Re: [PATCH v8 1/2] powerpc/pseries: Interface to represent PAPR firmware attributes
From: Pratik Sampat
Date: Tue Sep 28 2021 - 08:43:53 EST
Hello Greg,
Thank you for your review.
On 28/09/21 5:38 pm, Greg KH wrote:
On Tue, Sep 28, 2021 at 05:21:01PM +0530, Pratik R. Sampat wrote:
Adds a generic interface to represent the energy and frequency related
PAPR attributes on the system using the new H_CALL
"H_GET_ENERGY_SCALE_INFO".
H_GET_EM_PARMS H_CALL was previously responsible for exporting this
information in the lparcfg, however the H_GET_EM_PARMS H_CALL
will be deprecated P10 onwards.
The H_GET_ENERGY_SCALE_INFO H_CALL is of the following call format:
hcall(
uint64 H_GET_ENERGY_SCALE_INFO, // Get energy scale info
uint64 flags, // Per the flag request
uint64 firstAttributeId,// The attribute id
uint64 bufferAddress, // Guest physical address of the output buffer
uint64 bufferSize // The size in bytes of the output buffer
);
This H_CALL can query either all the attributes at once with
firstAttributeId = 0, flags = 0 as well as query only one attribute
at a time with firstAttributeId = id, flags = 1.
The output buffer consists of the following
1. number of attributes - 8 bytes
2. array offset to the data location - 8 bytes
3. version info - 1 byte
4. A data array of size num attributes, which contains the following:
a. attribute ID - 8 bytes
b. attribute value in number - 8 bytes
c. attribute name in string - 64 bytes
d. attribute value in string - 64 bytes
The new H_CALL exports information in direct string value format, hence
a new interface has been introduced in
/sys/firmware/papr/energy_scale_info to export this information to
userspace in an extensible pass-through format.
The H_CALL returns the name, numeric value and string value (if exists)
The format of exposing the sysfs information is as follows:
/sys/firmware/papr/energy_scale_info/
|-- <id>/
|-- desc
|-- value
|-- value_desc (if exists)
|-- <id>/
|-- desc
|-- value
|-- value_desc (if exists)
...
The energy information that is exported is useful for userspace tools
such as powerpc-utils. Currently these tools infer the
"power_mode_data" value in the lparcfg, which in turn is obtained from
the to be deprecated H_GET_EM_PARMS H_CALL.
On future platforms, such userspace utilities will have to look at the
data returned from the new H_CALL being populated in this new sysfs
interface and report this information directly without the need of
interpretation.
Signed-off-by: Pratik R. Sampat <psampat@xxxxxxxxxxxxx>
Reviewed-by: Gautham R. Shenoy <ego@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Fabiano Rosas <farosas@xxxxxxxxxxxxx>
Reviewed-by: Kajol Jain <kjain@xxxxxxxxxxxxx>
---
.../sysfs-firmware-papr-energy-scale-info | 26 ++
arch/powerpc/include/asm/hvcall.h | 24 +-
arch/powerpc/kvm/trace_hv.h | 1 +
arch/powerpc/platforms/pseries/Makefile | 3 +-
.../pseries/papr_platform_attributes.c | 312 ++++++++++++++++++
5 files changed, 364 insertions(+), 2 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-firmware-papr-energy-scale-info
create mode 100644 arch/powerpc/platforms/pseries/papr_platform_attributes.c
diff --git a/Documentation/ABI/testing/sysfs-firmware-papr-energy-scale-info b/Documentation/ABI/testing/sysfs-firmware-papr-energy-scale-info
new file mode 100644
index 000000000000..139a576c7c9d
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-firmware-papr-energy-scale-info
@@ -0,0 +1,26 @@
+What: /sys/firmware/papr/energy_scale_info
+Date: June 2021
+Contact: Linux for PowerPC mailing list <linuxppc-dev@xxxxxxxxxx>
+Description: Directory hosting a set of platform attributes like
+ energy/frequency on Linux running as a PAPR guest.
+
+ Each file in a directory contains a platform
+ attribute hierarchy pertaining to performance/
+ energy-savings mode and processor frequency.
