From 27600805e62f800bacf990354632eae4e487d34c Mon Sep 17 00:00:00 2001
From: Yazen Ghannam <yazen.ghannam@amd.com>
Date: Thu, 3 Sep 2026 10:43:25 -0500
Subject: x86/amd_node: Fix PCI device reference counting in amd_smn_init()

The local "root" pointer is a temporary variable used during the device
search. Therefore, refcount related to the search iterators should be cleaned
up after the search is complete.

Use the __free() cleanup macro to ensure the refcount is decremented when the
temporary pointer goes out of scope.

Additionally, increment the refcount when caching a root pointer. This ensures
the in-use refcount is separate from the temporary search refcounting.

Finally, drop the redundant "root = NULL" before the second search loop. The
pci_get_class() iterator always decrements the refcount of its "from"
argument, so the first loop can only fall through with "root" already NULL.

Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching")
Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com
Reported-by: Sashiko <sashiko-bot@kernel.org>
Assisted-by: LLM
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com
---
 samples/bpf/hbm.c | 515 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 515 insertions(+)
 create mode 100644 samples/bpf/hbm.c

(limited to 'samples/bpf/hbm.c')

diff --git a/samples/bpf/hbm.c b/samples/bpf/hbm.c
new file mode 100644
index 000000000..fc88d4dbd
--- /dev/null
+++ b/samples/bpf/hbm.c
@@ -0,0 +1,515 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2019 Facebook
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * Example program for Host Bandwidth Management
+ *
+ * This program loads a cgroup skb BPF program to enforce cgroup output
+ * (egress) or input (ingress) bandwidth limits.
+ *
+ * USAGE: hbm [-d] [-l] [-n <id>] [-r <rate>] [-s] [-t <secs>] [-w] [-h] [prog]
+ *   Where:
+ *    -d	Print BPF trace debug buffer
+ *    -l	Also limit flows doing loopback
+ *    -n <#>	To create cgroup \"/hbm#\" and attach prog
+ *		Default is /hbm1
+ *    --no_cn   Do not return cn notifications
+ *    -r <rate>	Rate limit in Mbps
+ *    -s	Get HBM stats (marked, dropped, etc.)
+ *    -t <time>	Exit after specified seconds (default is 0)
+ *    -w	Work conserving flag. cgroup can increase its bandwidth
+ *		beyond the rate limit specified while there is available
+ *		bandwidth. Current implementation assumes there is only
+ *		NIC (eth0), but can be extended to support multiple NICs.
+ *		Currently only supported for egress.
+ *    -h	Print this info
+ *    prog	BPF program file name. Name defaults to hbm_out_kern.o
+ */
+
+#define _GNU_SOURCE
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include <sys/time.h>
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/unistd.h>
+#include <linux/compiler.h>
+
+#include <linux/bpf.h>
+#include <bpf/bpf.h>
+#include <getopt.h>
+
+#include "cgroup_helpers.h"
+#include "hbm.h"
+#include "bpf_util.h"
+#include <bpf/libbpf.h>
+
+bool outFlag = true;
+int minRate = 1000;		/* cgroup rate limit in Mbps */
+int rate = 1000;		/* can grow if rate conserving is enabled */
+int dur = 1;
+bool stats_flag;
+bool loopback_flag;
+bool debugFlag;
+bool work_conserving_flag;
+bool no_cn_flag;
