[RFC PATCH v7 7/7] x86/mm/ibs: In-kernel driver for AMD IBS Memory Profiler

[Bharata B Rao]

Use IBS (Instruction Based Sampling) Memory Profiler feature
present in AMD Zen6 processors for memory access tracking. The
access information obtained from IBS Memory Profiler is fed to
pghot sub-system for further action using
pghot_record_access(PGHOT_HWHINTS, ...) API.

IBS Memory Profiler as page hotness source is enabled by the
new config option HWMEM_PROFILER and is also gated by the
existing pghot_src_hwhints static key set via debugfs.

More details about IBS Memory Profiler can be obtained from
the AMD document titled "AMD64 Zen6 Instruction Based Sampling (IBS)
Extensions and Features".

Signed-off-by: Bharata B Rao <bharata@xxxxxxx>
---
 arch/x86/Kconfig                 |  16 ++
 arch/x86/include/asm/ibs-caps.h  |   8 +
 arch/x86/include/asm/ibs-mprof.h |  46 +++++
 arch/x86/include/asm/msr-index.h |   8 +
 arch/x86/mm/Makefile             |   1 +
 arch/x86/mm/ibs-mprof.c          | 308 +++++++++++++++++++++++++++++++
 include/linux/cpuhotplug.h       |   1 +
 include/linux/vm_event_item.h    |   6 +
 mm/Kconfig                       |   9 +
 mm/vmstat.c                      |   6 +
 10 files changed, 409 insertions(+)
 create mode 100644 arch/x86/include/asm/ibs-mprof.h
 create mode 100644 arch/x86/mm/ibs-mprof.c

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 99bb5217649a..f06c0c44ecce 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1514,6 +1514,22 @@ config AMD_MEM_ENCRYPT
 	  This requires an AMD processor that supports Secure Memory
 	  Encryption (SME).
 
+config AMD_IBS_MEMPROF
+	bool "AMD IBS Memory Profiler"
+	depends on X86_64 && CPU_SUP_AMD
+	depends on PGHOT
+	select HWMEM_PROFILER
+	help
+	  Use the AMD Instruction Based Sampling (IBS) Memory Profiler
+	  facility (present on Zen6 and later AMD CPUs) to feed
+	  hardware-observed memory accesses into the pghot subsystem
+	  for hot-page detection and promotion.
+
+	  When disabled, no IBS Memory Profiler MSRs are programmed and
+	  the corresponding NMI handler is not installed.
+
+	  If unsure, say N.
+
 # Common NUMA Features
 config NUMA
 	bool "NUMA Memory Allocation and Scheduler Support"
diff --git a/arch/x86/include/asm/ibs-caps.h b/arch/x86/include/asm/ibs-caps.h
index ddf6c512c8f9..1f6c4058a0e3 100644
--- a/arch/x86/include/asm/ibs-caps.h
+++ b/arch/x86/include/asm/ibs-caps.h
@@ -29,6 +29,7 @@
 #define IBS_CAPS_FETCHLAT		(1U<<14)
 #define IBS_CAPS_BIT63_FILTER		(1U<<15)
 #define IBS_CAPS_STRMST_RMTSOCKET	(1U<<16)
+#define IBS_CAPS_MEM_PROFILER		(1U<<18)
 #define IBS_CAPS_OPDTLBPGSIZE		(1U<<19)
 
 #define IBS_CAPS_DEFAULT		(IBS_CAPS_AVAIL		\
@@ -42,6 +43,13 @@
 #define IBSCTL_LVT_OFFSET_VALID		(1ULL<<8)
 #define IBSCTL_LVT_OFFSET_MASK		0x0F
 