+
+What: /sys/firmware/papr/energy_scale_info/<id>
+ /sys/firmware/papr/energy_scale_info/<id>/desc
+ /sys/firmware/papr/energy_scale_info/<id>/value
+ /sys/firmware/papr/energy_scale_info/<id>/value_desc
+Date: June 2021
+Contact: Linux for PowerPC mailing list <linuxppc-dev@xxxxxxxxxx>
+Description: Energy, frequency attributes directory for POWERVM servers
+
+ This directory provides energy, frequency, folding information. It
+ contains below sysfs attributes:
+
+ - desc: String description of the attribute <id>
+
+ - value: Numeric value of attribute <id>
+
+ - value_desc: String value of attribute <id>
Can you just make 4 different entries in this file, making it easier to
parse and extend over time?
Do you mean I only create one file per attribute and populate it with 4
different entries as follows?
# cat /sys/firmware/papr/energy_scale_info/<id>
id:
desc:
value:
value_desc:
diff --git a/arch/powerpc/include/asm/hvcall.h b/arch/powerpc/include/asm/hvcall.h
index 9bcf345cb208..38980fef7a3d 100644
--- a/arch/powerpc/include/asm/hvcall.h
+++ b/arch/powerpc/include/asm/hvcall.h
@@ -323,7 +323,8 @@
#define H_SCM_PERFORMANCE_STATS 0x418
#define H_RPT_INVALIDATE 0x448
#define H_SCM_FLUSH 0x44C
-#define MAX_HCALL_OPCODE H_SCM_FLUSH
+#define H_GET_ENERGY_SCALE_INFO 0x450
+#define MAX_HCALL_OPCODE H_GET_ENERGY_SCALE_INFO
/* Scope args for H_SCM_UNBIND_ALL */
#define H_UNBIND_SCOPE_ALL (0x1)
@@ -641,6 +642,27 @@ struct hv_gpci_request_buffer {
uint8_t bytes[HGPCI_MAX_DATA_BYTES];
} __packed;
+#define ESI_VERSION 0x1
+#define MAX_ESI_ATTRS 10
+#define MAX_BUF_SZ (sizeof(struct h_energy_scale_info_hdr) + \
+ (sizeof(struct energy_scale_attribute) * MAX_ESI_ATTRS))
+
+struct energy_scale_attribute {
+ __be64 id;
+ __be64 value;
+ unsigned char desc[64];
+ unsigned char value_desc[64];
+} __packed;
+
+struct h_energy_scale_info_hdr {
+ __be64 num_attrs;
+ __be64 array_offset;
+ __u8 data_header_version;
+} __packed;
+
+/* /sys/firmware/papr */
+extern struct kobject *papr_kobj;
+
#endif /* __ASSEMBLY__ */
#endif /* __KERNEL__ */
#endif /* _ASM_POWERPC_HVCALL_H */
diff --git a/arch/powerpc/kvm/trace_hv.h b/arch/powerpc/kvm/trace_hv.h
index 830a126e095d..38cd0ed0a617 100644
--- a/arch/powerpc/kvm/trace_hv.h
+++ b/arch/powerpc/kvm/trace_hv.h
@@ -115,6 +115,7 @@
{H_VASI_STATE, "H_VASI_STATE"}, \
{H_ENABLE_CRQ, "H_ENABLE_CRQ"}, \
{H_GET_EM_PARMS, "H_GET_EM_PARMS"}, \
+ {H_GET_ENERGY_SCALE_INFO, "H_GET_ENERGY_SCALE_INFO"}, \
{H_SET_MPP, "H_SET_MPP"}, \
{H_GET_MPP, "H_GET_MPP"}, \
{H_HOME_NODE_ASSOCIATIVITY, "H_HOME_NODE_ASSOCIATIVITY"}, \
diff --git a/arch/powerpc/platforms/pseries/Makefile b/arch/powerpc/platforms/pseries/Makefile
index 4cda0ef87be0..c4c19f6a5975 100644
--- a/arch/powerpc/platforms/pseries/Makefile
+++ b/arch/powerpc/platforms/pseries/Makefile
@@ -6,7 +6,8 @@ obj-y := lpar.o hvCall.o nvram.o reconfig.o \
of_helpers.o \
setup.o iommu.o event_sources.o ras.o \
firmware.o power.o dlpar.o mobility.o rng.o \
- pci.o pci_dlpar.o eeh_pseries.o msi.o
+ pci.o pci_dlpar.o eeh_pseries.o msi.o \
+ papr_platform_attributes.o
obj-$(CONFIG_SMP) += smp.o
obj-$(CONFIG_SCANLOG) += scanlog.o
obj-$(CONFIG_KEXEC_CORE) += kexec.o
diff --git a/arch/powerpc/platforms/pseries/papr_platform_attributes.c b/arch/powerpc/platforms/pseries/papr_platform_attributes.c
new file mode 100644
index 000000000000..84ddce52e519
--- /dev/null
+++ b/arch/powerpc/platforms/pseries/papr_platform_attributes.c
@@ -0,0 +1,312 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Platform energy and frequency attributes driver
+ *
+ * This driver creates a sys file at /sys/firmware/papr/ which encapsulates a
+ * directory structure containing files in keyword - value pairs that specify
+ * energy and frequency configuration of the system.
