// SPDX-License-Identifier: GPL-2.0-only
#define pr_fmt(fmt) "rtas-work-area: " fmt
#include <linux/genalloc.h>
#include <linux/log2.h>
#include <linux/kernel.h>
#include <linux/memblock.h>
#include <linux/mempool.h>
#include <linux/minmax.h>
#include <linux/mutex.h>
#include <linux/numa.h>
#include <linux/sizes.h>
#include <linux/wait.h>
#include <asm/machdep.h>
#include <asm/rtas-work-area.h>
#include <asm/rtas.h>
enum {
/*
* Ensure the pool is page-aligned.
*/
RTAS_WORK_AREA_ARENA_ALIGN = PAGE_SIZE,
/*
* Don't let a single allocation claim the whole arena.
*/
RTAS_WORK_AREA_ARENA_SZ = RTAS_WORK_AREA_MAX_ALLOC_SZ * 2,
/*
* The smallest known work area size is for ibm,get-vpd's
* location code argument, which is limited to 79 characters
* plus 1 nul terminator.
*
* PAPR+ 7.3.20 ibm,get-vpd RTAS Call
* PAPR+ 12.3.2.4 Converged Location Code Rules - Length Restrictions
*/
RTAS_WORK_AREA_MIN_ALLOC_SZ = roundup_pow_of_two(80),
};
static struct {
struct gen_pool *gen_pool;
char *arena;
struct mutex mutex; /* serializes allocations */
struct wait_queue_head wqh;
mempool_t descriptor_pool;
bool available;
} rwa_state = {
.mutex = __MUTEX_INITIALIZER(rwa_state.mutex),
.wqh = __WAIT_QUEUE_HEAD_INITIALIZER(rwa_state.wqh),
};
/*
* A single work area buffer and descriptor to serve requests early in
* boot before the allocator is fully initialized. We know 4KB is the
* most any boot time user needs (they all call ibm,get-system-parameter).
*/
static bool early_work_area_in_use __initdata;
static char early_work_area_buf[SZ_4K] __initdata __aligned(SZ_4K);
static struct rtas_work_area early_work_area __initdata = {
.buf = early_work_area_buf,
.size = sizeof(early_work_area_buf),
};
static struct rtas_work_area * __init rtas_work_area_alloc_early(size_t size)
{
WARN_ON(size > early_work_area.size);
WARN_ON(early_work_area_in_use);
early_work_area_in_use = true;
memset(early_work_area.buf, 0, early_work_area.size);
return &early_work_area;
}
static void __init rtas_work_area_free_early(struct rtas_work_area *work_area)
{
WARN_ON(work_area != &early_work_area);
WARN_ON(!early_work_area_in_use);
early_work_area_in_use = false;
}
struct rtas_work_area * __ref __rtas_work_area_alloc(size_t size)
{
struct rtas_work_area *area;
unsigned long addr;
might_sleep();
/*
* The rtas_work_area_alloc() wrapper enforces this at build
* time. Requests that exceed the arena size will block
* indefinitely.
*/
WARN_ON(size > RTAS_WORK_AREA_MAX_ALLOC_SZ);
if (!rwa_state.available)
return rtas_work_area_alloc_early(size);
/*
* To ensure FCFS behavior and prevent a high rate of smaller
* requests from starving larger ones, use the mutex to queue
* allocations.
*/
mutex_lock(&rwa_state.mutex);
wait_event(rwa_state.wqh,
(addr = gen_pool_alloc(rwa_state.gen_pool, size)) != 0);
mutex_unlock(&rwa_state.mutex);
area = mempool_alloc(&rwa_state.descriptor_pool, GFP_KERNEL);
area->buf = (char *)addr;
area->size = size;
return area;
}
void __ref rtas_work_area_free(struct rtas_work_area *area)
{
if (!rwa_state.available) {
rtas_work_area_free_early(area);
return;
}
gen_pool_free(rwa_state.gen_pool, (unsigned long)area->buf, area->size);
mempool_free(area, &rwa_state.descriptor_pool);
wake_up(&rwa_state.wqh);
}
/*
* Initialization of the work area allocator happens in two parts. To
* reliably reserve an arena that satisfies RTAS addressing
* requirements, we must perform a memblock allocation early,
* immmediately after RTAS instantiation. Then we have to wait until
* the slab allocator is up before setting up the descriptor mempool
* and adding the arena to a gen_pool.
*/
static __init int rtas_work_area_allocator_init(void)
{
const unsigned int order = ilog2(RTAS_WORK_AREA_MIN_ALLOC_SZ);
const phys_addr_t pa_start = __pa(rwa_state.arena);
const phys_addr_t pa_end = pa_start + RTAS_WORK_AREA_ARENA_SZ - 1;
struct gen_pool *pool;
const int nid = NUMA_NO_NODE;
int err;
err = -ENOMEM;
if (!rwa_state.arena)
goto err_out;
pool = gen_pool_create(order, nid);
if (!pool)
goto err_out;
/*
* All RTAS functions that consume work areas are OK with
* natural alignment, when they have alignment requirements at
* all.
*/
gen_pool_set_algo(pool, gen_pool_first_fit_order_align, NULL);
err = gen_pool_add(pool, (unsigned long)rwa_state.arena,
RTAS_WORK_AREA_ARENA_SZ, nid);
if (err)
goto err_destroy;
err = mempool_init_kmalloc_pool(&rwa_state.descriptor_pool, 1,
sizeof(struct rtas_work_area));
if (err)
goto err_destroy;
rwa_state.gen_pool = pool;
rwa_state.available = true;
pr_debug("arena [%pa-%pa] (%uK), min/max alloc sizes %u/%u\n",
&pa_start, &pa_end,
RTAS_WORK_AREA_ARENA_SZ / SZ_1K,
RTAS_WORK_AREA_MIN_ALLOC_SZ,
RTAS_WORK_AREA_MAX_ALLOC_SZ);
return 0;
err_destroy:
gen_pool_destroy(pool);
err_out:
return err;
}
machine_arch_initcall(pseries, rtas_work_area_allocator_init);
/**
* rtas_work_area_reserve_arena() - Reserve memory suitable for RTAS work areas.
* @limit: Upper limit for memblock allocation.
*/
void __init rtas_work_area_reserve_arena(const phys_addr_t limit)
{
const phys_addr_t align = RTAS_WORK_AREA_ARENA_ALIGN;
const phys_addr_t size = RTAS_WORK_AREA_ARENA_SZ;
const phys_addr_t min = MEMBLOCK_LOW_LIMIT;
const int nid = NUMA_NO_NODE;
/*
* Too early for a machine_is(pseries) check. But PAPR
* effectively mandates that ibm,get-system-parameter is
* present:
*
* R1–7.3.16–1. All platforms must support the System
* Parameters option.
*
* So set up the arena if we find that, with a fallback to
* ibm,configure-connector, just in case.
*/
if (rtas_function_implemented(RTAS_FN_IBM_GET_SYSTEM_PARAMETER) ||
rtas_function_implemented(RTAS_FN_IBM_CONFIGURE_CONNECTOR))
rwa_state.arena = memblock_alloc_try_nid(size, align, min, limit, nid);
}
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