RFC: https://lkml.org/lkml/2021/6/4/791
PATCH v1: https://lkml.org/lkml/2021/6/16/805
Changelog v1 --> v2
Based on comments from Fabiano and Gautham, the following changes
were made:
1. Added flag attributes to fetch either single or all attributes from
the H_GET_ENERGY_SCALE_INFO HCALL
2. Seperated the header and the attribute structs, therfore allocating
for them through a single abstract buffer and later parsing them
into their own structures based on the offset
3. Renamed Energy Management(em) prefixed variables to energy scale
attributes(esi) prefixed variables to maintain consistency.
4. Removed bailing on version checks as to avoid faliure in future
versions which can be backwards compatible
5. Moved check for FW_FEATURE_LPAR before the HCALL is made to save
cycles and allocations on an event of faliure
6. Updated descriptions and comments
Also, have implemented a POC using this interface for the powerpc-utils'
ppc64_cpu --frequency command-line tool to utilize this information
in userspace.
The POC for the new interface has been hosted here:
https://github.com/pratiksampat/powerpc-utils/tree/H_GET_ENERGY_SCALE_INFO_v2
Sample output from the powerpc-utils tool is as follows:
# ppc64_cpu --frequency
Power and Performance Mode: XXXX
Idle Power Saver Status : XXXX
Processor Folding Status : XXXX --> Printed if Idle power save status is supported
Platform reported frequencies --> Frequencies reported from the platform's H_CALL i.e PAPR interface
min : NNNN GHz
max : NNNN GHz
static : NNNN GHz
Tool Computed frequencies
min : NNNN GHz (cpu XX)
max : NNNN GHz (cpu XX)
avg : NNNN GHz
Pratik R. Sampat (1):
powerpc/pseries: Interface to represent PAPR firmware attributes
.../sysfs-firmware-papr-energy-scale-info | 26 ++
arch/powerpc/include/asm/hvcall.h | 23 +-
arch/powerpc/kvm/trace_hv.h | 1 +
arch/powerpc/platforms/pseries/Makefile | 3 +-
.../pseries/papr_platform_attributes.c | 320 ++++++++++++++++++
5 files changed, 371 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
--
2.31.1
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 <[email protected]>
---
.../sysfs-firmware-papr-energy-scale-info | 26 ++
arch/powerpc/include/asm/hvcall.h | 23 +-
arch/powerpc/kvm/trace_hv.h | 1 +
arch/powerpc/platforms/pseries/Makefile | 3 +-
.../pseries/papr_platform_attributes.c | 320 ++++++++++++++++++
5 files changed, 371 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..fd82f2bfafe5
--- /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 <[email protected]>
+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 <[email protected]>
+Description: Energy, frequency attributes directory for POWERVM servers
+
+ This directory provides energy, erequency, 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>
diff --git a/arch/powerpc/include/asm/hvcall.h b/arch/powerpc/include/asm/hvcall.h
index e3b29eda8074..25a6b744d41e 100644
--- a/arch/powerpc/include/asm/hvcall.h
+++ b/arch/powerpc/include/asm/hvcall.h
@@ -316,7 +316,8 @@
#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)
@@ -631,6 +632,26 @@ struct hv_gpci_request_buffer {
uint8_t bytes[HGPCI_MAX_DATA_BYTES];
} __packed;
+#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 c8a2b0b05ac0..d14fca89ac25 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..117801bd7e76
--- /dev/null
+++ b/arch/powerpc/platforms/pseries/papr_platform_attributes.c
@@ -0,0 +1,320 @@
+// 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 <linux/module.h>
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/hugetlb.h>
+#include <asm/lppaca.h>
+#include <asm/hvcall.h>
+#include <asm/firmware.h>
+#include <asm/time.h>
+#include <asm/prom.h>
+#include <asm/vdso_datapage.h>
+#include <asm/vio.h>
+#include <asm/mmu.h>
+#include <asm/machdep.h>
+#include <asm/drmem.h>
+
+#include "pseries.h"
+
+#define MAX_ATTRS 3
+#define MAX_NAME_LEN 16
+
+/*
+ * 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)
+
+struct papr_attr {
+ u64 id;
+ struct kobj_attribute kobj_attr;
+};
+struct papr_group {
+ char name[MAX_NAME_LEN];
+ struct attribute_group pg;
