powerpc/powernv: utilising darn instruction for get_random_seed on p9
PATCH 1/1 powerpc/powernv: utilising darn instruction for get_random_seed on p9
Currently ppc_md.get_random_seed uses the powernv_get_random_long function. A guest calling this function would have to go through the hypervisor. The 'darn' instruction, introduced in power 9, allows us to bypass this by directly obtaining a value from the mmio region.
This patch adds an alternative function for ppc_md.get_random_seed on p9, utilising the darn instruction.
Signed-off-by Matt Brown <[email protected]>
--- arch/powerpc/include/asm/ppc-opcode.h | 4 ++++ arch/powerpc/platforms/powernv/rng.c | 23 ++++++++++++++++++++++- 2 files changed, 26 insertions(+), 1 deletion(-)
arch/powerpc/include/asm/ppc-opcode.h +4 -0
@@ -134,6 +134,7 @@#define PPC_INST_COPY 0x7c00060c#define PPC_INST_COPY_FIRST 0x7c20060c#define PPC_INST_CP_ABORT 0x7c00068c +#define PPC_INST_DARN 0x7c0005e6#define PPC_INST_DCBA 0x7c0005ec#define PPC_INST_DCBA_MASK 0xfc0007fe#define PPC_INST_DCBAL 0x7c2005ec
@@ -325,6 +326,9 @@/* Deal with instructions that older assemblers aren't aware of */ #define PPC_CP_ABORT stringify_in_c(.long PPC_INST_CP_ABORT) +#define PPC_DARN (t, l) stringify_in_c(.long PPC_INST_DARN | \ + ___PPC_RT(t) | \ + ___PPC_RA(l))#define PPC_DCBAL (a, b) stringify_in_c(.long PPC_INST_DCBAL | \ __PPC_RA(a) | __PPC_RB(b))#define PPC_DCBZL (a, b) stringify_in_c(.long PPC_INST_DCBZL | \
arch/powerpc/platforms/powernv/rng.c +22 -1
@@ -8,6 +8,7 @@*/ #define pr_fmt (fmt) "powernv-rng: " fmt +#define DARN_ERR 0xFFFFFFFFFFFFFFFFul#include <linux/kernel.h> #include <linux/of.h>
@@ -16,6 +17,7 @@#include <linux/slab.h> #include <linux/smp.h> #include <asm/archrandom.h> +#include <asm/cputable.h> #include <asm/io.h> #include <asm/prom.h> #include <asm/machdep.h>
@@ -67,6 +69,22 @@ int powernv_get_random_real_mode(unsigned long *v)return 1 ; } +int powernv_get_random_darn (unsigned long *v) +{ +int n =0 ; +unsigned long val; + +do { +/* Using DARN with L=1 - conditioned random number */ + asm (PPC_DARN(%0, 1)"\n" : "=r"(val) :); + n++; + }while (val ==DARN_ERR && n <10 ); + + *v = val; + +return (val ==DARN_ERR ) ?0 :1 ; +} +int powernv_get_random_long (unsigned long *v) {struct powernv_rng *rng;
@@ -128,7 +146,10 @@ static __init int rng_create(struct device_node *dn)pr_info_once ("Registering arch random hook.\n" ); - ppc_md.get_random_seed = powernv_get_random_long; +if (cpu_has_feature (CPU_FTR_ARCH_300 )) + ppc_md.get_random_seed = powernv_get_random_darn; +else + ppc_md.get_random_seed = powernv_get_random_long;return 0 ; }
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2.9.3