Re: [kvm-unit-tests PATCH 11/14] powerpc/ppc64: add rtas_power_off

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On Tue, Aug 04, 2015 at 02:03:24PM +1000, David Gibson wrote:
> On Mon, Aug 03, 2015 at 04:41:28PM +0200, Andrew Jones wrote:
> > Add enough RTAS support to support power-off, and apply it to
> > exit().
> > 
> > Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
> > ---
> >  lib/powerpc/asm/rtas.h  | 27 ++++++++++++++++
> >  lib/powerpc/io.c        |  3 ++
> >  lib/powerpc/rtas.c      | 84 +++++++++++++++++++++++++++++++++++++++++++++++++
> >  lib/ppc64/asm/rtas.h    |  1 +
> >  powerpc/Makefile.common |  1 +
> >  powerpc/cstart64.S      |  9 ++++++
> >  6 files changed, 125 insertions(+)
> >  create mode 100644 lib/powerpc/asm/rtas.h
> >  create mode 100644 lib/powerpc/rtas.c
> >  create mode 100644 lib/ppc64/asm/rtas.h
> > 
> > diff --git a/lib/powerpc/asm/rtas.h b/lib/powerpc/asm/rtas.h
> > new file mode 100644
> > index 0000000000000..53ce126c69a42
> > --- /dev/null
> > +++ b/lib/powerpc/asm/rtas.h
> > @@ -0,0 +1,27 @@
> > +#ifndef _ASMPOWERPC_RTAS_H_
> > +#define _ASMPOWERPC_RTAS_H_
> > +/*
> > + * Copyright (C) 2015, Red Hat Inc, Andrew Jones <drjones@xxxxxxxxxx>
> > + *
> > + * This work is licensed under the terms of the GNU LGPL, version 2.
> > + */
> > +#include <libcflat.h>
> > +
> > +#define RTAS_UNKNOWN_SERVICE	(-1)
> > +
> > +struct rtas_args {
> > +	u32 token;
> > +	u32 nargs;
> > +	u32 nret;
> > +	u32 args[16];
> > +	u32 *rets;
> > +};
> > +
> > +extern void rtas_init(void);
> > +extern void enter_rtas(unsigned long args);
> > +extern int rtas_token(const char *service);
> > +extern int rtas_call(int token, int nargs, int nret, int *outputs, ...);
> > +
> > +extern void rtas_power_off(void);
> > +
> > +#endif /* _ASMPOWERPC_RTAS_H_ */
> > diff --git a/lib/powerpc/io.c b/lib/powerpc/io.c
> > index a7eaafeca9205..25cdd0ad961ee 100644
> > --- a/lib/powerpc/io.c
> > +++ b/lib/powerpc/io.c
> > @@ -7,6 +7,7 @@
> >   */
> >  #include <libcflat.h>
> >  #include <asm/spinlock.h>
> > +#include <asm/rtas.h>
> >  
> >  extern void halt(int code);
> >  extern void putchar(int c);
> > @@ -15,6 +16,7 @@ static struct spinlock uart_lock;
> >  
> >  void io_init(void)
> >  {
> > +	rtas_init();
> >  }
> >  
> >  void puts(const char *s)
> > @@ -27,5 +29,6 @@ void puts(const char *s)
> >  
> >  void exit(int code)
> >  {
> > +	rtas_power_off();
> >  	halt(code);
> >  }
> > diff --git a/lib/powerpc/rtas.c b/lib/powerpc/rtas.c
> > new file mode 100644
> > index 0000000000000..39f7d4428ee77
> > --- /dev/null
> > +++ b/lib/powerpc/rtas.c
> > @@ -0,0 +1,84 @@
> > +/*
> > + * powerpc RTAS
> > + *
> > + * Copyright (C) 2015, Red Hat Inc, Andrew Jones <drjones@xxxxxxxxxx>
> > + *
> > + * This work is licensed under the terms of the GNU LGPL, version 2.
> > + */
> > +#include <libcflat.h>
> > +#include <libfdt/libfdt.h>
> > +#include <devicetree.h>
> > +#include <asm/spinlock.h>
> > +#include <asm/io.h>
> > +#include <asm/rtas.h>
> > +
> > +static struct spinlock lock;
> > +struct rtas_args rtas_args;
> > +static int rtas_node;
> > +
> > +void rtas_init(void)
> > +{
> > +	if (!dt_available()) {
> > +		printf("%s: No device tree!\n", __func__);
> > +		abort();
> > +	}
> > +
> > +	rtas_node = fdt_path_offset(dt_fdt(), "/rtas");
> > +	if (rtas_node < 0) {
> > +		printf("%s: /rtas node: %s\n", __func__,
> > +			fdt_strerror(rtas_node));
> > +		abort();
> > +	}
> > +}
> > +
> > +int rtas_token(const char *service)
> > +{
> > +	const struct fdt_property *prop;
> > +	u32 *token;
> > +
