Re: [PATCH v2 6/9] powerpc/microwatt: Add support for hardware random number generator
Excerpts from Segher Boessenkool's message of June 20, 2021 12:36 am: > On Sat, Jun 19, 2021 at 01:08:51PM +1000, Nicholas Piggin wrote: >> Excerpts from Paul Mackerras's message of June 18, 2021 1:47 pm: >> > Microwatt's hardware RNG is accessed using the DARN instruction. >> >> I think we're getting a platforms/book3s soon with the VAS patches, >> might be a place to add the get_random_darn function. >> >> Huh, DARN is unprivileged right? > > It is, that's the whole point: to make it very very cheap for user > software it has to be an unprivileged instruction. Right, I was just doing a double-take. In that case we should enable it in the pseries random number code as well, so it really would be a generic isa 3.0 function that all (microwatt, powernv, pseries) could use AFAIKS. Thanks, Nick
Re: [PATCH v2 6/9] powerpc/microwatt: Add support for hardware random number generator
On Sat, Jun 19, 2021 at 01:08:51PM +1000, Nicholas Piggin wrote: > Excerpts from Paul Mackerras's message of June 18, 2021 1:47 pm: > > Microwatt's hardware RNG is accessed using the DARN instruction. > > I think we're getting a platforms/book3s soon with the VAS patches, > might be a place to add the get_random_darn function. > > Huh, DARN is unprivileged right? It is, that's the whole point: to make it very very cheap for user software it has to be an unprivileged instruction. Segher
Re: [PATCH v2 6/9] powerpc/microwatt: Add support for hardware random number generator
Excerpts from Paul Mackerras's message of June 18, 2021 1:47 pm:
> Microwatt's hardware RNG is accessed using the DARN instruction.
>
I think we're getting a platforms/book3s soon with the VAS patches,
might be a place to add the get_random_darn function.
Huh, DARN is unprivileged right? And yet we haven't wired it up in
pseries it still uses an hcall.
Anyway that's all stuff to sort out later.
Reviewed-by: Nicholas Piggin
> Signed-off-by: Paul Mackerras
> ---
> arch/powerpc/platforms/microwatt/Kconfig | 1 +
> arch/powerpc/platforms/microwatt/Makefile | 2 +-
> arch/powerpc/platforms/microwatt/rng.c| 48 +++
> 3 files changed, 50 insertions(+), 1 deletion(-)
> create mode 100644 arch/powerpc/platforms/microwatt/rng.c
>
> diff --git a/arch/powerpc/platforms/microwatt/Kconfig
> b/arch/powerpc/platforms/microwatt/Kconfig
> index 50ed0cedb5f1..8f6a81978461 100644
> --- a/arch/powerpc/platforms/microwatt/Kconfig
> +++ b/arch/powerpc/platforms/microwatt/Kconfig
> @@ -7,6 +7,7 @@ config PPC_MICROWATT
> select PPC_ICP_NATIVE
> select PPC_NATIVE
> select PPC_UDBG_16550
> + select ARCH_RANDOM
> help
>This option enables support for FPGA-based Microwatt
> implementations.
>
> diff --git a/arch/powerpc/platforms/microwatt/Makefile
> b/arch/powerpc/platforms/microwatt/Makefile
> index e6885b3b2ee7..116d6d3ad3f0 100644
> --- a/arch/powerpc/platforms/microwatt/Makefile
> +++ b/arch/powerpc/platforms/microwatt/Makefile
> @@ -1 +1 @@
> -obj-y+= setup.o
> +obj-y+= setup.o rng.o
> diff --git a/arch/powerpc/platforms/microwatt/rng.c
> b/arch/powerpc/platforms/microwatt/rng.c
> new file mode 100644
> index ..3d8ee6eb7dad
> --- /dev/null
> +++ b/arch/powerpc/platforms/microwatt/rng.c
> @@ -0,0 +1,48 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Derived from arch/powerpc/platforms/powernv/rng.c, which is:
> + * Copyright 2013, Michael Ellerman, IBM Corporation.
