[PATCH v3 0/3] arch_topology/cacheinfo: Fixes for v5.20

[PATCH v3 0/3] arch_topology/cacheinfo: Fixes for v5.20

[Sudeep Holla]

These are fixes for the cacheinfo/arch_topology updates containing [0]
queued currently in the -next via [3].

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

---
Changes in v3 from v2[2]:
	- Dropped mapping and unmapping of PPTT at runtime using
	  acpi_{get,put}_table() to avoid "BUG: sleeping function
	  called from invalid context"
	- Added tested-by from Geert

Changes in v2[2] from v1[1]:
        - Changed the cacheinfo per-cpu allocation to be atomic
	  to fix possible "BUG: sleeping function called from invalid context"
        - Added all the received tags

[0] https://lore.kernel.org/all/20220704101605.1318280-1-sudeep.holla@arm.com
[1] https://lore.kernel.org/all/20220713133344.1201247-1-sudeep.holla@arm.com
[2] https://lore.kernel.org/all/20220715102609.2160689-1-sudeep.holla@arm.com
[3] https://lore.kernel.org/all/20220706124644.2276077-1-sudeep.holla@arm.com

---
Sudeep Holla (3):
      cacheinfo: Use atomic allocation for percpu cache attributes
      ACPI: PPTT: Leave the table mapped for the runtime usage
      arch_topology: Fix cache attributes detection in the CPU hotplug path

 drivers/acpi/pptt.c          | 102 ++++++++++++++++++++-----------------------
 drivers/base/arch_topology.c |  16 +++----
 drivers/base/cacheinfo.c     |   2 +-
 3 files changed, 54 insertions(+), 66 deletions(-)
---
base-commit: 7128af87c7f1c30cd6cebe0b012cc25872c689e2
change-id: 20220720-arch_topo_fixes-d91d43827aeb

Best regards,
-- 
Regards,
Sudeep


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[PATCH v3 1/3] cacheinfo: Use atomic allocation for percpu cache attributes

[Sudeep Holla]

On couple of architectures like RISC-V and ARM64, we need to detect
cache attribues quite early during the boot when the secondary CPUs
start. So we will call detect_cache_attributes in the atomic context
and since use of normal allocation can sleep, we will end up getting
"sleeping in the atomic context" bug splat.

In order avoid that, move the allocation to use atomic version in
preparation to move the actual detection of cache attributes in the
CPU hotplug path which is atomic.

Cc: Ionela Voinescu <ionela.voinescu@arm.com>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index 65d566ff24c4..4b5cd08c5a65 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -356,7 +356,7 @@ int detect_cache_attributes(unsigned int cpu)
 		return -ENOENT;
 
 	per_cpu_cacheinfo(cpu) = kcalloc(cache_leaves(cpu),
-					 sizeof(struct cacheinfo), GFP_KERNEL);
+					 sizeof(struct cacheinfo), GFP_ATOMIC);
 	if (per_cpu_cacheinfo(cpu) == NULL) {
 		cache_leaves(cpu) = 0;
 		return -ENOMEM;

-- 
b4 0.10.0-dev-54fef

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[PATCH v3 2/3] ACPI: PPTT: Leave the table mapped for the runtime usage

[Sudeep Holla]

Currently, everytime an information needs to be fetched from the PPTT,
the table is mapped via acpi_get_table() and unmapped after the use via
acpi_put_table() which is fine. However we do this at runtime especially
when the CPU is hotplugged out and plugged in back since we re-populate
the cache topology and other information.

However, with the support to fetch LLC information from the PPTT in the
cpuhotplug path which is executed in the atomic context, it is preferred
to avoid mapping and unmapping of the PPTT for every single use as the
acpi_get_table() might sleep waiting for a mutex.

In order to avoid the same, the table is needs to just mapped once on
the boot CPU and is never unmapped allowing it to be used at runtime
with out the hassle of mapping and unmapping the table.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

--

Hi Rafael,

Sorry to bother you again on this PPTT changes. Guenter reported an issue
with lockdep enabled in -next that include my cacheinfo/arch_topology changes
to utilise LLC from PPTT in the CPU hotplug path.

Please ack the change once you are happy so that I can get it merged with
other fixes via Greg's tree.

