Re: [kvm-unit-tests PATCH v2 13/14] powerpc/ppc64: add RTAS support

[Thomas Huth <thuth@redhat.com>]

On 08.02.2016 19:53, 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>
> ---
>  lib/powerpc/asm/rtas.h  |  26 +++++++++++
>  lib/powerpc/io.c        |   2 +
>  lib/powerpc/rtas.c      | 120 ++++++++++++++++++++++++++++++++++++++++++++++++
>  lib/ppc64/asm/rtas.h    |   1 +
>  powerpc/Makefile.common |   1 +
>  5 files changed, 150 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/rtas.c b/lib/powerpc/rtas.c
> new file mode 100644
> index 0000000000000..7fcd667513087
> --- /dev/null
> +++ b/lib/powerpc/rtas.c
> @@ -0,0 +1,120 @@
> +/*
> + * 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/io.h>
> +#include <asm/rtas.h>
> +
> +#if defined(__powerpc64__)
> +struct func_ptr {
> +	unsigned long ptr;
> +	unsigned long toc;

Theoretically, there should be a third value "env" or so here (see
<http://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi.html#FUNC-DES>),
but for C-code it likely does not matter.

> +};
> +static struct func_ptr rtas_entry_funcptr;
> +#endif
> +typedef void (*rtas_entry_t)(unsigned long);
> +static rtas_entry_t enter_rtas;
> +static struct rtas_args rtas_args;
> +static struct spinlock 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)
> +{
> +	const struct fdt_property *prop;
> +	unsigned long entry;
> +	u32 *data;
> +	int len;
> +
> +	if (!dt_available()) {
> +		printf("%s: No device tree!\n", __func__);
> +		abort();
> +	}
> +
> +	prop = fdt_get_property(dt_fdt(), rtas_node(),
> +				"linux,rtas-entry", &len);
> +	if (!prop) {
> +		printf("%s: /rtas/linux,rtas-entry: %s\n",
> +				__func__, fdt_strerror(len));
> +		abort();
> +	}
> +
> +	data = (u32 *)prop->data;
> +	entry = (unsigned long)fdt32_to_cpu(*data);
> +
> +#if defined(__powerpc64__)
> +	rtas_entry_funcptr.ptr = entry;
> +	enter_rtas = (rtas_entry_t)&rtas_entry_funcptr;
> +#else
> +	enter_rtas = (rtas_entry_t)entry;
> +#endif
> +}
> +
> +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);
> +}

As discussed in IRC already, that assert() can cause an endless loop...
but apart from that, the patch looks fine to me.

 Thomas