KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 257 insertions, 0 deletions

diff --git a/drivers/hwmon/occ/sysfs.c b/drivers/hwmon/occ/sysfs.c
new file mode 100644
index 000000000..2317301fc
--- /dev/null
+++ b/drivers/hwmon/occ/sysfs.c
@@ -0,0 +1,257 @@
+// SPDX-License-Identifier: GPL-2.0+
+// Copyright IBM Corp 2019
+
+#include <linux/bitops.h>
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/kernel.h>
+#include <linux/kstrtox.h>
+#include <linux/sysfs.h>
+
+#include "common.h"
+
+/* OCC status register */
+#define OCC_STAT_MASTER			BIT(7)
+
+/* OCC extended status register */
+#define OCC_EXT_STAT_DVFS_OT		BIT(7)
+#define OCC_EXT_STAT_DVFS_POWER		BIT(6)
+#define OCC_EXT_STAT_MEM_THROTTLE	BIT(5)
+#define OCC_EXT_STAT_QUICK_DROP		BIT(4)
+#define OCC_EXT_STAT_DVFS_VDD		BIT(3)
+#define OCC_EXT_STAT_GPU_THROTTLE	GENMASK(2, 0)
+
+static ssize_t occ_active_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	int rc;
+	bool active;
+	struct occ *occ = dev_get_drvdata(dev);
+
+	rc = kstrtobool(buf, &active);
+	if (rc)
+		return rc;
+
+	rc = occ_active(occ, active);
+	if (rc)
+		return rc;
+
+	return count;
+}
+
+static ssize_t occ_sysfs_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	int rc;
+	int val = 0;
+	struct occ *occ = dev_get_drvdata(dev);
+	struct occ_poll_response_header *header;
+	struct sensor_device_attribute *sattr = to_sensor_dev_attr(attr);
+
+	if (occ->active) {
+		rc = occ_update_response(occ);
+		if (rc)
+			return rc;
+
+		header = (struct occ_poll_response_header *)occ->resp.data;
+
+		switch (sattr->index) {
+		case 0:
+			val = !!(header->status & OCC_STAT_MASTER);
+			break;
+		case 1:
+			val = 1;
+			break;
+		case 2:
+			val = !!(header->ext_status & OCC_EXT_STAT_DVFS_OT);
+			break;
+		case 3:
+			val = !!(header->ext_status & OCC_EXT_STAT_DVFS_POWER);
+			break;
+		case 4:
+			val = !!(header->ext_status &
+				 OCC_EXT_STAT_MEM_THROTTLE);
+			break;
+		case 5:
+			val = !!(header->ext_status & OCC_EXT_STAT_QUICK_DROP);
+			break;
+		case 6:
+			val = header->occ_state;
+			break;
+		case 7:
+			if (header->status & OCC_STAT_MASTER)
+				val = hweight8(header->occs_present);
+			else
+				val = 1;
+			break;
+		case 8:
+			val = header->ips_status;
+			break;
+		case 9:
+			val = header->mode;
+			break;
+		case 10:
+			val = !!(header->ext_status & OCC_EXT_STAT_DVFS_VDD);
+			break;
+		case 11:
+			val = header->ext_status & OCC_EXT_STAT_GPU_THROTTLE;
+			break;
+		default:
+			return -EINVAL;
+		}
+	} else {
+		if (sattr->index == 1)
+			val = 0;
+		else if (sattr->index <= 11)
+			val = -ENODATA;
+		else
+			return -EINVAL;
+	}
+
+	return sysfs_emit(buf, "%d\n", val);
+}
+
+static ssize_t occ_error_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	struct occ *occ = dev_get_drvdata(dev);
+
+	occ_update_response(occ);
+
+	return sysfs_emit(buf, "%d\n", occ->error);
+}
+
+static SENSOR_DEVICE_ATTR(occ_master, 0444, occ_sysfs_show, NULL, 0);
+static SENSOR_DEVICE_ATTR(occ_active, 0644, occ_sysfs_show, occ_active_store,
+			  1);
+static SENSOR_DEVICE_ATTR(occ_dvfs_overtemp, 0444, occ_sysfs_show, NULL, 2);
+static SENSOR_DEVICE_ATTR(occ_dvfs_power, 0444, occ_sysfs_show, NULL, 3);
+static SENSOR_DEVICE_ATTR(occ_mem_throttle, 0444, occ_sysfs_show, NULL, 4);
+static SENSOR_DEVICE_ATTR(occ_quick_pwr_drop, 0444, occ_sysfs_show, NULL, 5);
+static SENSOR_DEVICE_ATTR(occ_state, 0444, occ_sysfs_show, NULL, 6);
+static SENSOR_DEVICE_ATTR(occs_present, 0444, occ_sysfs_show, NULL, 7);
+static SENSOR_DEVICE_ATTR(occ_ips_status, 0444, occ_sysfs_show, NULL, 8);
+static SENSOR_DEVICE_ATTR(occ_mode, 0444, occ_sysfs_show, NULL, 9);
+static SENSOR_DEVICE_ATTR(occ_dvfs_vdd, 0444, occ_sysfs_show, NULL, 10);
+static SENSOR_DEVICE_ATTR(occ_gpu_throttle, 0444, occ_sysfs_show, NULL, 11);
+static DEVICE_ATTR_RO(occ_error);
+
+static struct attribute *occ_attributes[] = {
+	&sensor_dev_attr_occ_master.dev_attr.attr,
+	&sensor_dev_attr_occ_active.dev_attr.attr,
+	&sensor_dev_attr_occ_dvfs_overtemp.dev_attr.attr,
+	&sensor_dev_attr_occ_dvfs_power.dev_attr.attr,
+	&sensor_dev_attr_occ_mem_throttle.dev_attr.attr,
+	&sensor_dev_attr_occ_quick_pwr_drop.dev_attr.attr,
+	&sensor_dev_attr_occ_state.dev_attr.attr,
+	&sensor_dev_attr_occs_present.dev_attr.attr,
+	&sensor_dev_attr_occ_ips_status.dev_attr.attr,
+	&sensor_dev_attr_occ_mode.dev_attr.attr,
+	&sensor_dev_attr_occ_dvfs_vdd.dev_attr.attr,
+	&sensor_dev_attr_occ_gpu_throttle.dev_attr.attr,
+	&dev_attr_occ_error.attr,
+	NULL
+};
+
+static const struct attribute_group occ_sysfs = {
+	.attrs = occ_attributes,
+};
+
+void occ_sysfs_poll_done(struct occ *occ)
+{
+	const char *name;
+	struct occ_poll_response_header *header =
+		(struct occ_poll_response_header *)occ->resp.data;
+
+	/*
+	 * On the first poll response, we haven't yet created the sysfs
+	 * attributes, so don't make any notify calls.
