perf/x86/intel: Allocate arch-PEBS buffer and initialize PEBS_BASE MSR

Arch-PEBS introduces a new MSR IA32_PEBS_BASE to store the arch-PEBS
buffer physical address. This patch allocates arch-PEBS buffer and then
initialize IA32_PEBS_BASE MSR with the buffer physical address.

Co-developed-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20251029102136.61364-10-dapeng1.mi@linux.intel.com

Author: Dapeng Mi

arch/x86/events/intel/core.c

@@ -5227,7 +5227,13 @@ int intel_cpuc_prepare(struct cpu_hw_events *cpuc, int cpu)
 
 static int intel_pmu_cpu_prepare(int cpu)
 {
-	return intel_cpuc_prepare(&per_cpu(cpu_hw_events, cpu), cpu);
+	int ret;
+
+	ret = intel_cpuc_prepare(&per_cpu(cpu_hw_events, cpu), cpu);
+	if (ret)
+		return ret;
+
+	return alloc_arch_pebs_buf_on_cpu(cpu);
 }
 
 static void flip_smm_bit(void *data)
@@ -5458,6 +5464,7 @@ static void intel_pmu_cpu_starting(int cpu)
 		return;
 
 	init_debug_store_on_cpu(cpu);
+	init_arch_pebs_on_cpu(cpu);
 	/*
 	 * Deal with CPUs that don't clear their LBRs on power-up, and that may
 	 * even boot with LBRs enabled.
@@ -5555,6 +5562,7 @@ static void free_excl_cntrs(struct cpu_hw_events *cpuc)
 static void intel_pmu_cpu_dying(int cpu)
 {
 	fini_debug_store_on_cpu(cpu);
+	fini_arch_pebs_on_cpu(cpu);
 }
 
 void intel_cpuc_finish(struct cpu_hw_events *cpuc)
@@ -5575,6 +5583,7 @@ static void intel_pmu_cpu_dead(int cpu)
 {
 	struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);
 
+	release_arch_pebs_buf_on_cpu(cpu);
 	intel_cpuc_finish(cpuc);
 
 	if (is_hybrid() && cpuc->pmu)

arch/x86/events/intel/ds.c

@@ -625,13 +625,18 @@ static int alloc_pebs_buffer(int cpu)
 	int max, node = cpu_to_node(cpu);
 	void *buffer, *insn_buff, *cea;
 
-	if (!x86_pmu.ds_pebs)
+	if (!intel_pmu_has_pebs())
 		return 0;
 
 	buffer = dsalloc_pages(bsiz, GFP_KERNEL, cpu);
 	if (unlikely(!buffer))
 		return -ENOMEM;
 
+	if (x86_pmu.arch_pebs) {
+		hwev->pebs_vaddr = buffer;
+		return 0;
+	}
+
 	/*
 	 * HSW+ already provides us the eventing ip; no need to allocate this
 	 * buffer then.
@@ -644,7 +649,7 @@ static int alloc_pebs_buffer(int cpu)
 		}
 		per_cpu(insn_buffer, cpu) = insn_buff;
 	}
-	hwev->ds_pebs_vaddr = buffer;
+	hwev->pebs_vaddr = buffer;
 	/* Update the cpu entry area mapping */
 	cea = &get_cpu_entry_area(cpu)->cpu_debug_buffers.pebs_buffer;
 	ds->pebs_buffer_base = (unsigned long) cea;
@@ -660,17 +665,20 @@ static void release_pebs_buffer(int cpu)
 	struct cpu_hw_events *hwev = per_cpu_ptr(&cpu_hw_events, cpu);
 	void *cea;
 
-	if (!x86_pmu.ds_pebs)
+	if (!intel_pmu_has_pebs())
 		return;
 
-	kfree(per_cpu(insn_buffer, cpu));
-	per_cpu(insn_buffer, cpu) = NULL;
+	if (x86_pmu.ds_pebs) {
+		kfree(per_cpu(insn_buffer, cpu));
+		per_cpu(insn_buffer, cpu) = NULL;
 