Regards,
Sudeep

diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
index dd3222a15c9c..c91342dcbcd6 100644
--- a/drivers/acpi/pptt.c
+++ b/drivers/acpi/pptt.c
@@ -533,21 +533,37 @@ static int topology_get_acpi_cpu_tag(struct acpi_table_header *table,
 	return -ENOENT;
 }
 
+
+static struct acpi_table_header *acpi_get_pptt(void)
+{
+	static struct acpi_table_header *pptt;
+	acpi_status status;
+
+	/*
+	 * PPTT will be used at runtime on every CPU hotplug in path, so we
+	 * don't need to call acpi_put_table() to release the table mapping.
+	 */
+	if (!pptt) {
+		status = acpi_get_table(ACPI_SIG_PPTT, 0, &pptt);
+		if (ACPI_FAILURE(status))
+			acpi_pptt_warn_missing();
+	}
+
+	return pptt;
+}
+
 static int find_acpi_cpu_topology_tag(unsigned int cpu, int level, int flag)
 {
 	struct acpi_table_header *table;
-	acpi_status status;
 	int retval;
 
-	status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
-	if (ACPI_FAILURE(status)) {
-		acpi_pptt_warn_missing();
+	table = acpi_get_pptt();
+	if (!table)
 		return -ENOENT;
-	}
+
 	retval = topology_get_acpi_cpu_tag(table, cpu, level, flag);
 	pr_debug("Topology Setup ACPI CPU %d, level %d ret = %d\n",
 		 cpu, level, retval);
-	acpi_put_table(table);
 
 	return retval;
 }
@@ -568,16 +584,13 @@ static int find_acpi_cpu_topology_tag(unsigned int cpu, int level, int flag)
 static int check_acpi_cpu_flag(unsigned int cpu, int rev, u32 flag)
 {
 	struct acpi_table_header *table;
-	acpi_status status;
 	u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
 	struct acpi_pptt_processor *cpu_node = NULL;
 	int ret = -ENOENT;
 
-	status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
-	if (ACPI_FAILURE(status)) {
-		acpi_pptt_warn_missing();
-		return ret;
-	}
+	table = acpi_get_pptt();
+	if (!table)
+		return -ENOENT;
 
 	if (table->revision >= rev)
 		cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
@@ -585,8 +598,6 @@ static int check_acpi_cpu_flag(unsigned int cpu, int rev, u32 flag)
 	if (cpu_node)
 		ret = (cpu_node->flags & flag) != 0;
 
-	acpi_put_table(table);
-
 	return ret;
 }
 
@@ -605,18 +616,15 @@ int acpi_find_last_cache_level(unsigned int cpu)
 	u32 acpi_cpu_id;
 	struct acpi_table_header *table;
 	int number_of_levels = 0;
-	acpi_status status;
+
+	table = acpi_get_pptt();
+	if (!table)
+		return -ENOENT;
 
 	pr_debug("Cache Setup find last level CPU=%d\n", cpu);
 
 	acpi_cpu_id = get_acpi_id_for_cpu(cpu);
-	status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
-	if (ACPI_FAILURE(status)) {
-		acpi_pptt_warn_missing();
-	} else {
-		number_of_levels = acpi_find_cache_levels(table, acpi_cpu_id);
-		acpi_put_table(table);
-	}
+	number_of_levels = acpi_find_cache_levels(table, acpi_cpu_id);
 	pr_debug("Cache Setup find last level level=%d\n", number_of_levels);
 
 	return number_of_levels;
@@ -638,20 +646,16 @@ int acpi_find_last_cache_level(unsigned int cpu)
 int cache_setup_acpi(unsigned int cpu)
 {
 	struct acpi_table_header *table;
-	acpi_status status;
-
-	pr_debug("Cache Setup ACPI CPU %d\n", cpu);
 
-	status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
-	if (ACPI_FAILURE(status)) {
-		acpi_pptt_warn_missing();
+	table = acpi_get_pptt();
+	if (!table)
 		return -ENOENT;
-	}
+
+	pr_debug("Cache Setup ACPI CPU %d\n", cpu);
 
 	cache_setup_acpi_cpu(table, cpu);
-	acpi_put_table(table);
 