+	 */
+	if (!occ->active)
+		goto done;
+
+	if ((header->status & OCC_STAT_MASTER) !=
+	    (occ->prev_stat & OCC_STAT_MASTER)) {
+		name = sensor_dev_attr_occ_master.dev_attr.attr.name;
+		sysfs_notify(&occ->bus_dev->kobj, NULL, name);
+	}
+
+	if ((header->ext_status & OCC_EXT_STAT_DVFS_OT) !=
+	    (occ->prev_ext_stat & OCC_EXT_STAT_DVFS_OT)) {
+		name = sensor_dev_attr_occ_dvfs_overtemp.dev_attr.attr.name;
+		sysfs_notify(&occ->bus_dev->kobj, NULL, name);
+	}
+
+	if ((header->ext_status & OCC_EXT_STAT_DVFS_POWER) !=
+	    (occ->prev_ext_stat & OCC_EXT_STAT_DVFS_POWER)) {
+		name = sensor_dev_attr_occ_dvfs_power.dev_attr.attr.name;
+		sysfs_notify(&occ->bus_dev->kobj, NULL, name);
+	}
+
+	if ((header->ext_status & OCC_EXT_STAT_MEM_THROTTLE) !=
+	    (occ->prev_ext_stat & OCC_EXT_STAT_MEM_THROTTLE)) {
+		name = sensor_dev_attr_occ_mem_throttle.dev_attr.attr.name;
+		sysfs_notify(&occ->bus_dev->kobj, NULL, name);
+	}
+
+	if ((header->ext_status & OCC_EXT_STAT_QUICK_DROP) !=
+	    (occ->prev_ext_stat & OCC_EXT_STAT_QUICK_DROP)) {
+		name = sensor_dev_attr_occ_quick_pwr_drop.dev_attr.attr.name;
+		sysfs_notify(&occ->bus_dev->kobj, NULL, name);
+	}
+
+	if ((header->ext_status & OCC_EXT_STAT_DVFS_VDD) !=
+	    (occ->prev_ext_stat & OCC_EXT_STAT_DVFS_VDD)) {
+		name = sensor_dev_attr_occ_dvfs_vdd.dev_attr.attr.name;
+		sysfs_notify(&occ->bus_dev->kobj, NULL, name);
+	}
+
+	if ((header->ext_status & OCC_EXT_STAT_GPU_THROTTLE) !=
+	    (occ->prev_ext_stat & OCC_EXT_STAT_GPU_THROTTLE)) {
+		name = sensor_dev_attr_occ_gpu_throttle.dev_attr.attr.name;
+		sysfs_notify(&occ->bus_dev->kobj, NULL, name);
+	}
+
+	if ((header->status & OCC_STAT_MASTER) &&
+	    header->occs_present != occ->prev_occs_present) {
+		name = sensor_dev_attr_occs_present.dev_attr.attr.name;
+		sysfs_notify(&occ->bus_dev->kobj, NULL, name);
+	}
+
+	if (header->ips_status != occ->prev_ips_status) {
+		name = sensor_dev_attr_occ_ips_status.dev_attr.attr.name;
+		sysfs_notify(&occ->bus_dev->kobj, NULL, name);
+	}
+
+	if (header->mode != occ->prev_mode) {
+		name = sensor_dev_attr_occ_mode.dev_attr.attr.name;
+		sysfs_notify(&occ->bus_dev->kobj, NULL, name);
+	}
+
+	if (occ->error && occ->error != occ->prev_error) {
+		name = dev_attr_occ_error.attr.name;
+		sysfs_notify(&occ->bus_dev->kobj, NULL, name);
+	}
+
+	/* no notifications for OCC state; doesn't indicate error condition */
+
+done:
+	occ->prev_error = occ->error;
+	occ->prev_stat = header->status;
+	occ->prev_ext_stat = header->ext_status;
+	occ->prev_occs_present = header->occs_present;
+	occ->prev_ips_status = header->ips_status;
+	occ->prev_mode = header->mode;
+}
+
+int occ_setup_sysfs(struct occ *occ)
+{
+	return sysfs_create_group(&occ->bus_dev->kobj, &occ_sysfs);
+}
+
+void occ_shutdown_sysfs(struct occ *occ)
+{
+	sysfs_remove_group(&occ->bus_dev->kobj, &occ_sysfs);
+}