+bool edt_flag;
+
+static void Usage(void);
+static void read_trace_pipe2(void);
+static void do_error(char *msg, bool errno_flag);
+
+#define TRACEFS "/sys/kernel/tracing/"
+
+static struct bpf_program *bpf_prog;
+static struct bpf_object *obj;
+static int queue_stats_fd;
+
+static void read_trace_pipe2(void)
+{
+	int trace_fd;
+	FILE *outf;
+	char *outFname = "hbm_out.log";
+
+	trace_fd = open(TRACEFS "trace_pipe", O_RDONLY, 0);
+	if (trace_fd < 0) {
+		printf("Error opening trace_pipe\n");
+		return;
+	}
+
+//	Future support of ingress
+//	if (!outFlag)
+//		outFname = "hbm_in.log";
+	outf = fopen(outFname, "w");
+
+	if (outf == NULL)
+		printf("Error creating %s\n", outFname);
+
+	while (1) {
+		static char buf[4097];
+		ssize_t sz;
+
+		sz = read(trace_fd, buf, sizeof(buf) - 1);
+		if (sz > 0) {
+			buf[sz] = 0;
+			puts(buf);
+			if (outf != NULL) {
+				fprintf(outf, "%s\n", buf);
+				fflush(outf);
+			}
+		}
+	}
+}
+
+static void do_error(char *msg, bool errno_flag)
+{
+	if (errno_flag)
+		printf("ERROR: %s, errno: %d\n", msg, errno);
+	else
+		printf("ERROR: %s\n", msg);
+	exit(1);
+}
+
+static int prog_load(char *prog)
+{
+	struct bpf_program *pos;
+	const char *sec_name;
+
+	obj = bpf_object__open_file(prog, NULL);
+	if (libbpf_get_error(obj)) {
+		printf("ERROR: opening BPF object file failed\n");
+		return 1;
+	}
+
+	/* load BPF program */
+	if (bpf_object__load(obj)) {
+		printf("ERROR: loading BPF object file failed\n");
+		goto err;
+	}
+
+	bpf_object__for_each_program(pos, obj) {
+		sec_name = bpf_program__section_name(pos);
+		if (sec_name && !strcmp(sec_name, "cgroup_skb/egress")) {
+			bpf_prog = pos;
+			break;
+		}
+	}
+	if (!bpf_prog) {
+		printf("ERROR: finding a prog in obj file failed\n");
+		goto err;
+	}
+
+	queue_stats_fd = bpf_object__find_map_fd_by_name(obj, "queue_stats");
+	if (queue_stats_fd < 0) {
+		printf("ERROR: finding a map in obj file failed\n");
+		goto err;
+	}
+
+	return 0;
+
+err:
+	bpf_object__close(obj);
+	return 1;
+}
+
+static int run_bpf_prog(char *prog, int cg_id)
+{
+	struct hbm_queue_stats qstats = {0};
+	char cg_dir[100], cg_pin_path[100];
+	struct bpf_link *link = NULL;
+	int key = 0;
+	int cg1 = 0;
+	int rc = 0;
+
+	sprintf(cg_dir, "/hbm%d", cg_id);
+	rc = prog_load(prog);
+	if (rc != 0)
+		return rc;
+
+	if (setup_cgroup_environment()) {
+		printf("ERROR: setting cgroup environment\n");
+		goto err;
+	}
+	cg1 = create_and_get_cgroup(cg_dir);
+	if (!cg1) {
+		printf("ERROR: create_and_get_cgroup\n");
+		goto err;
+	}
+	if (join_cgroup(cg_dir)) {
+		printf("ERROR: join_cgroup\n");
+		goto err;
+	}
+
+	qstats.rate = rate;
+	qstats.stats = stats_flag ? 1 : 0;
+	qstats.loopback = loopback_flag ? 1 : 0;
+	qstats.no_cn = no_cn_flag ? 1 : 0;
+	if (bpf_map_update_elem(queue_stats_fd, &key, &qstats, BPF_ANY)) {
+		printf("ERROR: Could not update map element\n");
+		goto err;
+	}
+
+	if (!outFlag)
+		bpf_program__set_expected_attach_type(bpf_prog, BPF_CGROUP_INET_INGRESS);
+
+	link = bpf_program__attach_cgroup(bpf_prog, cg1);
+	if (libbpf_get_error(link)) {
+		fprintf(stderr, "ERROR: bpf_program__attach_cgroup failed\n");
+		goto err;
+	}
+
+	sprintf(cg_pin_path, "/sys/fs/bpf/hbm%d", cg_id);