+ struct papr_attr *pgattrs;
+} *pgs;
+
+/* /sys/firmware/papr */
+struct kobject *papr_kobj;
+/* /sys/firmware/papr/energy_scale_info */
+struct kobject *esi_kobj;
+
+struct h_energy_scale_info_hdr *esi_hdr;
+struct energy_scale_attribute *esi_attrs;
+
+/*
+ * Extract and export the description of the energy scale attribute
+ *
+ * As We do not expect the name to change, hence use the old description and
+ * save a call to the H_GET_ENERGY_SCALE_INFO HCALL
+ */
+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);
+ int idx, ret = 0;
+
+ for (idx = 0; idx < be64_to_cpu(esi_hdr->num_attrs); idx++) {
+ if (pattr->id == be64_to_cpu(esi_attrs[idx].id)) {
+ ret = sprintf(buf, "%s\n", esi_attrs[idx].desc);
+ if (ret < 0)
+ ret = -EIO;
+ break;
+ }
+ }
+
+ 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);
+ char *t_buf;
+ struct h_energy_scale_info_hdr *t_hdr;
+ struct energy_scale_attribute *t_esi;
+ 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 = sprintf(buf, "%llu\n", be64_to_cpu(t_esi->value));
+ 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);
+ char *t_buf;
+ struct h_energy_scale_info_hdr *t_hdr;
+ struct energy_scale_attribute *t_esi;
+ 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 = sprintf(buf, "%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 },
+};
+
+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;
+}
+
+static int add_attr_group(u64 id, int len, struct papr_group *pg,
+ bool show_val_desc)
+{
+ int i;
+
+ for (i = 0; i < len; 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);
+}
+
+static int __init papr_init(void)
+{
+ uint64_t num_attrs;
+ int ret, idx, i;
+ char *esi_buf;
+
+ if (!firmware_has_feature(FW_FEATURE_LPAR))
+ return -ENXIO;
+
+ esi_buf = kmalloc(MAX_BUF_SZ, GFP_KERNEL);
+ if (esi_buf == NULL)
+ return -ENOMEM;
+ /*
+ * 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
+ */
+ ret = plpar_hcall_norets(H_GET_ENERGY_SCALE_INFO, ESI_FLAGS_ALL, 0,
+ virt_to_phys(esi_buf), MAX_BUF_SZ);
+ if (ret != H_SUCCESS) {
+ pr_warn("hcall failed: H_GET_ENERGY_SCALE_INFO");
+ goto out;
+ }
+
+ esi_hdr = (struct h_energy_scale_info_hdr *) esi_buf;
+ num_attrs = be64_to_cpu(esi_hdr->num_attrs);
+ /*
+ * Typecast the energy buffer to the attribute structure at the offset
+ * specified in the buffer
+ */
+ esi_attrs = (struct energy_scale_attribute *)
+ (esi_buf + be64_to_cpu(esi_hdr->array_offset));
+
+ pgs = kcalloc(num_attrs, sizeof(*pgs), GFP_KERNEL);
+ if (!pgs)
+ goto out_pgs;
+
+ papr_kobj = kobject_create_and_add("papr", firmware_kobj);
+ if (!papr_kobj) {
+ pr_warn("kobject_create_and_add papr failed\n");
+ goto out_kobj;
+ }
+
+ esi_kobj = kobject_create_and_add("energy_scale_info", papr_kobj);
+ if (!esi_kobj) {
+ pr_warn("kobject_create_and_add energy_scale_info failed\n");
+ goto out_ekobj;
+ }
+
+ for (idx = 0; idx < num_attrs; idx++) {
+ char buf[4];
+ bool show_val_desc = true;
+
+ pgs[idx].pgattrs = kcalloc(MAX_ATTRS,
+ sizeof(*pgs[idx].pgattrs),
+ GFP_KERNEL);
+ if (!pgs[idx].pgattrs)
+ goto out_kobj;
+
+ pgs[idx].pg.attrs = kcalloc(MAX_ATTRS + 1,
+ sizeof(*pgs[idx].pg.attrs),
+ GFP_KERNEL);
+ if (!pgs[idx].pg.attrs) {
+ kfree(pgs[idx].pgattrs);
+ goto out_kobj;
+ }
+
+ sprintf(buf, "%lld", be64_to_cpu(esi_attrs[idx].id));
+ pgs[idx].pg.name = buf;
+
+ /* Do not add the value description if it does not exist */
+ if (strlen(esi_attrs[idx].value_desc) == 0)
+ show_val_desc = false;
+
+ if (add_attr_group(be64_to_cpu(esi_attrs[idx].id),
+ MAX_ATTRS, &pgs[idx], show_val_desc)) {
+ pr_warn("Failed to create papr attribute group %s\n",
+ pgs[idx].pg.name);
+ goto out_pgattrs;
+ }
+ }
+
+ return 0;
+
+out_pgattrs:
+ for (i = 0; i < MAX_ATTRS; i++) {
+ kfree(pgs[i].pgattrs);
+ kfree(pgs[i].pg.attrs);
+ }
+out_ekobj:
+ kobject_put(esi_kobj);
+out_kobj:
+ kobject_put(papr_kobj);
+out_pgs:
+ kfree(pgs);
+out:
+ kfree(esi_buf);
+
+ return -ENOMEM;
+}
+
+machine_device_initcall(pseries, papr_init);
--
2.31.1
Hello Pratik,
On Tue, Jul 06, 2021 at 01:54:00PM +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)
> ...
