[PATCH v8 1/2] powerpc/pseries: Interface to represent PAPR firmware attributes
Pratik Sampat
psampat at linux.ibm.com
Tue Sep 28 22:43:18 AEST 2021
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 at linux.ibm.com>
>> Reviewed-by: Gautham R. Shenoy <ego at linux.vnet.ibm.com>
>> Reviewed-by: Fabiano Rosas <farosas at linux.ibm.com>
>> Reviewed-by: Kajol Jain <kjain at linux.ibm.com>
>> ---
>> .../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 at ozlabs.org>
>> +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 at ozlabs.org>
>> +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
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