From: Radu Rendec rrendec@redhat.com
commit 6539cffa94957241c096099a57d05fa4d8c7db8a upstream
This patch gives architecture specific code the ability to initialize the cache level and allocate cacheinfo memory early, when cache level initialization runs on the primary CPU for all possible CPUs.
This is part of a patch series that attempts to further the work in commit 5944ce092b97 ("arch_topology: Build cacheinfo from primary CPU"). Previously, in the absence of any DT/ACPI cache info, architecture specific cache detection and info allocation for secondary CPUs would happen in non-preemptible context during early CPU initialization and trigger a "BUG: sleeping function called from invalid context" splat on an RT kernel.
More specifically, this patch adds the early_cache_level() function, which is called by fetch_cache_info() as a fallback when the number of cache leaves cannot be extracted from DT/ACPI. In the default generic (weak) implementation, this new function returns -ENOENT, which preserves the original behavior for architectures that do not implement the function.
Since early detection can get the number of cache leaves wrong in some cases*, additional logic is added to still call init_cache_level() later on the secondary CPU, therefore giving the architecture specific code an opportunity to go back and fix the initial guess. Again, the original behavior is preserved for architectures that do not implement the new function.
* For example, on arm64, CLIDR_EL1 detection works only when it runs on the current CPU. In other words, a CPU cannot detect the cache depth for any other CPU than itself.
Signed-off-by: Radu Rendec rrendec@redhat.com Reviewed-by: Pierre Gondois pierre.gondois@arm.com Link: https://lore.kernel.org/r/20230412185759.755408-2-rrendec@redhat.com Signed-off-by: Sudeep Holla sudeep.holla@arm.com Signed-off-by: Florian Fainelli florian.fainelli@broadcom.com --- drivers/base/cacheinfo.c | 75 +++++++++++++++++++++++++++------------ include/linux/cacheinfo.h | 2 ++ 2 files changed, 55 insertions(+), 22 deletions(-)
diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c index 8120ac1ddbe4..14aa62c3f10f 100644 --- a/drivers/base/cacheinfo.c +++ b/drivers/base/cacheinfo.c @@ -437,6 +437,11 @@ static void free_cache_attributes(unsigned int cpu) cache_shared_cpu_map_remove(cpu); }
+int __weak early_cache_level(unsigned int cpu) +{ + return -ENOENT; +} + int __weak init_cache_level(unsigned int cpu) { return -ENOENT; @@ -462,56 +467,82 @@ int allocate_cache_info(int cpu)
int fetch_cache_info(unsigned int cpu) { - struct cpu_cacheinfo *this_cpu_ci; + struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu); unsigned int levels = 0, split_levels = 0; 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) + if (!ret) { + 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 (ret || !cache_leaves(cpu)) { + ret = early_cache_level(cpu); + if (ret) 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; + + this_cpu_ci->early_ci_levels = true; } - if (!cache_leaves(cpu)) - return -ENOENT;
return allocate_cache_info(cpu); }
-int detect_cache_attributes(unsigned int cpu) +static inline int init_level_allocate_ci(unsigned int cpu) { - int ret; + unsigned int early_leaves = cache_leaves(cpu);
/* Since early initialization/allocation of the cacheinfo is allowed * via fetch_cache_info() and this also gets called as CPU hotplug * callbacks via cacheinfo_cpu_online, the init/alloc can be skipped * as it will happen only once (the cacheinfo memory is never freed). - * Just populate the cacheinfo. + * Just populate the cacheinfo. However, if the cacheinfo has been + * allocated early through the arch-specific early_cache_level() call, + * there is a chance the info is wrong (this can happen on arm64). In + * that case, call init_cache_level() anyway to give the arch-specific + * code a chance to make things right. */ - if (per_cpu_cacheinfo(cpu)) - goto populate_leaves; + if (per_cpu_cacheinfo(cpu) && !ci_cacheinfo(cpu)->early_ci_levels) + return 0;
if (init_cache_level(cpu) || !cache_leaves(cpu)) return -ENOENT;
- ret = allocate_cache_info(cpu); + /* + * Now that we have properly initialized the cache level info, make + * sure we don't try to do that again the next time we are called + * (e.g. as CPU hotplug callbacks). + */ + ci_cacheinfo(cpu)->early_ci_levels = false; + + if (cache_leaves(cpu) <= early_leaves) + return 0; + + kfree(per_cpu_cacheinfo(cpu)); + return allocate_cache_info(cpu); +} + +int detect_cache_attributes(unsigned int cpu) +{ + int ret; + + ret = init_level_allocate_ci(cpu); if (ret) return ret;
-populate_leaves: /* * If LLC is valid the cache leaves were already populated so just go to * update the cpu map. diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h index b91cc9991c7c..a5cfd44fab45 100644 --- a/include/linux/cacheinfo.h +++ b/include/linux/cacheinfo.h @@ -76,9 +76,11 @@ struct cpu_cacheinfo { unsigned int num_levels; unsigned int num_leaves; bool cpu_map_populated; + bool early_ci_levels; };
struct cpu_cacheinfo *get_cpu_cacheinfo(unsigned int cpu); +int early_cache_level(unsigned int cpu); int init_cache_level(unsigned int cpu); int init_of_cache_level(unsigned int cpu); int populate_cache_leaves(unsigned int cpu);