I like this implementation. Only one comment w.r.t versioning below:
[..snip..]
> @@ -631,6 +632,26 @@ struct hv_gpci_request_buffer {
> uint8_t bytes[HGPCI_MAX_DATA_BYTES];
> } __packed;
>
> +#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;
> +
[..snip..]
> +static int __init papr_init(void)
> +{
> + uint64_t num_attrs;
> + int ret, idx, i;
> + char *esi_buf;
> +
> + if (!firmware_has_feature(FW_FEATURE_LPAR))
> + return -ENXIO;
> +
> + esi_buf = kmalloc(MAX_BUF_SZ, GFP_KERNEL);
> + if (esi_buf == NULL)
> + return -ENOMEM;
> + /*
> + * 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
> + */
> + ret = plpar_hcall_norets(H_GET_ENERGY_SCALE_INFO, ESI_FLAGS_ALL, 0,
> + virt_to_phys(esi_buf), MAX_BUF_SZ);
It is good that you are passing a character buffer here and
interpreting it later. This helps in the cases where the header has
more fields than what we are aware of changed. I think even a future
platform adds newer fields to the header, those fields will be
appended after the existing fields, so we should still be able to
interpret the first three fields of the header that we are currently
aware of.
> + if (ret != H_SUCCESS) {
> + pr_warn("hcall failed: H_GET_ENERGY_SCALE_INFO");
> + goto out;
> + }
> +
> + esi_hdr = (struct h_energy_scale_info_hdr *) esi_buf;
> + num_attrs = be64_to_cpu(esi_hdr->num_attrs);
Shouldn't we check for the esi_hdr->data_header_version here?
Currently we are only aware of the version 1. If we happen to run this
kernel code on a future platform which supports a different version,
wouldn't it be safer to bail out here ?
Otherwise this patch looks good to me.
Reviewed-by: Gautham R. Shenoy <[email protected]>
--
Thanks and Regards
gautham.
On 08/07/21 4:05 pm, Gautham R Shenoy wrote:
> Hello Pratik,
>
> On Tue, Jul 06, 2021 at 01:54:00PM +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)
>> ...
>
> I like this implementation. Only one comment w.r.t versioning below:
>
> [..snip..]
>
>> @@ -631,6 +632,26 @@ struct hv_gpci_request_buffer {
>> uint8_t bytes[HGPCI_MAX_DATA_BYTES];
>> } __packed;
>>
>> +#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;
>> +
>
> [..snip..]
>
>> +static int __init papr_init(void)
>> +{
>> + uint64_t num_attrs;
>> + int ret, idx, i;
>> + char *esi_buf;
>> +
>> + if (!firmware_has_feature(FW_FEATURE_LPAR))
>> + return -ENXIO;
>> +
>> + esi_buf = kmalloc(MAX_BUF_SZ, GFP_KERNEL);
>> + if (esi_buf == NULL)
>> + return -ENOMEM;
>> + /*
>> + * 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
>> + */
>> + ret = plpar_hcall_norets(H_GET_ENERGY_SCALE_INFO, ESI_FLAGS_ALL, 0,
>> + virt_to_phys(esi_buf), MAX_BUF_SZ);
>
> It is good that you are passing a character buffer here and
> interpreting it later. This helps in the cases where the header has
> more fields than what we are aware of changed. I think even a future
> platform adds newer fields to the header, those fields will be
> appended after the existing fields, so we should still be able to
> interpret the first three fields of the header that we are currently
> aware of.
>
>
>> + if (ret != H_SUCCESS) {
>> + pr_warn("hcall failed: H_GET_ENERGY_SCALE_INFO");
>> + goto out;
>> + }
>> +
>> + esi_hdr = (struct h_energy_scale_info_hdr *) esi_buf;
>> + num_attrs = be64_to_cpu(esi_hdr->num_attrs);
>
> Shouldn't we check for the esi_hdr->data_header_version here?
> Currently we are only aware of the version 1. If we happen to run this
> kernel code on a future platform which supports a different version,
> wouldn't it be safer to bail out here ?
>
> Otherwise this patch looks good to me.
>
> Reviewed-by: Gautham R. Shenoy <[email protected]>
Thanks for the review Gautham.
Sure I'll make use of the header version to bail out.
That just seems like the safest approach.
I'll add that and spin a new version here
Thanks
Pratik
> --
> Thanks and Regards
> gautham.