+ *
+ * The format of exposing the sysfs information is as follows:
+ * /sys/firmware/papr/energy_scale_info/
+ * |-- <id>/
+ * |-- desc
+ * |-- value
+ * |-- value_desc (if exists)
+ * |-- <id>/
+ * |-- desc
+ * |-- value
+ * |-- value_desc (if exists)
+ *
+ * Copyright 2021 IBM Corp.
+ */
+
+#include <asm/hvcall.h>
+#include <asm/machdep.h>
+
+#include "pseries.h"
+
+/*
+ * Flag attributes to fetch either all or one attribute from the HCALL
+ * flag = BE(0) => fetch all attributes with firstAttributeId = 0
+ * flag = BE(1) => fetch a single attribute with firstAttributeId = id
+ */
+#define ESI_FLAGS_ALL 0
+#define ESI_FLAGS_SINGLE PPC_BIT(0)
+
+#define MAX_ATTRS 3
+
+struct papr_attr {
+ u64 id;
+ struct kobj_attribute kobj_attr;
Why does an attribute have to be part of this structure?
I bundled both an attribute as well as its ID in a structure because each
attributes value could only be queried from the firmware with the corresponding
ID.
It seemed to be logically connected and that's why I had them in the structure.
Are you suggesting we maintain them separately and don't need the coupling?
+};
+struct papr_group {
+ struct attribute_group pg;
+ struct papr_attr pgattrs[MAX_ATTRS];
+} *pgs;
+
+/* /sys/firmware/papr */
+struct kobject *papr_kobj;
+/* /sys/firmware/papr/energy_scale_info */
+struct kobject *esi_kobj;
+
+/*
+ * Extract and export the description of the energy scale attributes
+ */
+static ssize_t papr_show_desc(struct kobject *kobj,
+ struct kobj_attribute *kobj_attr,
+ char *buf)
+{
+ struct papr_attr *pattr = container_of(kobj_attr, struct papr_attr,
+ kobj_attr);
+ struct h_energy_scale_info_hdr *t_hdr;
+ struct energy_scale_attribute *t_esi;
+ char *t_buf;
+ int ret = 0;
+
+ t_buf = kmalloc(MAX_BUF_SZ, GFP_KERNEL);
+ if (t_buf == NULL)
+ return -ENOMEM;
+
+ ret = plpar_hcall_norets(H_GET_ENERGY_SCALE_INFO, ESI_FLAGS_SINGLE,
+ pattr->id, virt_to_phys(t_buf),
+ MAX_BUF_SZ);
+
+ if (ret != H_SUCCESS) {
+ pr_warn("hcall failed: H_GET_ENERGY_SCALE_INFO");
+ goto out;
+ }
+
+ t_hdr = (struct h_energy_scale_info_hdr *) t_buf;
+ t_esi = (struct energy_scale_attribute *)
+ (t_buf + be64_to_cpu(t_hdr->array_offset));
+
+ ret = snprintf(buf, sizeof(t_esi->desc), "%s\n", t_esi->desc);
+ if (ret < 0)
+ ret = -EIO;
+out:
+ kfree(t_buf);
+
+ return ret;
+}
+
+/*
+ * Extract and export the numeric value of the energy scale attributes
+ */
+static ssize_t papr_show_value(struct kobject *kobj,
+ struct kobj_attribute *kobj_attr,
+ char *buf)
+{
+ struct papr_attr *pattr = container_of(kobj_attr, struct papr_attr,
+ kobj_attr);
+ struct h_energy_scale_info_hdr *t_hdr;
+ struct energy_scale_attribute *t_esi;
+ char *t_buf;
+ int ret = 0;
+
+ t_buf = kmalloc(MAX_BUF_SZ, GFP_KERNEL);
+ if (t_buf == NULL)
+ return -ENOMEM;
+
+ ret = plpar_hcall_norets(H_GET_ENERGY_SCALE_INFO, ESI_FLAGS_SINGLE,
+ pattr->id, virt_to_phys(t_buf),
+ MAX_BUF_SZ);
+
+ if (ret != H_SUCCESS) {
+ pr_warn("hcall failed: H_GET_ENERGY_SCALE_INFO");
+ goto out;
+ }
+
+ t_hdr = (struct h_energy_scale_info_hdr *) t_buf;
+ t_esi = (struct energy_scale_attribute *)
+ (t_buf + be64_to_cpu(t_hdr->array_offset));
+
+ ret = snprintf(buf, sizeof(t_esi->value), "%llu\n",
+ be64_to_cpu(t_esi->value));
sysfs_emit() for when writing out to a sysfs file please. Same
elsewhere in this file.