+/*
+ * IBS Memprofiler setup
+ */
+#define IBSCTL_MPROF_LVT_OFFSET_VALID	(1ULL << 24)
+#define IBSCTL_MPROF_LVT_OFFSET_SHIFT	16
+#define IBSCTL_MPROF_LVT_OFFSET_MASK	(0xFULL << IBSCTL_MPROF_LVT_OFFSET_SHIFT)
+
 /* IBS fetch bits/masks */
 #define IBS_FETCH_L3MISSONLY		      (1ULL << 59)
 #define IBS_FETCH_RAND_EN		      (1ULL << 57)
diff --git a/arch/x86/include/asm/ibs-mprof.h b/arch/x86/include/asm/ibs-mprof.h
new file mode 100644
index 000000000000..91b1ce51d667
--- /dev/null
+++ b/arch/x86/include/asm/ibs-mprof.h
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_IBS_MPROF_H
+#define _ASM_X86_IBS_MPROF_H
+
+/*
+ * All bits are documented here for clarity even if the current
+ * driver doesn't use all of them.
+ */
+
+/* MSR_AMD64_IBS_MPROF_DATA2 bits */
+#define IBS_MPROF_DATA2_DATASRC_MASK		0x7
+#define IBS_MPROF_DATA2_DATASRC_MASK_HIGH	0xC0
+#define IBS_MPROF_DATA2_DATASRC_MASK_HIGH_SHIFT	0x3
+#define IBS_MPROF_DATA2_DATASRC_LCL_CCX		0x1
+#define IBS_MPROF_DATA2_DATASRC_PEER_CCX_NEAR	0x2
+#define IBS_MPROF_DATA2_DATASRC_DRAM		0x3
+#define IBS_MPROF_DATA2_DATASRC_CCX_FAR		0x5
+#define IBS_MPROF_DATA2_DATASRC_EXT_MEM		0x8
+#define IBS_MPROF_DATA2_RMT_NODE		BIT_ULL(4)
+#define IBS_MPROF_DATA2_RMT_SOCKET		BIT_ULL(9)
+
+/* MSR_AMD64_IBS_MPROF_DATA3 bits */
+#define IBS_MPROF_DATA3_LDOP		BIT_ULL(0)
+#define IBS_MPROF_DATA3_STOP		BIT_ULL(1)
+#define IBS_MPROF_DATA3_DCMISS		BIT_ULL(7)
+#define IBS_MPROF_DATA3_LADDR_VALID	BIT_ULL(17)
+#define IBS_MPROF_DATA3_PADDR_VALID	BIT_ULL(18)
+#define IBS_MPROF_DATA3_L2MISS		BIT_ULL(20)
+#define IBS_MPROF_DATA3_SW_PREFETCH	BIT_ULL(21)
+
+/* MSR_AMD64_IBS_MPROF_CTL bits */
+#define IBS_MPROF_CTL_CNT_CTL		BIT_ULL(19)
+#define IBS_MPROF_CTL_VAL		BIT_ULL(18)
+#define IBS_MPROF_CTL_ENABLE		BIT_ULL(17)
+#define IBS_MPROF_CTL_L3MISSONLY	BIT_ULL(16)
+#define IBS_MPROF_CTL_MAXCNT_MASK	0x0000FFFFULL
+#define IBS_MPROF_CTL_MAXCNT_EXT_MASK	(0x7FULL << 20)	/* separate upper 7 bits */
+
+/* MSR_AMD64_IBS_MPROF_CTL2 bits */
+#define IBS_MPROF_CTL2_DISABLE		BIT_ULL(0)
+#define IBS_MPROF_CTL2_EXCLUDE_USER	BIT_ULL(1)
+#define IBS_MPROF_CTL2_EXCLUDE_KERNEL	BIT_ULL(2)
+
+#define IBS_MPROF_SAMPLE_PERIOD	10000
+
+#endif /* _ASM_X86_IBS_MPROF_H */
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index a14a0f43e04a..c44b68940f43 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -1315,4 +1315,12 @@
 						* a #GP
 						*/
 