-	return status;
+	return 0;
 }
 
 /**
@@ -730,50 +734,38 @@ int find_acpi_cpu_topology_package(unsigned int cpu)
 int find_acpi_cpu_topology_cluster(unsigned int cpu)
 {
 	struct acpi_table_header *table;
-	acpi_status status;
 	struct acpi_pptt_processor *cpu_node, *cluster_node;
 	u32 acpi_cpu_id;
 	int retval;
 	int is_thread;
 
-	status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
-	if (ACPI_FAILURE(status)) {
-		acpi_pptt_warn_missing();
+	table = acpi_get_pptt();
+	if (!table)
 		return -ENOENT;
-	}
 
 	acpi_cpu_id = get_acpi_id_for_cpu(cpu);
 	cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
-	if (cpu_node == NULL || !cpu_node->parent) {
-		retval = -ENOENT;
-		goto put_table;
-	}
+	if (!cpu_node || !cpu_node->parent)
+		return -ENOENT;
 
 	is_thread = cpu_node->flags & ACPI_PPTT_ACPI_PROCESSOR_IS_THREAD;
 	cluster_node = fetch_pptt_node(table, cpu_node->parent);
-	if (cluster_node == NULL) {
-		retval = -ENOENT;
-		goto put_table;
-	}
+	if (!cluster_node)
+		return -ENOENT;
+
 	if (is_thread) {
-		if (!cluster_node->parent) {
-			retval = -ENOENT;
-			goto put_table;
-		}
+		if (!cluster_node->parent)
+			return -ENOENT;
+
 		cluster_node = fetch_pptt_node(table, cluster_node->parent);
-		if (cluster_node == NULL) {
-			retval = -ENOENT;
-			goto put_table;
-		}
+		if (!cluster_node)
+			return -ENOENT;
 	}
 	if (cluster_node->flags & ACPI_PPTT_ACPI_PROCESSOR_ID_VALID)
 		retval = cluster_node->acpi_processor_id;
 	else
 		retval = ACPI_PTR_DIFF(cluster_node, table);
 
-put_table:
-	acpi_put_table(table);
-
 	return retval;
 }
 

-- 
b4 0.10.0-dev-54fef

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Re: [PATCH v3 2/3] ACPI: PPTT: Leave the table mapped for the runtime usage

[Rafael J. Wysocki]

On Wed, Jul 20, 2022 at 2:56 PM Sudeep Holla <sudeep.holla@arm.com> wrote:
>
> Currently, everytime an information needs to be fetched from the PPTT,
> the table is mapped via acpi_get_table() and unmapped after the use via
> acpi_put_table() which is fine. However we do this at runtime especially
> when the CPU is hotplugged out and plugged in back since we re-populate
> the cache topology and other information.
>
> However, with the support to fetch LLC information from the PPTT in the
> cpuhotplug path which is executed in the atomic context, it is preferred
> to avoid mapping and unmapping of the PPTT for every single use as the
> acpi_get_table() might sleep waiting for a mutex.
>
> In order to avoid the same, the table is needs to just mapped once on
> the boot CPU and is never unmapped allowing it to be used at runtime
> with out the hassle of mapping and unmapping the table.
>
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Cc: Rafael J. Wysocki <rafael@kernel.org>
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
>
> --
>
> Hi Rafael,
>
> Sorry to bother you again on this PPTT changes. Guenter reported an issue
> with lockdep enabled in -next that include my cacheinfo/arch_topology changes
> to utilise LLC from PPTT in the CPU hotplug path.
>
> Please ack the change once you are happy so that I can get it merged with
> other fixes via Greg's tree.

