Re: [kvm-unit-tests PATCH v6 17/18] powerpc/ppc64: add RTAS support

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Feb 23, 2016 at 04:03:55PM +0100, Andrew Jones wrote:
> On Mon, Feb 22, 2016 at 02:26:28PM +1100, David Gibson wrote:
> > On Fri, Feb 19, 2016 at 04:58:22PM +0100, Andrew Jones wrote:
> > > Add enough RTAS support to start adding RTAS commands. Just add
> > > power-off for now.
> > > 
> > > Signed-off-by: Andrew Jones <drjones@redhat.com>
> > > Reviewed-by: Thomas Huth <thuth@redhat.com>
> > > Tested-by: Laurent Vivier <lvivier@redhat.com>
> > > Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> > > ---
> > >  lib/powerpc/asm/rtas.h  |  26 +++++++++
> > >  lib/powerpc/io.c        |   2 +
> > >  lib/powerpc/rtas.c      | 139 ++++++++++++++++++++++++++++++++++++++++++++++++
> > >  lib/ppc64/asm/rtas.h    |   1 +
> > >  powerpc/Makefile.common |   1 +
> > >  5 files changed, 169 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..522225bcb6de3
> > > --- /dev/null
> > > +++ b/lib/powerpc/asm/rtas.h
> > > @@ -0,0 +1,26 @@
> > > +#ifndef _ASMPOWERPC_RTAS_H_
> > > +#define _ASMPOWERPC_RTAS_H_
> > > +/*
> > > + * Copyright (C) 2016, Red Hat Inc, Andrew Jones <drjones@redhat.com>
> > > + *
> > > + * 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 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 ef90946fb1131..c4c61ea8ac1cf 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 print_lock;
> > >  
> > >  void io_init(void)
> > >  {
> > > +	rtas_init();
> > >  }
> > >  
> > >  void puts(const char *s)
> > > diff --git a/lib/powerpc/rtas.c b/lib/powerpc/rtas.c
> > > new file mode 100644
> > > index 0000000000000..464d066d3c220
> > > --- /dev/null
> > > +++ b/lib/powerpc/rtas.c
> > > @@ -0,0 +1,139 @@
> > > +/*
> > > + * powerpc RTAS
> > > + *
> > > + * Copyright (C) 2016, Red Hat Inc, Andrew Jones <drjones@redhat.com>
> > > + *
> > > + * 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/hcall.h>
> > > +#include <asm/io.h>
> > > +#include <asm/rtas.h>
> > > +
> > > +#define RTAS_BLOB_WORDS 8
> > > +
> > > +#if defined(__powerpc64__)
> > > +struct func_ptr {
> > > +	unsigned long ptr;
> > > +	unsigned long toc;
> > > +};
> > > +static struct func_ptr rtas_entry_funcptr;
> > > +#endif
> > > +static u32 rtas_blob[RTAS_BLOB_WORDS];
> > > +typedef void (*rtas_entry_t)(unsigned long);
> > > +static rtas_entry_t enter_rtas;
> > > +static struct rtas_args rtas_args;
> > > +static struct spinlock rtas_lock;
> > > +
> > > +static int rtas_node(void)
> > > +{
> > > +	int node = fdt_path_offset(dt_fdt(), "/rtas");
> > > +
> > > +	if (node < 0) {
> > > +		printf("%s: /rtas: %s\n", __func__, fdt_strerror(node));
> > > +		abort();
> > > +	}
> > > +
> > > +	return node;
> > > +}
> > > +
> > > +void rtas_init(void)
> > > +{
> > > +	bool broken_sc1 = hcall_have_broken_sc1();
> > > +	int node = rtas_node(), len, words, i;
> > > +	const struct fdt_property *prop;
> > > +	u32 *data, *insns;
> > > +
> > > +	if (!dt_available()) {
> > > +		printf("%s: No device tree!\n", __func__);
> > > +		abort();
> > > +	}
> > > +
> > > +	prop = fdt_get_property(dt_fdt(), node,
> > > +				"linux,rtas-entry", &len);
> > > +	if (!prop) {
> > > +		printf("%s: /rtas/linux,rtas-entry: %s\n",
> > > +				__func__, fdt_strerror(len));
> > > +		abort();
> > > +	}
> > > +
> > > +	data = (u32 *)prop->data;
> > > +	insns = (u32 *)(unsigned long)fdt32_to_cpu(*data);
> > > +
> > > +	prop = fdt_get_property(dt_fdt(), node, "rtas-size", &len);
> > > +	if (!prop) {
> > > +		printf("%s: /rtas/rtas-size: %s\n",
> > > +				__func__, fdt_strerror(len));
> > > +		abort();
> > > +	}
> > > +	data = (u32 *)prop->data;
> > > +	words = (int)fdt32_to_cpu(*data)/4;
> > > +	assert(words <= RTAS_BLOB_WORDS);
> > > +
> > > +	for (i = 0; i < words; ++i) {
> > > +		rtas_blob[i] = be32_to_cpu(insns[i]);
> > > +		if (broken_sc1 && rtas_blob[i] == SC1)
> > > +			rtas_blob[i] = SC1_REPLACEMENT;
> > > +	}
> > 
> > Hmm.. in general it's not guaranteed that you can copy around the RTAS
> > blob and have it still work.  But.. you're working essentially at the
> > same level as SLOF here, rather than a "normal" OS and I think SLOF
> > must make the same assumption.  So I guess it's ok.
> 
> I can edit the instructions in place, like I was doing before, as now...

I don't think it really matters.

> > 
> > > +#if defined(__powerpc64__)
> > 
> > Technically this ifdef should be based on the ABI version, rather than
> > __powerpc64__, but I'm not sure if there are standard #defines for that.
> > 
> > > +	rtas_entry_funcptr.ptr = (unsigned long)rtas_blob;
> > > +	enter_rtas = (rtas_entry_t)&rtas_entry_funcptr;
> > > +#else
> > > +	enter_rtas = (rtas_entry_t)rtas_blob;
> > > +#endif
> > 
> > I think you may want to have an actual coded enter_rtas function,
> > rather than just constructing a function pointer around the raw blob.
> > For one thing it should reduce the ugly ABI version #ifdefs.  More
> > importantly though, you can use it to set up the correct MSR state for
> > entry into RTAS (IR, DR, EE off, big-endian, ..).  At the moment all
> > your code runs in a suitable MSR state to call directly into RTAS, but
> > that will probably change fairly soon.
> 
> ...I see I don't need to edit all instructions wrt to endianness. The
> "call RTAS with BE state", even if running LE, was something I had
> missed, which means the above code (converting the BE blob to cpu
> endian) was the wrong thing to do. I've now added an assembler enter_rtas
> function, which doesn't do anything special yet, but I think I know what
> needs to be done with it, at least for LE enablement.

Right.  The RTAS blob needs to be entered in BE mode, and technically
in 32-bit mode as well, although the one we use in KVM will work fine
in 64-bit mode as well.  That does also mean it can technically
clobber the upper halves of a lot of registers - see the kernel
enter_rtas().

-- 
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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