+/* AMD IBS Memory Profiler MSRs */
+#define MSR_AMD64_IBS_MPROF_CTL		0xc0010380
+#define MSR_AMD64_IBS_MPROF_CTL2	0xc0010381
+#define MSR_AMD64_IBS_MPROF_DATA2	0xc0010382
+#define MSR_AMD64_IBS_MPROF_DATA3	0xc0010383
+#define MSR_AMD64_IBS_MPROF_LINADDR	0xc0010384
+#define MSR_AMD64_IBS_MPROF_PHYADDR	0xc0010385
+
 #endif /* _ASM_X86_MSR_INDEX_H */
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index 3a5364853eab..050a7379d9f7 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -59,3 +59,4 @@ obj-$(CONFIG_X86_MEM_ENCRYPT)	+= mem_encrypt.o
 obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt_amd.o
 
 obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt_boot.o
+obj-$(CONFIG_AMD_IBS_MEMPROF)	+= ibs-mprof.o
diff --git a/arch/x86/mm/ibs-mprof.c b/arch/x86/mm/ibs-mprof.c
new file mode 100644
index 000000000000..b3d59b21c8c9
--- /dev/null
+++ b/arch/x86/mm/ibs-mprof.c
@@ -0,0 +1,308 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define pr_fmt(fmt)	"amd_ibs_memprof: " fmt
+
+#include <linux/init.h>
+#include <linux/pghot.h>
+#include <linux/percpu.h>
+#include <linux/workqueue.h>
+#include <linux/irq_work.h>
+#include <linux/mm.h>
+#include <linux/vm_event_item.h>
+#include <linux/vmstat.h>
+#include <linux/cpuhotplug.h>
+
+#include <asm/ibs-mprof.h>
+#include <asm/ibs-caps.h>
+#include <asm/nmi.h>
+#include <asm/apic.h>
+
+#define IBS_NR_SAMPLES		150	/* Percpu sample buffer size */
+
+static DEFINE_PER_CPU(bool, mprof_work_pending);
+
+/*
+ * Basic access info captured for each memory access.
+ */
+struct mprof_sample {
+	unsigned long pfn;
+	unsigned long time;	/* jiffies when accessed */
+	int nid;		/* Accessing node ID, if known */
+};
+
+/*
+ * Percpu buffer of access samples. Samples are accumulated here
+ * before pushing them to pghot sub-system for further action.
+ */
+struct mprof_sample_pcpu {
+	struct mprof_sample samples[IBS_NR_SAMPLES];
+	int head, tail;
+};
+
+static struct mprof_sample_pcpu __percpu *mprof_s;
+
+/*
+ * The workqueue for pushing the percpu access samples to pghot sub-system.
+ */
+static DEFINE_PER_CPU(struct work_struct, mprof_work);
+static DEFINE_PER_CPU(struct irq_work, mprof_irq_work);
+
+/*
+ * Record the IBS-reported access sample in percpu buffer.
+ * Called from IBS NMI handler.
+ */
+static bool mprof_push_sample(unsigned long pfn, int nid, unsigned long time)
+{
+	struct mprof_sample_pcpu *pcpu = raw_cpu_ptr(mprof_s);
+	int head = READ_ONCE(pcpu->head);
+	int tail = READ_ONCE(pcpu->tail);
+	int next = head + 1;
+
+	if (next >= IBS_NR_SAMPLES)
+		next = 0;
+
+	if (next == tail)
+		return false;
+
+	pcpu->samples[head].pfn = pfn;
+	pcpu->samples[head].time = time;
+	pcpu->samples[head].nid = nid;
+
+	smp_store_release(&pcpu->head, next);
+	return true;
+}
+
+static bool mprof_pop_sample(struct mprof_sample *s)
+{
+	struct mprof_sample_pcpu *pcpu = raw_cpu_ptr(mprof_s);
+	int tail = READ_ONCE(pcpu->tail);
+	int head = smp_load_acquire(&pcpu->head);
+	int next = tail + 1;
+
+	if (head == tail)
+		return false;
+
+	if (next >= IBS_NR_SAMPLES)
+		next = 0;
+
+	*s = pcpu->samples[tail];
+
+	WRITE_ONCE(pcpu->tail, next);
+	return true;
+}
+
+/*
+ * Remove access samples from percpu buffer and send them
+ * to pghot sub-system for further action.
+ */
+static void mprof_work_handler(struct work_struct *work)
+{
+	struct mprof_sample s;
+
+	while (mprof_pop_sample(&s))