OK

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

>
> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> index dd3222a15c9c..c91342dcbcd6 100644
> --- a/drivers/acpi/pptt.c
> +++ b/drivers/acpi/pptt.c
> @@ -533,21 +533,37 @@ static int topology_get_acpi_cpu_tag(struct acpi_table_header *table,
>         return -ENOENT;
>  }
>
> +
> +static struct acpi_table_header *acpi_get_pptt(void)
> +{
> +       static struct acpi_table_header *pptt;
> +       acpi_status status;
> +
> +       /*
> +        * PPTT will be used at runtime on every CPU hotplug in path, so we
> +        * don't need to call acpi_put_table() to release the table mapping.
> +        */
> +       if (!pptt) {
> +               status = acpi_get_table(ACPI_SIG_PPTT, 0, &pptt);
> +               if (ACPI_FAILURE(status))
> +                       acpi_pptt_warn_missing();
> +       }
> +
> +       return pptt;
> +}
> +
>  static int find_acpi_cpu_topology_tag(unsigned int cpu, int level, int flag)
>  {
>         struct acpi_table_header *table;
> -       acpi_status status;
>         int retval;
>
> -       status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
> -       if (ACPI_FAILURE(status)) {
> -               acpi_pptt_warn_missing();
> +       table = acpi_get_pptt();
> +       if (!table)
>                 return -ENOENT;
> -       }
> +
>         retval = topology_get_acpi_cpu_tag(table, cpu, level, flag);
>         pr_debug("Topology Setup ACPI CPU %d, level %d ret = %d\n",
>                  cpu, level, retval);
> -       acpi_put_table(table);
>
>         return retval;
>  }
> @@ -568,16 +584,13 @@ static int find_acpi_cpu_topology_tag(unsigned int cpu, int level, int flag)
>  static int check_acpi_cpu_flag(unsigned int cpu, int rev, u32 flag)
>  {
>         struct acpi_table_header *table;
> -       acpi_status status;
>         u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
>         struct acpi_pptt_processor *cpu_node = NULL;
>         int ret = -ENOENT;
>
> -       status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
> -       if (ACPI_FAILURE(status)) {
> -               acpi_pptt_warn_missing();
> -               return ret;
> -       }
> +       table = acpi_get_pptt();
> +       if (!table)
> +               return -ENOENT;
>
>         if (table->revision >= rev)
>                 cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
> @@ -585,8 +598,6 @@ static int check_acpi_cpu_flag(unsigned int cpu, int rev, u32 flag)
>         if (cpu_node)
>                 ret = (cpu_node->flags & flag) != 0;
>
> -       acpi_put_table(table);
> -
>         return ret;
>  }
>
> @@ -605,18 +616,15 @@ int acpi_find_last_cache_level(unsigned int cpu)
>         u32 acpi_cpu_id;
>         struct acpi_table_header *table;
>         int number_of_levels = 0;
> -       acpi_status status;
> +
> +       table = acpi_get_pptt();
> +       if (!table)
> +               return -ENOENT;
>
>         pr_debug("Cache Setup find last level CPU=%d\n", cpu);
>
>         acpi_cpu_id = get_acpi_id_for_cpu(cpu);
> -       status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
> -       if (ACPI_FAILURE(status)) {
> -               acpi_pptt_warn_missing();
> -       } else {
> -               number_of_levels = acpi_find_cache_levels(table, acpi_cpu_id);
> -               acpi_put_table(table);
> -       }
> +       number_of_levels = acpi_find_cache_levels(table, acpi_cpu_id);
>         pr_debug("Cache Setup find last level level=%d\n", number_of_levels);
>
>         return number_of_levels;
> @@ -638,20 +646,16 @@ int acpi_find_last_cache_level(unsigned int cpu)
>  int cache_setup_acpi(unsigned int cpu)
>  {
>         struct acpi_table_header *table;
> -       acpi_status status;
> -
> -       pr_debug("Cache Setup ACPI CPU %d\n", cpu);
>
> -       status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
> -       if (ACPI_FAILURE(status)) {
> -               acpi_pptt_warn_missing();
> +       table = acpi_get_pptt();
> +       if (!table)
>                 return -ENOENT;
> -       }
> +
> +       pr_debug("Cache Setup ACPI CPU %d\n", cpu);
>
>         cache_setup_acpi_cpu(table, cpu);
> -       acpi_put_table(table);
>
> -       return status;
> +       return 0;
>  }
>
>  /**
> @@ -730,50 +734,38 @@ int find_acpi_cpu_topology_package(unsigned int cpu)
>  int find_acpi_cpu_topology_cluster(unsigned int cpu)
>  {
>         struct acpi_table_header *table;
> -       acpi_status status;
>         struct acpi_pptt_processor *cpu_node, *cluster_node;
>         u32 acpi_cpu_id;
>         int retval;
>         int is_thread;
>
> -       status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
> -       if (ACPI_FAILURE(status)) {
> -               acpi_pptt_warn_missing();
> +       table = acpi_get_pptt();
> +       if (!table)
>                 return -ENOENT;
> -       }
>
>         acpi_cpu_id = get_acpi_id_for_cpu(cpu);
>         cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
> -       if (cpu_node == NULL || !cpu_node->parent) {
> -               retval = -ENOENT;
> -               goto put_table;
> -       }
> +       if (!cpu_node || !cpu_node->parent)
> +               return -ENOENT;
>
>         is_thread = cpu_node->flags & ACPI_PPTT_ACPI_PROCESSOR_IS_THREAD;
>         cluster_node = fetch_pptt_node(table, cpu_node->parent);
> -       if (cluster_node == NULL) {
> -               retval = -ENOENT;
> -               goto put_table;
> -       }
> +       if (!cluster_node)
> +               return -ENOENT;
> +
>         if (is_thread) {
> -               if (!cluster_node->parent) {
> -                       retval = -ENOENT;
> -                       goto put_table;
> -               }
> +               if (!cluster_node->parent)
> +                       return -ENOENT;
> +
>                 cluster_node = fetch_pptt_node(table, cluster_node->parent);
> -               if (cluster_node == NULL) {
> -                       retval = -ENOENT;
> -                       goto put_table;
> -               }
> +               if (!cluster_node)
> +                       return -ENOENT;
>         }
>         if (cluster_node->flags & ACPI_PPTT_ACPI_PROCESSOR_ID_VALID)
>                 retval = cluster_node->acpi_processor_id;
>         else
>                 retval = ACPI_PTR_DIFF(cluster_node, table);
>
> -put_table:
> -       acpi_put_table(table);
> -
>         return retval;
>  }
>
>
> --
> b4 0.10.0-dev-54fef