> > +	prop = fdt_get_property(dt_fdt(), rtas_node, service, NULL);
> > +	if (prop) {
> > +		token = (u32 *)prop->data;
> > +		return fdt32_to_cpu(*token);
> > +	}
> > +	return RTAS_UNKNOWN_SERVICE;
> > +}
> > +
> > +int rtas_call(int token, int nargs, int nret, int *outputs, ...)
> > +{
> > +	va_list list;
> > +	int ret, i;
> > +
> > +	spin_lock(&lock);
> > +
> > +	rtas_args.token = cpu_to_be32(token);
> > +	rtas_args.nargs = cpu_to_be32(nargs);
> > +	rtas_args.nret = cpu_to_be32(nret);
> > +	rtas_args.rets = &rtas_args.args[nargs];
> > +
> > +	va_start(list, outputs);
> > +	for (i = 0; i < nargs; ++i)
> > +		rtas_args.args[i] = cpu_to_be32(va_arg(list, u32));
> > +	va_end(list);
> > +
> > +	for (i = 0; i < nret; ++i)
> > +		rtas_args.rets[i] = 0;
> > +
> > +	enter_rtas(__pa(&rtas_args));
> > +
> > +	if (nret > 1 && outputs != NULL)
> > +		for (i = 0; i < nret - 1; ++i)
> > +			outputs[i] = be32_to_cpu(rtas_args.rets[i + 1]);
> > +
> > +	ret = nret > 0 ? be32_to_cpu(rtas_args.rets[0]) : 0;
> > +
> > +	spin_unlock(&lock);
> > +	return ret;
> > +}
> > +
> > +void rtas_power_off(void)
> > +{
> > +	printf("RTAS power-off returned %d\n",
> > +		rtas_call(rtas_token("power-off"), 2, 1, NULL, -1, -1));
> > +	assert(0);
> > +}
> > diff --git a/lib/ppc64/asm/rtas.h b/lib/ppc64/asm/rtas.h
> > new file mode 100644
> > index 0000000000000..fe77f635cd860
> > --- /dev/null
> > +++ b/lib/ppc64/asm/rtas.h
> > @@ -0,0 +1 @@
> > +#include "../../powerpc/asm/rtas.h"
> > diff --git a/powerpc/Makefile.common b/powerpc/Makefile.common
> > index b130342dee60e..f4eff7f8eccb4 100644
> > --- a/powerpc/Makefile.common
> > +++ b/powerpc/Makefile.common
> > @@ -39,6 +39,7 @@ cflatobjs += lib/powerpc/io.o
> >  cflatobjs += lib/powerpc/setup.o
> >  cflatobjs += lib/powerpc/mmu.o
> >  cflatobjs += lib/powerpc/smp.o
> > +cflatobjs += lib/powerpc/rtas.o
> >  
> >  libgcc := $(shell $(CC) $(machine) --print-libgcc-file-name)
> >  start_addr := $(shell printf "%x\n" $$(( $(phys_base) + $(kernel_offset) )))
> > diff --git a/powerpc/cstart64.S b/powerpc/cstart64.S
> > index 8edaaa6e251fc..1c48083efa33c 100644
> > --- a/powerpc/cstart64.S
> > +++ b/powerpc/cstart64.S
> > @@ -8,6 +8,7 @@
> >  
> >  #define HVSC			.long 0x44000022
> >  #define H_PUT_TERM_CHAR		0x58
> > +#define KVMPPC_H_RTAS		0xf000
> >  
> >  #define LOAD_REG_IMMEDIATE(reg,expr)		\
> >  	lis	reg,(expr)@highest;		\
> > @@ -85,3 +86,11 @@ putchar:
> >  	li	r5, 1	/* sending just 1 byte */
> >  	HVSC
> >  	blr
> > +
> > +.globl enter_rtas
> > +enter_rtas:
> > +	mr	r4, r3
> > +	lis	r3, KVMPPC_H_RTAS@h
> > +	ori	r3, r3, KVMPPC_H_RTAS@l
> > +	HVSC
> > +	blr
> 
> So, strictly speaking this isn't how a client program is supposed to
> access RTAS.  Instead, you're supposed to call into SLOF to
> instantiate RTAS, then jump into the blob it gives you.  Or, if you're
> replacing rather than using SLOF, then you're supposed to get the
> existing RTAS blob address from the device tree and jump into that (or
> copy it somewhere else yourself).
> 
> In practice that RTAS blob will have the same 5 instructions as your
> enter_rtas, so it's probably ok to do this.
> 
> What concerns me slightly, though, is that if we ever messed up the
> RTAS blob handling in qemu or SLOF, then bypassing it in the kvm tests
> like this means they wouldn't catch that breakage.

I'll look into doing this properly. It doesn't sound like it'd be much
effort.

Thanks,
drew

> 
> -- 
> David Gibson			| I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
> 				| _way_ _around_!
> http://www.ozlabs.org/~dgibson


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