+		pghot_record_access(s.pfn, s.nid, PGHOT_HWHINTS, s.time);
+
+	this_cpu_write(mprof_work_pending, false);
+}
+
+static void mprof_irq_handler(struct irq_work *i)
+{
+	struct work_struct *w = this_cpu_ptr(&mprof_work);
+
+	/*
+	 * FIXME: pending samples on a CPU that goes offline before the
+	 * work runs may be lost or migrated to the wrong CPU's ring;
+	 * needs a teardown-time drain.
+	 */
+	schedule_work_on(smp_processor_id(), w);
+}
+
+/*
+ * L3MissOnly + Exclude kernel RIP
+ */
+static void mprof_enable_profiling(void)
+{
+	u64 mprof_config = IBS_MPROF_CTL_CNT_CTL | IBS_MPROF_CTL_ENABLE |
+			   IBS_MPROF_CTL_L3MISSONLY;
+	unsigned int period = IBS_MPROF_SAMPLE_PERIOD;
+	u64 ctl, ctl2;
+
+	/*
+	 * Assemble bits 26:20 and 19:4 of periodic op counter in ctl.
+	 * The lower 4 bits are always 0000b.
+	 */
+	ctl = (period >> 4) & IBS_MPROF_CTL_MAXCNT_MASK;
+	ctl |= (period & IBS_MPROF_CTL_MAXCNT_EXT_MASK);
+	ctl |= mprof_config;
+	wrmsrq(MSR_AMD64_IBS_MPROF_CTL, ctl);
+
+	/*
+	 * Exclude samples that have bit 63 of their RIP set.
+	 */
+	ctl2 = IBS_MPROF_CTL2_EXCLUDE_KERNEL;
+	wrmsrq(MSR_AMD64_IBS_MPROF_CTL2, ctl2);
+}
+
+static void mprof_disable_profiling(u64 mem_ctl)
+{
+	mem_ctl &= ~IBS_MPROF_CTL_ENABLE;
+	mem_ctl &= ~IBS_MPROF_CTL_VAL;
+	wrmsrq(MSR_AMD64_IBS_MPROF_CTL, mem_ctl);
+
+	wrmsrq(MSR_AMD64_IBS_MPROF_CTL2, IBS_MPROF_CTL2_DISABLE);
+}
+
+/*
+ * IBS NMI handler: Process the memory access info reported by IBS.
+ *
+ * Reads the MSRs to collect all the information about the reported
+ * memory access, validates the access, stores the valid sample and
+ * schedules the work on this CPU to further process the sample.
+ */
+static int mprof_overflow_handler(unsigned int cmd, struct pt_regs *regs)
+{
+	u64 mem_ctl, mem_data3, mem_data2, paddr, data_src;
+	unsigned long pfn;
+	struct page *page;
+
+	rdmsrq(MSR_AMD64_IBS_MPROF_CTL, mem_ctl);
+	if (!(mem_ctl & IBS_MPROF_CTL_VAL))
+		return NMI_DONE;
+
+	mprof_disable_profiling(mem_ctl);
+	count_vm_event(HWHINT_TOTAL_EVENTS);
+
+	rdmsrq(MSR_AMD64_IBS_MPROF_DATA3, mem_data3);
+	rdmsrq(MSR_AMD64_IBS_MPROF_DATA2, mem_data2);
+
+	data_src = mem_data2 & IBS_MPROF_DATA2_DATASRC_MASK;
+	data_src |= ((mem_data2 & IBS_MPROF_DATA2_DATASRC_MASK_HIGH) >>
+			IBS_MPROF_DATA2_DATASRC_MASK_HIGH_SHIFT);
+
+	switch (data_src) {
+	case IBS_MPROF_DATA2_DATASRC_DRAM:
+		count_vm_event(HWHINT_DRAM_ACCESSES);
+		break;
+	case IBS_MPROF_DATA2_DATASRC_EXT_MEM:
+		count_vm_event(HWHINT_EXTMEM_ACCESSES);
+		break;
+	}
+
+	/* Is linear addr valid? */
+	if (!(mem_data3 & IBS_MPROF_DATA3_LADDR_VALID))
+		goto handled;
+
+	/* Is phys addr valid? */
+	if (!(mem_data3 & IBS_MPROF_DATA3_PADDR_VALID))
+		goto handled;
+	rdmsrq(MSR_AMD64_IBS_MPROF_PHYADDR, paddr);
+
+	pfn = PHYS_PFN(paddr);
+	page = pfn_to_online_page(pfn);
+	if (!page)
+		goto handled;
+
+	/*
+	 * Use the accessing CPU's node as the migration target. On
+	 * topologies where all CPUs reside on toptier nodes (the common
+	 * case), this is the desired behaviour. Topologies that place
+	 * CPUs on lower-tier nodes are rejected later by
+	 * pghot_record_access() via the src_nid == nid early return.
+	 */
+	if (!mprof_push_sample(pfn, numa_node_id(), jiffies))
+		goto handled;
+
+	if (!this_cpu_read(mprof_work_pending)) {
+		this_cpu_write(mprof_work_pending, true);
+		irq_work_queue(this_cpu_ptr(&mprof_irq_work));