+	rc = bpf_link__pin(link, cg_pin_path);
+	if (rc < 0) {
+		printf("ERROR: bpf_link__pin failed: %d\n", rc);
+		goto err;
+	}
+
+	if (work_conserving_flag) {
+		struct timeval t0, t_last, t_new;
+		FILE *fin;
+		unsigned long long last_eth_tx_bytes, new_eth_tx_bytes;
+		signed long long last_cg_tx_bytes, new_cg_tx_bytes;
+		signed long long delta_time, delta_bytes, delta_rate;
+		int delta_ms;
+#define DELTA_RATE_CHECK 10000		/* in us */
+#define RATE_THRESHOLD 9500000000	/* 9.5 Gbps */
+
+		bpf_map_lookup_elem(queue_stats_fd, &key, &qstats);
+		if (gettimeofday(&t0, NULL) < 0)
+			do_error("gettimeofday failed", true);
+		t_last = t0;
+		fin = fopen("/sys/class/net/eth0/statistics/tx_bytes", "r");
+		if (fscanf(fin, "%llu", &last_eth_tx_bytes) != 1)
+			do_error("fscanf fails", false);
+		fclose(fin);
+		last_cg_tx_bytes = qstats.bytes_total;
+		while (true) {
+			usleep(DELTA_RATE_CHECK);
+			if (gettimeofday(&t_new, NULL) < 0)
+				do_error("gettimeofday failed", true);
+			delta_ms = (t_new.tv_sec - t0.tv_sec) * 1000 +
+				(t_new.tv_usec - t0.tv_usec)/1000;
+			if (delta_ms > dur * 1000)
+				break;
+			delta_time = (t_new.tv_sec - t_last.tv_sec) * 1000000 +
+				(t_new.tv_usec - t_last.tv_usec);
+			if (delta_time == 0)
+				continue;
+			t_last = t_new;
+			fin = fopen("/sys/class/net/eth0/statistics/tx_bytes",
+				    "r");
+			if (fscanf(fin, "%llu", &new_eth_tx_bytes) != 1)
+				do_error("fscanf fails", false);
+			fclose(fin);
+			printf("  new_eth_tx_bytes:%llu\n",
+			       new_eth_tx_bytes);
+			bpf_map_lookup_elem(queue_stats_fd, &key, &qstats);
+			new_cg_tx_bytes = qstats.bytes_total;
+			delta_bytes = new_eth_tx_bytes - last_eth_tx_bytes;
+			last_eth_tx_bytes = new_eth_tx_bytes;
+			delta_rate = (delta_bytes * 8000000) / delta_time;
+			printf("%5d - eth_rate:%.1fGbps cg_rate:%.3fGbps",
+			       delta_ms, delta_rate/1000000000.0,
+			       rate/1000.0);
+			if (delta_rate < RATE_THRESHOLD) {
+				/* can increase cgroup rate limit, but first
+				 * check if we are using the current limit.
+				 * Currently increasing by 6.25%, unknown
+				 * if that is the optimal rate.
+				 */
+				int rate_diff100;
+
+				delta_bytes = new_cg_tx_bytes -
+					last_cg_tx_bytes;
+				last_cg_tx_bytes = new_cg_tx_bytes;
+				delta_rate = (delta_bytes * 8000000) /
+					delta_time;
+				printf(" rate:%.3fGbps",
+				       delta_rate/1000000000.0);
+				rate_diff100 = (((long long)rate)*1000000 -
+						     delta_rate) * 100 /
+					(((long long) rate) * 1000000);
+				printf("  rdiff:%d", rate_diff100);
+				if (rate_diff100  <= 3) {
+					rate += (rate >> 4);
+					if (rate > RATE_THRESHOLD / 1000000)
+						rate = RATE_THRESHOLD / 1000000;
+					qstats.rate = rate;
+					printf(" INC\n");
+				} else {
+					printf("\n");
+				}
+			} else {
+				/* Need to decrease cgroup rate limit.
+				 * Currently decreasing by 12.5%, unknown
+				 * if that is optimal
+				 */
+				printf(" DEC\n");
+				rate -= (rate >> 3);
+				if (rate < minRate)
+					rate = minRate;
+				qstats.rate = rate;
+			}
+			if (bpf_map_update_elem(queue_stats_fd, &key, &qstats, BPF_ANY))
+				do_error("update map element fails", false);
+		}
+	} else {
+		sleep(dur);
+	}
+	// Get stats!