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[PATCH v3 3/3] arch_topology: Fix cache attributes detection in the CPU hotplug path

[Sudeep Holla]

init_cpu_topology() is called only once at the boot and all the cache
attributes are detected early for all the possible CPUs. However when
the CPUs are hotplugged out, the cacheinfo gets removed. While the
attributes are added back when the CPUs are hotplugged back in as part
of CPU hotplug state machine, it ends up called quite late after the
update_siblings_masks() are called in the secondary_start_kernel()
resulting in wrong llc_sibling_masks.

Move the call to detect_cache_attributes() inside update_siblings_masks()
to ensure the cacheinfo is updated before the LLC sibling masks are
updated. This will fix the incorrect LLC sibling masks generated when
the CPUs are hotplugged out and hotplugged back in again.

Reported-by: Ionela Voinescu <ionela.voinescu@arm.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Ionela Voinescu <ionela.voinescu@arm.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Ionela Voinescu <ionela.voinescu@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 441e14ac33a4..0424b59b695e 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -732,7 +732,11 @@ const struct cpumask *cpu_clustergroup_mask(int cpu)
 void update_siblings_masks(unsigned int cpuid)
 {
 	struct cpu_topology *cpu_topo, *cpuid_topo = &cpu_topology[cpuid];
-	int cpu;
+	int cpu, ret;
+
+	ret = detect_cache_attributes(cpuid);
+	if (ret)
+		pr_info("Early cacheinfo failed, ret = %d\n", ret);
 
 	/* update core and thread sibling masks */
 	for_each_online_cpu(cpu) {
@@ -821,7 +825,7 @@ __weak int __init parse_acpi_topology(void)
 #if defined(CONFIG_ARM64) || defined(CONFIG_RISCV)
 void __init init_cpu_topology(void)
 {
-	int ret, cpu;
+	int ret;
 
 	reset_cpu_topology();
 	ret = parse_acpi_topology();
@@ -836,13 +840,5 @@ void __init init_cpu_topology(void)
 		reset_cpu_topology();
 		return;
 	}
-
-	for_each_possible_cpu(cpu) {
-		ret = detect_cache_attributes(cpu);
-		if (ret) {
-			pr_info("Early cacheinfo failed, ret = %d\n", ret);
-			break;
-		}
-	}
 }
 #endif

-- 
b4 0.10.0-dev-54fef

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