Commit 5944ce09 authored by Pierre Gondois's avatar Pierre Gondois Committed by Sudeep Holla

arch_topology: Build cacheinfo from primary CPU

commit 3fcbf1c7 ("arch_topology: Fix cache attributes detection
in the CPU hotplug path")
adds a call to detect_cache_attributes() to populate the cacheinfo
before updating the siblings mask. detect_cache_attributes() allocates
memory and can take the PPTT mutex (on ACPI platforms). On PREEMPT_RT
kernels, on secondary CPUs, this triggers a:
  'BUG: sleeping function called from invalid context' [1]
as the code is executed with preemption and interrupts disabled.

The primary CPU was previously storing the cache information using
the now removed (struct cpu_topology).llc_id:
commit 5b8dc787 ("arch_topology: Drop LLC identifier stash from
the CPU topology")

allocate_cache_info() tries to build the cacheinfo from the primary
CPU prior secondary CPUs boot, if the DT/ACPI description
contains cache information.
If allocate_cache_info() fails, then fallback to the current state
for the cacheinfo allocation. [1] will be triggered in such case.

When unplugging a CPU, the cacheinfo memory cannot be freed. If it
was, then the memory would be allocated early by the re-plugged
CPU and would trigger [1].

Note that populate_cache_leaves() might be called multiple times
due to populate_leaves being moved up. This is required since
detect_cache_attributes() might be called with per_cpu_cacheinfo(cpu)
being allocated but not populated.

