOR(ver),
> > +					  PSCI_VERSION_MINOR(ver));
> > +	report_info("PSCI method: %s", psci_invoke == psci_invoke_hvc ?
> > +				       "hvc" : "smc");
> >   }
> >   static void cpu_report(void *data __unused)
> > @@ -465,7 +445,7 @@ int main(int argc, char **argv)
> >   	} else if (strcmp(argv[1], "smp") == 0) {
> > -		report(psci_check(), "PSCI version");
> > +		psci_print();
> >   		on_cpus(cpu_report, NULL);
> >   		while (!cpumask_full(&ready))
> >   			cpu_relax();
> > diff --git a/lib/arm/asm/psci.h b/lib/arm/asm/psci.h
> > index 7b956bf5987d..e385ce27f5d1 100644
> > --- a/lib/arm/asm/psci.h
> > +++ b/lib/arm/asm/psci.h
> > @@ -3,8 +3,13 @@
> >   #include <libcflat.h>
> >   #include <linux/psci.h>
> > -extern int psci_invoke(unsigned long function_id, unsigned long arg0,
> > -		       unsigned long arg1, unsigned long arg2);
> > +typedef int (*psci_invoke_fn)(unsigned long function_id, unsigned long arg0,
> > +			      unsigned long arg1, unsigned long arg2);
> > +extern psci_invoke_fn psci_invoke;
> > +extern int psci_invoke_hvc(unsigned long function_id, unsigned long arg0,
> > +			   unsigned long arg1, unsigned long arg2);
> > +extern int psci_invoke_smc(unsigned long function_id, unsigned long arg0,
> > +			   unsigned long arg1, unsigned long arg2);
> >   extern int psci_cpu_on(unsigned long cpuid, unsigned long entry_point);
> >   extern void psci_system_reset(void);
> >   extern int cpu_psci_cpu_boot(unsigned int cpu);
> > diff --git a/lib/arm/psci.c b/lib/arm/psci.c
> > index 936c83948b6a..46300f30822c 100644
> > --- a/lib/arm/psci.c
> > +++ b/lib/arm/psci.c
> > @@ -11,9 +11,11 @@
> >   #include <asm/page.h>
> >   #include <asm/smp.h>
> > +psci_invoke_fn psci_invoke;
> > +
> >   __attribute__((noinline))
> > -int psci_invoke(unsigned long function_id, unsigned long arg0,
> > -		unsigned long arg1, unsigned long arg2)
> > +int psci_invoke_hvc(unsigned long function_id, unsigned long arg0,
> > +		    unsigned long arg1, unsigned long arg2)
> >   {
> >   	asm volatile(
> >   		"hvc #0"
> > @@ -22,6 +24,17 @@ int psci_invoke(unsigned long function_id, unsigned long arg0,
> >   	return function_id;
> >   }
> > +__attribute__((noinline))
> 
> Is noinline necessary? We shouldn't be calling psci_invoke_smc and
> psci_invoke_hmc directly, it's unlikely that the compiler will have a chance
> to inline them. But I might be missing something here because I don't see
> why it was there in psci_invoke either.

The noinline ensures that function_id,arg0,arg1,arg2 are in r0-r3 without
us having to do something like

 "mov r0, %0"
 "mov r1, %1"
 "mov r2, %2"
 "mov r3, %3"

in the asm().

> 
> Otherwise Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>

Thanks!
drew