+	if (stats_flag && bpf_map_lookup_elem(queue_stats_fd, &key, &qstats)) {
+		char fname[100];
+		FILE *fout;
+
+		if (!outFlag)
+			sprintf(fname, "hbm.%d.in", cg_id);
+		else
+			sprintf(fname, "hbm.%d.out", cg_id);
+		fout = fopen(fname, "w");
+		fprintf(fout, "id:%d\n", cg_id);
+		fprintf(fout, "ERROR: Could not lookup queue_stats\n");
+		fclose(fout);
+	} else if (stats_flag && qstats.lastPacketTime >
+		   qstats.firstPacketTime) {
+		long long delta_us = (qstats.lastPacketTime -
+				      qstats.firstPacketTime)/1000;
+		unsigned int rate_mbps = ((qstats.bytes_total -
+					   qstats.bytes_dropped) * 8 /
+					  delta_us);
+		double percent_pkts, percent_bytes;
+		char fname[100];
+		FILE *fout;
+		int k;
+		static const char *returnValNames[] = {
+			"DROP_PKT",
+			"ALLOW_PKT",
+			"DROP_PKT_CWR",
+			"ALLOW_PKT_CWR"
+		};
+#define RET_VAL_COUNT 4
+
+// Future support of ingress
+//		if (!outFlag)
+//			sprintf(fname, "hbm.%d.in", cg_id);
+//		else
+		sprintf(fname, "hbm.%d.out", cg_id);
+		fout = fopen(fname, "w");
+		fprintf(fout, "id:%d\n", cg_id);
+		fprintf(fout, "rate_mbps:%d\n", rate_mbps);
+		fprintf(fout, "duration:%.1f secs\n",
+			(qstats.lastPacketTime - qstats.firstPacketTime) /
+			1000000000.0);
+		fprintf(fout, "packets:%d\n", (int)qstats.pkts_total);
+		fprintf(fout, "bytes_MB:%d\n", (int)(qstats.bytes_total /
+						     1000000));
+		fprintf(fout, "pkts_dropped:%d\n", (int)qstats.pkts_dropped);
+		fprintf(fout, "bytes_dropped_MB:%d\n",
+			(int)(qstats.bytes_dropped /
+						       1000000));
+		// Marked Pkts and Bytes
+		percent_pkts = (qstats.pkts_marked * 100.0) /
+			(qstats.pkts_total + 1);
+		percent_bytes = (qstats.bytes_marked * 100.0) /
+			(qstats.bytes_total + 1);
+		fprintf(fout, "pkts_marked_percent:%6.2f\n", percent_pkts);
+		fprintf(fout, "bytes_marked_percent:%6.2f\n", percent_bytes);
+
+		// Dropped Pkts and Bytes
+		percent_pkts = (qstats.pkts_dropped * 100.0) /
+			(qstats.pkts_total + 1);
+		percent_bytes = (qstats.bytes_dropped * 100.0) /
+			(qstats.bytes_total + 1);
+		fprintf(fout, "pkts_dropped_percent:%6.2f\n", percent_pkts);
+		fprintf(fout, "bytes_dropped_percent:%6.2f\n", percent_bytes);
+
+		// ECN CE markings
+		percent_pkts = (qstats.pkts_ecn_ce * 100.0) /
+			(qstats.pkts_total + 1);
+		fprintf(fout, "pkts_ecn_ce:%6.2f (%d)\n", percent_pkts,
+			(int)qstats.pkts_ecn_ce);
+
+		// Average cwnd
+		fprintf(fout, "avg cwnd:%d\n",
+			(int)(qstats.sum_cwnd / (qstats.sum_cwnd_cnt + 1)));
+		// Average rtt
+		fprintf(fout, "avg rtt:%d\n",
+			(int)(qstats.sum_rtt / (qstats.pkts_total + 1)));
+		// Average credit
+		if (edt_flag)
+			fprintf(fout, "avg credit_ms:%.03f\n",
+				(qstats.sum_credit /
+				 (qstats.pkts_total + 1.0)) / 1000000.0);
+		else
+			fprintf(fout, "avg credit:%d\n",
+				(int)(qstats.sum_credit /
+				      (1500 * ((int)qstats.pkts_total ) + 1)));
+
+		// Return values stats
+		for (k = 0; k < RET_VAL_COUNT; k++) {
+			percent_pkts = (qstats.returnValCount[k] * 100.0) /
+				(qstats.pkts_total + 1);
+			fprintf(fout, "%s:%6.2f (%d)\n", returnValNames[k],
