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Michal Suchanek |
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From e66ca3db5917f4bcad039d3a3df9f1003797c249 Mon Sep 17 00:00:00 2001
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Michal Suchanek |
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From: Matt Brown <matthew.brown.dev@gmail.com>
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Michal Suchanek |
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Date: Fri, 4 Aug 2017 11:12:18 +1000
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Michal Suchanek |
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Subject: [PATCH] powerpc/powernv: Use darn instruction for get_random_seed()
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Michal Suchanek |
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on Power9
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References: bsc#1065729
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Patch-mainline: v4.14-rc1
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Git-commit: e66ca3db5917f4bcad039d3a3df9f1003797c249
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Michal Suchanek |
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Michal Suchanek |
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This adds powernv_get_random_darn() which utilises the darn instruction,
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introduced in ISA v3.0/POWER9.
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The darn instruction can potentially return an error, which is supported
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by the get_random_seed() API, in normal usage if we see an error we just
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return that to the caller.
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However when detecting whether darn is functional at boot we try up to
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10 times, before deciding that darn doesn't work and failing the
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registration of get_random_seed(). That way an intermittent failure
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at boot doesn't deprive the system of randomness until the next reboot.
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Michal Suchanek |
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Michal Suchanek |
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Signed-off-by: Matt Brown <matthew.brown.dev@gmail.com>
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[mpe: Move init into a function, tweak change log]
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Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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Acked-by: Michal Suchanek <msuchanek@suse.de>
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---
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arch/powerpc/include/asm/ppc-opcode.h | 4 +++
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arch/powerpc/platforms/powernv/rng.c | 39 +++++++++++++++++++++++++++
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2 files changed, 43 insertions(+)
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diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h
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index fa9ebaead91e..041ba15aa2b9 100644
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--- a/arch/powerpc/include/asm/ppc-opcode.h
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+++ b/arch/powerpc/include/asm/ppc-opcode.h
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@@ -193,6 +193,7 @@
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#define PPC_INST_CLRBHRB 0x7c00035c
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#define PPC_INST_COPY 0x7c20060c
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#define PPC_INST_CP_ABORT 0x7c00068c
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+#define PPC_INST_DARN 0x7c0005e6
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#define PPC_INST_DCBA 0x7c0005ec
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#define PPC_INST_DCBA_MASK 0xfc0007fe
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#define PPC_INST_DCBAL 0x7c2005ec
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@@ -395,6 +396,9 @@
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#define PPC_CP_ABORT stringify_in_c(.long PPC_INST_CP_ABORT)
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#define PPC_COPY(a, b) stringify_in_c(.long PPC_INST_COPY | \
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___PPC_RA(a) | ___PPC_RB(b))
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+#define PPC_DARN(t, l) stringify_in_c(.long PPC_INST_DARN | \
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+ ___PPC_RT(t) | \
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+ (((l) & 0x3) << 16))
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#define PPC_DCBAL(a, b) stringify_in_c(.long PPC_INST_DCBAL | \
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__PPC_RA(a) | __PPC_RB(b))
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#define PPC_DCBZL(a, b) stringify_in_c(.long PPC_INST_DCBZL | \
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diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c
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index 1a9d84371a4d..c5ce3a8bd4c9 100644
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--- a/arch/powerpc/platforms/powernv/rng.c
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+++ b/arch/powerpc/platforms/powernv/rng.c
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@@ -16,11 +16,13 @@
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#include <linux/slab.h>
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#include <linux/smp.h>
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#include <asm/archrandom.h>
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+#include <asm/cputable.h>
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#include <asm/io.h>
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#include <asm/prom.h>
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#include <asm/machdep.h>
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#include <asm/smp.h>
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+#define DARN_ERR 0xFFFFFFFFFFFFFFFFul
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struct powernv_rng {
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void __iomem *regs;
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@@ -67,6 +69,41 @@ int powernv_get_random_real_mode(unsigned long *v)
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return 1;
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}
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+int powernv_get_random_darn(unsigned long *v)
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+{
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+ unsigned long val;
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+
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+ /* Using DARN with L=1 - 64-bit conditioned random number */
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+ asm volatile(PPC_DARN(%0, 1) : "=r"(val));
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+
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+ if (val == DARN_ERR)
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+ return 0;
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+
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+ *v = val;
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+
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+ return 1;
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+}
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+
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+static int initialise_darn(void)
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+{
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+ unsigned long val;
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+ int i;
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+
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+ if (!cpu_has_feature(CPU_FTR_ARCH_300))
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+ return -ENODEV;
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+
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+ for (i = 0; i < 10; i++) {
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+ if (powernv_get_random_darn(&val)) {
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+ ppc_md.get_random_seed = powernv_get_random_darn;
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+ return 0;
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+ }
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+ }
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+
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+ pr_warn("Unable to use DARN for get_random_seed()\n");
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+
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+ return -EIO;
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+}
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+
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int powernv_get_random_long(unsigned long *v)
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{
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struct powernv_rng *rng;
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@@ -150,6 +187,8 @@ static __init int rng_init(void)
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of_platform_device_create(dn, NULL, NULL);
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}
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+ initialise_darn();
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+
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return 0;
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}
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machine_subsys_initcall(powernv, rng_init);
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--
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2.35.3
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