+	}
+	count_vm_event(HWHINT_USEFUL_EVENTS);
+
+handled:
+	mprof_enable_profiling();
+	return NMI_HANDLED;
+}
+
+static int get_mprof_lvt_offset(void)
+{
+	u64 val;
+
+	rdmsrq(MSR_AMD64_IBSCTL, val);
+	if (!(val & IBSCTL_MPROF_LVT_OFFSET_VALID))
+		return -EINVAL;
+
+	return (val & IBSCTL_MPROF_LVT_OFFSET_MASK) >>
+		IBSCTL_MPROF_LVT_OFFSET_SHIFT;
+}
+
+static int x86_amd_ibs_mprof_startup(unsigned int cpu)
+{
+	int offset = get_mprof_lvt_offset();
+
+	if (offset < 0) {
+		pr_warn("offset not valid on cpu #%d\n", cpu);
+		return 0;
+	}
+
+	if (setup_APIC_eilvt(offset, 0, APIC_DELIVERY_MODE_NMI, 0)) {
+		pr_warn("APIC setup failed on cpu #%d\n", cpu);
+		return 0;
+	}
+
+	mprof_enable_profiling();
+	return 0;
+}
+
+static int x86_amd_ibs_mprof_teardown(unsigned int cpu)
+{
+	int offset = get_mprof_lvt_offset();
+	u64 mem_ctl;
+
+	if (offset >= 0)
+		setup_APIC_eilvt(offset, 0, APIC_DELIVERY_MODE_FIXED, 1);
+
+	rdmsrq(MSR_AMD64_IBS_MPROF_CTL, mem_ctl);
+	mprof_disable_profiling(mem_ctl);
+
+	return 0;
+}
+
+static int __init mprof_access_profiling_init(void)
+{
+	u32 mprof_caps = cpuid_eax(IBS_CPUID_FEATURES);
+	int cpu, ret;
+
+	if (!(mprof_caps & IBS_CAPS_MEM_PROFILER)) {
+		pr_info("capability is unavailable for access profiling\n");
+		return 0;
+	}
+
+	mprof_s = alloc_percpu_gfp(struct mprof_sample_pcpu, GFP_KERNEL | __GFP_ZERO);
+	if (!mprof_s) {
+		pr_err("alloc_percpu_gfp failed\n");
+		return 0;
+	}
+
+	for_each_possible_cpu(cpu) {
+		INIT_WORK(per_cpu_ptr(&mprof_work, cpu), mprof_work_handler);
+		init_irq_work(per_cpu_ptr(&mprof_irq_work, cpu), mprof_irq_handler);
+	}
+
+	register_nmi_handler(NMI_LOCAL, mprof_overflow_handler, 0, "ibs-memprof");
+
+	ret = cpuhp_setup_state(CPUHP_AP_MM_AMD_IBS_MEMPROF_STARTING,
+				"x86/amd/ibs_mprof:starting",
+				x86_amd_ibs_mprof_startup,
+				x86_amd_ibs_mprof_teardown);
+
+	if (ret) {
+		unregister_nmi_handler(NMI_LOCAL, "ibs-memprof");
+		free_percpu(mprof_s);
+		pr_err("cpuhp_setup_state failed: %d\n", ret);
+	} else {
+		pr_info("IBS Memory Profiler setup for memory access profiling\n");
+	}
+	return 0;
+}
+
+device_initcall(mprof_access_profiling_init);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 22ba327ec227..feaa3f571726 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -150,6 +150,7 @@ enum cpuhp_state {
 	CPUHP_AP_PERF_X86_AMD_UNCORE_STARTING,
 	CPUHP_AP_PERF_X86_STARTING,
 	CPUHP_AP_PERF_X86_AMD_IBS_STARTING,
+	CPUHP_AP_MM_AMD_IBS_MEMPROF_STARTING,
 	CPUHP_AP_PERF_XTENSA_STARTING,
 	CPUHP_AP_ARM_VFP_STARTING,
 	CPUHP_AP_ARM64_DEBUG_MONITORS_STARTING,
diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 58d510711bd4..a9c04a9735c6 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -179,6 +179,12 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 		PGHOT_RECORDED_ACCESSES,
 		PGHOT_RECORDED_HINTFAULTS,
 		PGHOT_RECORDED_HWHINTS,
+#ifdef CONFIG_HWMEM_PROFILER
+		HWHINT_TOTAL_EVENTS,
+		HWHINT_DRAM_ACCESSES,
+		HWHINT_EXTMEM_ACCESSES,
+		HWHINT_USEFUL_EVENTS,
+#endif /* CONFIG_HWMEM_PROFILER */
 #endif /* CONFIG_PGHOT */
 		NR_VM_EVENT_ITEMS
 };
diff --git a/mm/Kconfig b/mm/Kconfig
index cc4b5685ecd4..674cfcea7bb0 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -1494,6 +1494,15 @@ config PGHOT_PRECISE
 	  4 bytes per page against the default one byte per page. Preferable
 	  to enable this on systems with multiple nodes in toptier.
 