+				percent_pkts, (int)qstats.returnValCount[k]);
+		}
+		fclose(fout);
+	}
+
+	if (debugFlag)
+		read_trace_pipe2();
+	goto cleanup;
+
+err:
+	rc = 1;
+
+cleanup:
+	bpf_link__destroy(link);
+	bpf_object__close(obj);
+
+	if (cg1 != -1)
+		close(cg1);
+
+	if (rc != 0)
+		cleanup_cgroup_environment();
+	return rc;
+}
+
+static void Usage(void)
+{
+	printf("This program loads a cgroup skb BPF program to enforce\n"
+	       "cgroup output (egress) bandwidth limits.\n\n"
+	       "USAGE: hbm [-o] [-d]  [-l] [-n <id>] [--no_cn] [-r <rate>]\n"
+	       "           [-s] [-t <secs>] [-w] [-h] [prog]\n"
+	       "  Where:\n"
+	       "    -o         indicates egress direction (default)\n"
+	       "    -d         print BPF trace debug buffer\n"
+	       "    --edt      use fq's Earliest Departure Time\n"
+	       "    -l         also limit flows using loopback\n"
+	       "    -n <#>     to create cgroup \"/hbm#\" and attach prog\n"
+	       "               Default is /hbm1\n"
+	       "    --no_cn    disable CN notifications\n"
+	       "    -r <rate>  Rate in Mbps\n"
+	       "    -s         Update HBM stats\n"
+	       "    -t <time>  Exit after specified seconds (default is 0)\n"
+	       "    -w	       Work conserving flag. cgroup can increase\n"
+	       "               bandwidth beyond the rate limit specified\n"
+	       "               while there is available bandwidth. Current\n"
+	       "               implementation assumes there is only eth0\n"
+	       "               but can be extended to support multiple NICs\n"
+	       "    -h         print this info\n"
+	       "    prog       BPF program file name. Name defaults to\n"
+	       "                 hbm_out_kern.o\n");
+}
+
+int main(int argc, char **argv)
+{
+	char *prog = "hbm_out_kern.o";
+	int  k;
+	int cg_id = 1;
+	char *optstring = "iodln:r:st:wh";
+	struct option loptions[] = {
+		{"no_cn", 0, NULL, 1},
+		{"edt", 0, NULL, 2},
+		{NULL, 0, NULL, 0}
+	};
+
+	while ((k = getopt_long(argc, argv, optstring, loptions, NULL)) != -1) {
+		switch (k) {
+		case 1:
+			no_cn_flag = true;
+			break;
+		case 2:
+			prog = "hbm_edt_kern.o";
+			edt_flag = true;
+			break;
+		case'o':
+			break;
+		case 'd':
+			debugFlag = true;
+			break;
+		case 'l':
+			loopback_flag = true;
+			break;
+		case 'n':
+			cg_id = atoi(optarg);
+			break;
+		case 'r':
+			minRate = atoi(optarg) * 1.024;
+			rate = minRate;
+			break;
+		case 's':
+			stats_flag = true;
+			break;
+		case 't':
+			dur = atoi(optarg);
+			break;
+		case 'w':
+			work_conserving_flag = true;
+			break;
+		case '?':
+			if (optopt == 'n' || optopt == 'r' || optopt == 't')
+				fprintf(stderr,
+					"Option -%c requires an argument.\n\n",
+					optopt);
+		case 'h':
+		default:
+			Usage();
+			return 0;
+		}
+	}
+
+	if (optind < argc)
+		prog = argv[optind];
+	printf("HBM prog: %s\n", prog != NULL ? prog : "NULL");
+
+	/* Use libbpf 1.0 API mode */
+	libbpf_set_strict_mode(LIBBPF_STRICT_ALL);
+
+	return run_bpf_prog(prog, cg_id);
+}
-- 
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