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    Subject[PATCH 4.9 07/29] powerpc/powernv: wire up rng during setup_arch
    Date
    From: Jason A. Donenfeld <Jason@zx2c4.com>

    commit f3eac426657d985b97c92fa5f7ae1d43f04721f3 upstream.

    The platform's RNG must be available before random_init() in order to be
    useful for initial seeding, which in turn means that it needs to be
    called from setup_arch(), rather than from an init call.

    Complicating things, however, is that POWER8 systems need some per-cpu
    state and kmalloc, which isn't available at this stage. So we split
    things up into an early phase and a later opportunistic phase. This
    commit also removes some noisy log messages that don't add much.

    Fixes: a4da0d50b2a0 ("powerpc: Implement arch_get_random_long/int() for powernv")
    Cc: stable@vger.kernel.org # v3.13+
    Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
    Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
    [mpe: Add of_node_put(), use pnv naming, minor change log editing]
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Link: https://lore.kernel.org/r/20220621140849.127227-1-Jason@zx2c4.com
    Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/powerpc/include/asm/ppc-opcode.h | 4 +
    arch/powerpc/platforms/powernv/powernv.h | 2
    arch/powerpc/platforms/powernv/rng.c | 91 ++++++++++++++++++++++++++-----
    arch/powerpc/platforms/powernv/setup.c | 2
    4 files changed, 85 insertions(+), 14 deletions(-)

    --- a/arch/powerpc/include/asm/ppc-opcode.h
    +++ b/arch/powerpc/include/asm/ppc-opcode.h
    @@ -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
    @@ -328,6 +329,9 @@

    /* 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) | \
    + (((l) & 0x3) << 16))
    #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 | \
    --- a/arch/powerpc/platforms/powernv/powernv.h
    +++ b/arch/powerpc/platforms/powernv/powernv.h
    @@ -27,4 +27,6 @@ extern void opal_event_shutdown(void);

    bool cpu_core_split_required(void);

    +void pnv_rng_init(void);
    +
    #endif /* _POWERNV_H */
    --- a/arch/powerpc/platforms/powernv/rng.c
    +++ b/arch/powerpc/platforms/powernv/rng.c
    @@ -16,11 +16,14 @@
    #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>
    #include <asm/smp.h>
    +#include "powernv.h"

    +#define DARN_ERR 0xFFFFFFFFFFFFFFFFul

    struct powernv_rng {
    void __iomem *regs;
    @@ -30,7 +33,6 @@ struct powernv_rng {

    static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng);

    -
    int powernv_hwrng_present(void)
    {
    struct powernv_rng *rng;
    @@ -45,7 +47,11 @@ static unsigned long rng_whiten(struct p
    unsigned long parity;

    /* Calculate the parity of the value */
    - asm ("popcntd %0,%1" : "=r" (parity) : "r" (val));
    + asm (".machine push; \
    + .machine power7; \
    + popcntd %0,%1; \
    + .machine pop;"
    + : "=r" (parity) : "r" (val));

    /* xor our value with the previous mask */
    val ^= rng->mask;
    @@ -67,6 +73,38 @@ int powernv_get_random_real_mode(unsigne
    return 1;
    }

    +static int powernv_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 int __init initialise_darn(void)
    +{
    + unsigned long val;
    + int i;
    +
    + if (!cpu_has_feature(CPU_FTR_ARCH_300))
    + return -ENODEV;
    +
    + for (i = 0; i < 10; i++) {
    + if (powernv_get_random_darn(&val)) {
    + ppc_md.get_random_seed = powernv_get_random_darn;
    + return 0;
    + }
    + }
    + return -EIO;
    +}
    +
    int powernv_get_random_long(unsigned long *v)
    {
    struct powernv_rng *rng;
    @@ -88,7 +126,7 @@ static __init void rng_init_per_cpu(stru

    chip_id = of_get_ibm_chip_id(dn);
    if (chip_id == -1)
    - pr_warn("No ibm,chip-id found for %s.\n", dn->full_name);
    + pr_warn("No ibm,chip-id found for %pOF.\n", dn);

    for_each_possible_cpu(cpu) {
    if (per_cpu(powernv_rng, cpu) == NULL ||
    @@ -126,30 +164,55 @@ static __init int rng_create(struct devi

    rng_init_per_cpu(rng, dn);

    - pr_info_once("Registering arch random hook.\n");
    -
    ppc_md.get_random_seed = powernv_get_random_long;

    return 0;
    }

    -static __init int rng_init(void)
    +static int __init pnv_get_random_long_early(unsigned long *v)
    {
    struct device_node *dn;
    - int rc;
    +
    + if (!slab_is_available())
    + return 0;
    +
    + if (cmpxchg(&ppc_md.get_random_seed, pnv_get_random_long_early,
    + NULL) != pnv_get_random_long_early)
    + return 0;

    for_each_compatible_node(dn, NULL, "ibm,power-rng") {
    - rc = rng_create(dn);
    - if (rc) {
    - pr_err("Failed creating rng for %s (%d).\n",
    - dn->full_name, rc);
    + if (rng_create(dn))
    continue;
    - }
    -
    /* Create devices for hwrng driver */
    of_platform_device_create(dn, NULL, NULL);
    }

    + if (!ppc_md.get_random_seed)
    + return 0;
    + return ppc_md.get_random_seed(v);
    +}
    +
    +void __init pnv_rng_init(void)
    +{
    + struct device_node *dn;
    +
    + /* Prefer darn over the rest. */
    + if (!initialise_darn())
    + return;
    +
    + dn = of_find_compatible_node(NULL, NULL, "ibm,power-rng");
    + if (dn)
    + ppc_md.get_random_seed = pnv_get_random_long_early;
    +
    + of_node_put(dn);
    +}
    +
    +static int __init pnv_rng_late_init(void)
    +{
    + unsigned long v;
    + /* In case it wasn't called during init for some other reason. */
    + if (ppc_md.get_random_seed == pnv_get_random_long_early)
    + pnv_get_random_long_early(&v);
    return 0;
    }
    -machine_subsys_initcall(powernv, rng_init);
    +machine_subsys_initcall(powernv, pnv_rng_late_init);
    --- a/arch/powerpc/platforms/powernv/setup.c
    +++ b/arch/powerpc/platforms/powernv/setup.c
    @@ -168,6 +168,8 @@ static void __init pnv_setup_arch(void)
    powersave_nap = 1;

    /* XXX PMCS */
    +
    + pnv_rng_init();
    }

    static void __init pnv_init(void)

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