[1]:
 | BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:46
 | in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 0, name: swapper/111
 | preempt_count: 1, expected: 0
 | RCU nest depth: 1, expected: 1
 | 3 locks held by swapper/111/0:
 |  #0:  (&pcp->lock){+.+.}-{3:3}, at: get_page_from_freelist+0x218/0x12c8
 |  #1:  (rcu_read_lock){....}-{1:3}, at: rt_spin_trylock+0x48/0xf0
 |  #2:  (&zone->lock){+.+.}-{3:3}, at: rmqueue_bulk+0x64/0xa80
 | irq event stamp: 0
 | hardirqs last  enabled at (0):  0x0
 | hardirqs last disabled at (0):  copy_process+0x5dc/0x1ab8
 | softirqs last  enabled at (0):  copy_process+0x5dc/0x1ab8
 | softirqs last disabled at (0):  0x0
 | Preemption disabled at:
 |  migrate_enable+0x30/0x130
 | CPU: 111 PID: 0 Comm: swapper/111 Tainted: G        W          6.0.0-rc4-rt6-[...]
 | Call trace:
 |  __kmalloc+0xbc/0x1e8
 |  detect_cache_attributes+0x2d4/0x5f0
 |  update_siblings_masks+0x30/0x368
 |  store_cpu_topology+0x78/0xb8
 |  secondary_start_kernel+0xd0/0x198
 |  __secondary_switched+0xb0/0xb4
Signed-off-by: default avatarPierre Gondois <pierre.gondois@arm.com>
Reviewed-by: default avatarSudeep Holla <sudeep.holla@arm.com>
Acked-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
Link: https://lore.kernel.org/r/20230104183033.755668-7-pierre.gondois@arm.comSigned-off-by: default avatarSudeep Holla <sudeep.holla@arm.com>
parent bd500361
...@@ -113,11 +113,6 @@ static void fill_cacheinfo(struct cacheinfo **this_leaf, ...@@ -113,11 +113,6 @@ static void fill_cacheinfo(struct cacheinfo **this_leaf,
} }
} }
int init_cache_level(unsigned int cpu)
{
return init_of_cache_level(cpu);
}
int populate_cache_leaves(unsigned int cpu) int populate_cache_leaves(unsigned int cpu)
{ {
struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu); struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
......
...@@ -736,7 +736,7 @@ void update_siblings_masks(unsigned int cpuid) ...@@ -736,7 +736,7 @@ void update_siblings_masks(unsigned int cpuid)
ret = detect_cache_attributes(cpuid); ret = detect_cache_attributes(cpuid);
if (ret && ret != -ENOENT) if (ret && ret != -ENOENT)
pr_info("Early cacheinfo failed, ret = %d\n", ret); pr_info("Early cacheinfo allocation failed, ret = %d\n", ret);
/* update core and thread sibling masks */ /* update core and thread sibling masks */
for_each_online_cpu(cpu) { for_each_online_cpu(cpu) {
...@@ -825,7 +825,7 @@ __weak int __init parse_acpi_topology(void) ...@@ -825,7 +825,7 @@ __weak int __init parse_acpi_topology(void)
#if defined(CONFIG_ARM64) || defined(CONFIG_RISCV) #if defined(CONFIG_ARM64) || defined(CONFIG_RISCV)
void __init init_cpu_topology(void) void __init init_cpu_topology(void)
{ {
int ret; int cpu, ret;
reset_cpu_topology(); reset_cpu_topology();
ret = parse_acpi_topology(); ret = parse_acpi_topology();
...@@ -840,6 +840,14 @@ void __init init_cpu_topology(void) ...@@ -840,6 +840,14 @@ void __init init_cpu_topology(void)
reset_cpu_topology(); reset_cpu_topology();
return; return;
} }
for_each_possible_cpu(cpu) {
ret = fetch_cache_info(cpu);
if (ret) {
pr_err("Early cacheinfo failed, ret = %d\n", ret);
break;
}
}
} }
void store_cpu_topology(unsigned int cpuid) void store_cpu_topology(unsigned int cpuid)
......
...@@ -389,10 +389,6 @@ static void free_cache_attributes(unsigned int cpu) ...@@ -389,10 +389,6 @@ static void free_cache_attributes(unsigned int cpu)
return; return;
cache_shared_cpu_map_remove(cpu); cache_shared_cpu_map_remove(cpu);
kfree(per_cpu_cacheinfo(cpu));
per_cpu_cacheinfo(cpu) = NULL;
cache_leaves(cpu) = 0;
} }
int __weak init_cache_level(unsigned int cpu) int __weak init_cache_level(unsigned int cpu)
...@@ -405,29 +401,71 @@ int __weak populate_cache_leaves(unsigned int cpu) ...@@ -405,29 +401,71 @@ int __weak populate_cache_leaves(unsigned int cpu)
return -ENOENT; return -ENOENT;
} }
static inline
int allocate_cache_info(int cpu)
{
per_cpu_cacheinfo(cpu) = kcalloc(cache_leaves(cpu),
sizeof(struct cacheinfo), GFP_ATOMIC);
if (!per_cpu_cacheinfo(cpu)) {
cache_leaves(cpu) = 0;
return -ENOMEM;
}
return 0;
}
int fetch_cache_info(unsigned int cpu)
{
struct cpu_cacheinfo *this_cpu_ci;
unsigned int levels, split_levels;
int ret;
if (acpi_disabled) {
ret = init_of_cache_level(cpu);
if (ret < 0)
return ret;
} else {
ret = acpi_get_cache_info(cpu, &levels, &split_levels);
if (ret < 0)
return ret;
this_cpu_ci = get_cpu_cacheinfo(cpu);
this_cpu_ci->num_levels = levels;
/*
* This assumes that:
* - there cannot be any split caches (data/instruction)
* above a unified cache
* - data/instruction caches come by pair
*/
this_cpu_ci->num_leaves = levels + split_levels;
}
if (!cache_leaves(cpu))
return -ENOENT;
return allocate_cache_info(cpu);
}
int detect_cache_attributes(unsigned int cpu) int detect_cache_attributes(unsigned int cpu)
{ {
int ret; int ret;
/* Since early detection of the cacheinfo is allowed via this /* Since early initialization/allocation of the cacheinfo is allowed
* function and this also gets called as CPU hotplug callbacks via * via fetch_cache_info() and this also gets called as CPU hotplug
* cacheinfo_cpu_online, the initialisation can be skipped and only * callbacks via cacheinfo_cpu_online, the init/alloc can be skipped
* CPU maps can be updated as the CPU online status would be update * as it will happen only once (the cacheinfo memory is never freed).
* if called via cacheinfo_cpu_online path. * Just populate the cacheinfo.
*/ */
if (per_cpu_cacheinfo(cpu)) if (per_cpu_cacheinfo(cpu))
goto update_cpu_map; goto populate_leaves;
if (init_cache_level(cpu) || !cache_leaves(cpu)) if (init_cache_level(cpu) || !cache_leaves(cpu))
return -ENOENT; return -ENOENT;
per_cpu_cacheinfo(cpu) = kcalloc(cache_leaves(cpu), ret = allocate_cache_info(cpu);
sizeof(struct cacheinfo), GFP_ATOMIC); if (ret)
if (per_cpu_cacheinfo(cpu) == NULL) { return ret;
cache_leaves(cpu) = 0;
return -ENOMEM;
}
populate_leaves:
/* /*
* populate_cache_leaves() may completely setup the cache leaves and * populate_cache_leaves() may completely setup the cache leaves and
* shared_cpu_map or it may leave it partially setup. * shared_cpu_map or it may leave it partially setup.
...@@ -436,7 +474,6 @@ int detect_cache_attributes(unsigned int cpu) ...@@ -436,7 +474,6 @@ int detect_cache_attributes(unsigned int cpu)
if (ret) if (ret)
goto free_ci; goto free_ci;
update_cpu_map:
/* /*
* For systems using DT for cache hierarchy, fw_token * For systems using DT for cache hierarchy, fw_token
* and shared_cpu_map will be set up here only if they are * and shared_cpu_map will be set up here only if they are
......
...@@ -85,6 +85,7 @@ int populate_cache_leaves(unsigned int cpu); ...@@ -85,6 +85,7 @@ int populate_cache_leaves(unsigned int cpu);
int cache_setup_acpi(unsigned int cpu); int cache_setup_acpi(unsigned int cpu);
bool last_level_cache_is_valid(unsigned int cpu); bool last_level_cache_is_valid(unsigned int cpu);
bool last_level_cache_is_shared(unsigned int cpu_x, unsigned int cpu_y); bool last_level_cache_is_shared(unsigned int cpu_x, unsigned int cpu_y);
int fetch_cache_info(unsigned int cpu);
int detect_cache_attributes(unsigned int cpu); int detect_cache_attributes(unsigned int cpu);
#ifndef CONFIG_ACPI_PPTT #ifndef CONFIG_ACPI_PPTT
/* /*
......
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