+config HWMEM_PROFILER
+	bool
+	depends on PGHOT
+	help
+	  Umbrella symbol enabled by any in-kernel driver that forwards
+	  hardware-observed memory accesses to the pghot subsystem (for
+	  example AMD_IBS_MEMPROF on x86_64). Drivers select this; users
+	  do not enable it directly.
+
 source "mm/damon/Kconfig"
 
 endmenu
diff --git a/mm/vmstat.c b/mm/vmstat.c
index da668ff05032..06e7ae06519e 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1493,6 +1493,12 @@ const char * const vmstat_text[] = {
 	[I(PGHOT_RECORDED_ACCESSES)]		= "pghot_recorded_accesses",
 	[I(PGHOT_RECORDED_HINTFAULTS)]		= "pghot_recorded_hintfaults",
 	[I(PGHOT_RECORDED_HWHINTS)]		= "pghot_recorded_hwhints",
+#ifdef CONFIG_HWMEM_PROFILER
+	[I(HWHINT_TOTAL_EVENTS)]		= "hwhint_total_events",
+	[I(HWHINT_DRAM_ACCESSES)]		= "hwhint_dram_accesses",
+	[I(HWHINT_EXTMEM_ACCESSES)]		= "hwhint_extmem_accesses",
+	[I(HWHINT_USEFUL_EVENTS)]		= "hwhint_useful_events",
+#endif /* CONFIG_HWMEM_PROFILER */
 #endif /* CONFIG_PGHOT */
 #undef I
 #endif /* CONFIG_VM_EVENT_COUNTERS */
-- 
2.34.1