| Message ID | 20220621140849.127227-1-Jason@zx2c4.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [v5] powerpc/powernv: wire up rng during setup_arch | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/github-powerpc_selftests | success | Successfully ran 10 jobs. |
| snowpatch_ozlabs/github-powerpc_ppctests | success | Successfully ran 10 jobs. |
Le 21/06/2022 à 16:08, Jason A. Donenfeld a écrit : > 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. Fortunately, > each platform already has a setup_arch function pointer, which means we > can wire it up that way. 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. Regarding the kmalloc(), I have not looked at it in details, but usually you can use memblock_alloc() when kmalloc is not available yet. Christophe
Hi Christophe, On Tue, Jun 21, 2022 at 06:33:11PM +0000, Christophe Leroy wrote: > Le 21/06/2022 à 16:08, Jason A. Donenfeld a écrit : > > 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. Fortunately, > > each platform already has a setup_arch function pointer, which means we > > can wire it up that way. 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. > > Regarding the kmalloc(), I have not looked at it in details, but usually > you can use memblock_alloc() when kmalloc is not available yet. That seems a bit excessive, especially as those allocations are long lived. And we don't even *need* it that early, but just before random_init(). Michael is running this v5 on the test rig overnight, so we'll learn in the Australian morning whether this finally did the trick (I hope). Jason
Le 21/06/2022 à 20:47, Jason A. Donenfeld a écrit : > Hi Christophe, > > On Tue, Jun 21, 2022 at 06:33:11PM +0000, Christophe Leroy wrote: >> Le 21/06/2022 à 16:08, Jason A. Donenfeld a écrit : >>> 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. Fortunately, >>> each platform already has a setup_arch function pointer, which means we >>> can wire it up that way. 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. >> >> Regarding the kmalloc(), I have not looked at it in details, but usually >> you can use memblock_alloc() when kmalloc is not available yet. > > That seems a bit excessive, especially as those allocations are long > lived. And we don't even *need* it that early, but just before > random_init(). Michael is running this v5 on the test rig overnight, so > we'll learn in the Australian morning whether this finally did the trick > (I hope). > The fact that they are long lived make them a good candidate for memblock_alloc(). But fair enough, if they are not required that early then just do it later. Christophe
Christophe Leroy <christophe.leroy@csgroup.eu> writes: > Le 21/06/2022 à 20:47, Jason A. Donenfeld a écrit : >> On Tue, Jun 21, 2022 at 06:33:11PM +0000, Christophe Leroy wrote: >>> Le 21/06/2022 à 16:08, Jason A. Donenfeld a écrit : >>>> 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. Fortunately, >>>> each platform already has a setup_arch function pointer, which means we >>>> can wire it up that way. 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. >>> >>> Regarding the kmalloc(), I have not looked at it in details, but usually >>> you can use memblock_alloc() when kmalloc is not available yet. >> >> That seems a bit excessive, especially as those allocations are long >> lived. And we don't even *need* it that early, but just before >> random_init(). Michael is running this v5 on the test rig overnight, so >> we'll learn in the Australian morning whether this finally did the trick >> (I hope). > > The fact that they are long lived make them a good candidate for > memblock_alloc(). > > But fair enough, if they are not required that early then just do it later. memblock works but then we trip on ioremap vs early_ioremap. Fixing that is a bit of a pain as we'd have to stop using of_iomap() and we'd also need to switch the mappings to ioremap() later in boot. We'd also have to defer the percpu initialisation. So it's all just a bit of a pain when we actually only need to get the hook ready before random_init() which is called much later in boot when slab/ioremap/percpu are all ready. cheers
On Tue, 21 Jun 2022 16:08:49 +0200, Jason A. Donenfeld wrote: > 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. Fortunately, > each platform already has a setup_arch function pointer, which means we > can wire it up that way. 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. > > [...] Applied to powerpc/fixes. [1/1] powerpc/powernv: wire up rng during setup_arch https://git.kernel.org/powerpc/c/f3eac426657d985b97c92fa5f7ae1d43f04721f3 cheers
diff --git a/arch/powerpc/platforms/powernv/powernv.h b/arch/powerpc/platforms/powernv/powernv.h index e297bf4abfcb..fd3f5e1eb10b 100644 --- a/arch/powerpc/platforms/powernv/powernv.h +++ b/arch/powerpc/platforms/powernv/powernv.h @@ -42,4 +42,6 @@ ssize_t memcons_copy(struct memcons *mc, char *to, loff_t pos, size_t count); u32 __init memcons_get_size(struct memcons *mc); struct memcons *__init memcons_init(struct device_node *node, const char *mc_prop_name); +void powernv_rng_init(void); + #endif /* _POWERNV_H */ diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c index e3d44b36ae98..e332e72e1857 100644 --- a/arch/powerpc/platforms/powernv/rng.c +++ b/arch/powerpc/platforms/powernv/rng.c @@ -17,6 +17,7 @@ #include <asm/prom.h> #include <asm/machdep.h> #include <asm/smp.h> +#include "powernv.h" #define DARN_ERR 0xFFFFFFFFFFFFFFFFul @@ -28,7 +29,6 @@ struct powernv_rng { static DEFINE_PER_CPU(struct powernv_rng *, powernv_rng); - int powernv_hwrng_present(void) { struct powernv_rng *rng; @@ -98,9 +98,6 @@ static int __init initialise_darn(void) return 0; } } - - pr_warn("Unable to use DARN for get_random_seed()\n"); - return -EIO; } @@ -163,32 +160,50 @@ static __init int rng_create(struct device_node *dn) 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 powernv_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, powernv_get_random_long_early, + NULL) != powernv_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 %pOF (%d).\n", - dn, rc); + if (rng_create(dn)) continue; - } - /* Create devices for hwrng driver */ of_platform_device_create(dn, NULL, NULL); } - initialise_darn(); + if (!ppc_md.get_random_seed) + return 0; + return ppc_md.get_random_seed(v); +} + +void __init powernv_rng_init(void) +{ + /* Prefer darn over the rest. */ + if (!initialise_darn()) + return; + + if (of_find_compatible_node(NULL, NULL, "ibm,power-rng")) + ppc_md.get_random_seed = powernv_get_random_long_early; +} +static int __init powernv_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 == powernv_get_random_long_early) + powernv_get_random_long_early(&v); return 0; } -machine_subsys_initcall(powernv, rng_init); +machine_subsys_initcall(powernv, powernv_rng_late_init); diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c index 824c3ad7a0fa..a5fcb6796b22 100644 --- a/arch/powerpc/platforms/powernv/setup.c +++ b/arch/powerpc/platforms/powernv/setup.c @@ -203,6 +203,8 @@ static void __init pnv_setup_arch(void) pnv_check_guarded_cores(); /* XXX PMCS */ + + powernv_rng_init(); } static void __init pnv_init(void)