> + */
> +
> +#define pr_fmt(fmt) "microwatt-rng: " fmt
> +
> +#include
> +#include
> +#include
> +#include
> +#include
> +
> +#define DARN_ERR 0xul
> +
> +int microwatt_get_random_darn(unsigned long *v)
> +{
> + unsigned long val;
> +
> + /* Using DARN with L=1 - 64-bit conditioned random number */
> + asm volatile(PPC_DARN(%0, 1) : "=r"(val));
> +
> + if (val == DARN_ERR)
> + return 0;
> +
> + *v = val;
> +
> + return 1;
> +}
> +
> +static __init int rng_init(void)
> +{
> + unsigned long val;
> + int i;
> +
> + for (i = 0; i < 10; i++) {
> + if (microwatt_get_random_darn()) {
> + ppc_md.get_random_seed = microwatt_get_random_darn;
> + return 0;
> + }
> + }
> +
> + pr_warn("Unable to use DARN for get_random_seed()\n");
> +
> + return -EIO;
> +}
> +machine_subsys_initcall(, rng_init);
> --
> 2.31.1
>
>
[PATCH v2 6/9] powerpc/microwatt: Add support for hardware random number generator
Microwatt's hardware RNG is accessed using the DARN instruction.
Signed-off-by: Paul Mackerras
---
arch/powerpc/platforms/microwatt/Kconfig | 1 +
arch/powerpc/platforms/microwatt/Makefile | 2 +-
arch/powerpc/platforms/microwatt/rng.c| 48 +++
3 files changed, 50 insertions(+), 1 deletion(-)
create mode 100644 arch/powerpc/platforms/microwatt/rng.c
diff --git a/arch/powerpc/platforms/microwatt/Kconfig
b/arch/powerpc/platforms/microwatt/Kconfig
index 50ed0cedb5f1..8f6a81978461 100644
--- a/arch/powerpc/platforms/microwatt/Kconfig
+++ b/arch/powerpc/platforms/microwatt/Kconfig
@@ -7,6 +7,7 @@ config PPC_MICROWATT
select PPC_ICP_NATIVE
select PPC_NATIVE
select PPC_UDBG_16550
+ select ARCH_RANDOM
help
This option enables support for FPGA-based Microwatt implementations.
diff --git a/arch/powerpc/platforms/microwatt/Makefile
b/arch/powerpc/platforms/microwatt/Makefile
index e6885b3b2ee7..116d6d3ad3f0 100644
--- a/arch/powerpc/platforms/microwatt/Makefile
+++ b/arch/powerpc/platforms/microwatt/Makefile
@@ -1 +1 @@
-obj-y += setup.o
+obj-y += setup.o rng.o
diff --git a/arch/powerpc/platforms/microwatt/rng.c
b/arch/powerpc/platforms/microwatt/rng.c
new file mode 100644
index ..3d8ee6eb7dad
--- /dev/null
+++ b/arch/powerpc/platforms/microwatt/rng.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Derived from arch/powerpc/platforms/powernv/rng.c, which is:
+ * Copyright 2013, Michael Ellerman, IBM Corporation.
+ */
+
+#define pr_fmt(fmt)"microwatt-rng: " fmt
+
+#include
+#include
+#include
+#include
+#include
+
+#define DARN_ERR 0xul
+
+int microwatt_get_random_darn(unsigned long *v)
+{
+ unsigned long val;
+
+ /* Using DARN with L=1 - 64-bit conditioned random number */
+ asm volatile(PPC_DARN(%0, 1) : "=r"(val));
+
+ if (val == DARN_ERR)
+ return 0;
+
+ *v = val;
+
+ return 1;
+}
+
+static __init int rng_init(void)
+{
+ unsigned long val;
+ int i;
+
+ for (i = 0; i < 10; i++) {
+ if (microwatt_get_random_darn()) {
+ ppc_md.get_random_seed = microwatt_get_random_darn;
+ return 0;
+ }
+ }
+
+ pr_warn("Unable to use DARN for get_random_seed()\n");
+
+ return -EIO;
+}
+machine_subsys_initcall(, rng_init);
--
2.31.1