Sure, I can use sysfs_emit for writing to a sysfs file.
+ if (ret < 0)
+ ret = -EIO;
+out:
+ kfree(t_buf);
+
+ return ret;
+}
+
+/*
+ * Extract and export the value description in string format of the energy
+ * scale attributes
+ */
+static ssize_t papr_show_value_desc(struct kobject *kobj,
+ struct kobj_attribute *kobj_attr,
+ char *buf)
+{
+ struct papr_attr *pattr = container_of(kobj_attr, struct papr_attr,
+ kobj_attr);
+ struct h_energy_scale_info_hdr *t_hdr;
+ struct energy_scale_attribute *t_esi;
+ char *t_buf;
+ int ret = 0;
+
+ t_buf = kmalloc(MAX_BUF_SZ, GFP_KERNEL);
+ if (t_buf == NULL)
+ return -ENOMEM;
+
+ ret = plpar_hcall_norets(H_GET_ENERGY_SCALE_INFO, ESI_FLAGS_SINGLE,
+ pattr->id, virt_to_phys(t_buf),
+ MAX_BUF_SZ);
+
+ if (ret != H_SUCCESS) {
+ pr_warn("hcall failed: H_GET_ENERGY_SCALE_INFO");
+ goto out;
+ }
+
+ t_hdr = (struct h_energy_scale_info_hdr *) t_buf;
+ t_esi = (struct energy_scale_attribute *)
+ (t_buf + be64_to_cpu(t_hdr->array_offset));
+
+ ret = snprintf(buf, sizeof(t_esi->value_desc), "%s\n",
+ t_esi->value_desc);
+ if (ret < 0)
+ ret = -EIO;
+out:
+ kfree(t_buf);
+
+ return ret;
+}
+
+static struct papr_ops_info {
+ const char *attr_name;
+ ssize_t (*show)(struct kobject *kobj, struct kobj_attribute *kobj_attr,
+ char *buf);
+} ops_info[MAX_ATTRS] = {
+ { "desc", papr_show_desc },
+ { "value", papr_show_value },
+ { "value_desc", papr_show_value_desc },
What is wrong with just using the __ATTR_RO() macro and then having an
array of attributes in a single group? That should be a lot simpler
overall, right?
If I understand this correctly, you mean I can have a array of attributes in a
flat single group?
I suppose that would be a simpler, given your earlier suggestion to wrap
attribute values up in a single file per attribute.
However, the intent of grouping and keeping files separate was that each sysfs
file has only one value to display.
I can change it to using an array of attributes in a single group too if you
believe that is right way to go instead.
+};
+
+static void add_attr(u64 id, int index, struct papr_attr *attr)
+{
+ attr->id = id;
+ sysfs_attr_init(&attr->kobj_attr.attr);
+ attr->kobj_attr.attr.name = ops_info[index].attr_name;
+ attr->kobj_attr.attr.mode = 0444;
+ attr->kobj_attr.show = ops_info[index].show;
If you do the above, no need for this function at all.
+}
+
+static int add_attr_group(u64 id, struct papr_group *pg, bool show_val_desc)
+{
+ int i;
+
+ for (i = 0; i < MAX_ATTRS; i++) {
+ if (!strcmp(ops_info[i].attr_name, "value_desc") &&
+ !show_val_desc) {
+ continue;
+ }
+ add_attr(id, i, &pg->pgattrs[i]);
+ pg->pg.attrs[i] = &pg->pgattrs[i].kobj_attr.attr;
+ }
+
+ return sysfs_create_group(esi_kobj, &pg->pg);
Again, if you just have a list of attributes, there's no need for this
function either.
I think this can be a lot simpler than you are currently making it.
I agree, if the groups are eliminated, then all the complexity of adding a
attribute groups vanishes as well.
Thanks for your feedback again.
Pratik
thanks,
greg k-h