-	/* Clear the fixmap */
-	cea = &get_cpu_entry_area(cpu)->cpu_debug_buffers.pebs_buffer;
-	ds_clear_cea(cea, x86_pmu.pebs_buffer_size);
-	dsfree_pages(hwev->ds_pebs_vaddr, x86_pmu.pebs_buffer_size);
-	hwev->ds_pebs_vaddr = NULL;
+		/* Clear the fixmap */
+		cea = &get_cpu_entry_area(cpu)->cpu_debug_buffers.pebs_buffer;
+		ds_clear_cea(cea, x86_pmu.pebs_buffer_size);
+	}
+
+	dsfree_pages(hwev->pebs_vaddr, x86_pmu.pebs_buffer_size);
+	hwev->pebs_vaddr = NULL;
 }
 
 static int alloc_bts_buffer(int cpu)
@@ -823,6 +831,56 @@ void reserve_ds_buffers(void)
 	}
 }
 
+inline int alloc_arch_pebs_buf_on_cpu(int cpu)
+{
+	if (!x86_pmu.arch_pebs)
+		return 0;
+
+	return alloc_pebs_buffer(cpu);
+}
+
+inline void release_arch_pebs_buf_on_cpu(int cpu)
+{
+	if (!x86_pmu.arch_pebs)
+		return;
+
+	release_pebs_buffer(cpu);
+}
+
+void init_arch_pebs_on_cpu(int cpu)
+{
+	struct cpu_hw_events *cpuc = per_cpu_ptr(&cpu_hw_events, cpu);
+	u64 arch_pebs_base;
+
+	if (!x86_pmu.arch_pebs)
+		return;
+
+	if (!cpuc->pebs_vaddr) {
+		WARN(1, "Fail to allocate PEBS buffer on CPU %d\n", cpu);
+		x86_pmu.pebs_active = 0;
+		return;
+	}
+
+	/*
+	 * 4KB-aligned pointer of the output buffer
+	 * (__alloc_pages_node() return page aligned address)
+	 * Buffer Size = 4KB * 2^SIZE
+	 * contiguous physical buffer (__alloc_pages_node() with order)
+	 */
+	arch_pebs_base = virt_to_phys(cpuc->pebs_vaddr) | PEBS_BUFFER_SHIFT;
+	wrmsr_on_cpu(cpu, MSR_IA32_PEBS_BASE, (u32)arch_pebs_base,
+		     (u32)(arch_pebs_base >> 32));
+	x86_pmu.pebs_active = 1;
+}
+
+inline void fini_arch_pebs_on_cpu(int cpu)
+{
+	if (!x86_pmu.arch_pebs)
+		return;
+
+	wrmsr_on_cpu(cpu, MSR_IA32_PEBS_BASE, 0, 0);
+}
+
 /*
  * BTS
  */
@@ -2883,8 +2941,8 @@ static void intel_pmu_drain_arch_pebs(struct pt_regs *iregs,
 		return;
 	}
 
-	base = cpuc->ds_pebs_vaddr;
-	top = (void *)((u64)cpuc->ds_pebs_vaddr +
+	base = cpuc->pebs_vaddr;
+	top = (void *)((u64)cpuc->pebs_vaddr +
 		       (index.wr << ARCH_PEBS_INDEX_WR_SHIFT));
 
 	index.wr = 0;

arch/x86/events/perf_event.h

@@ -283,8 +283,9 @@ struct cpu_hw_events {
 	 * Intel DebugStore bits
 	 */
 	struct debug_store	*ds;
-	void			*ds_pebs_vaddr;
 	void			*ds_bts_vaddr;
+	/* DS based PEBS or arch-PEBS buffer address */
+	void			*pebs_vaddr;
 	u64			pebs_enabled;
 	int			n_pebs;
 	int			n_large_pebs;
@@ -1617,6 +1618,14 @@ extern void intel_cpuc_finish(struct cpu_hw_events *cpuc);
 
 int intel_pmu_init(void);
 
+int alloc_arch_pebs_buf_on_cpu(int cpu);
+
+void release_arch_pebs_buf_on_cpu(int cpu);
+
+void init_arch_pebs_on_cpu(int cpu);
+
+void fini_arch_pebs_on_cpu(int cpu);
+
 void init_debug_store_on_cpu(int cpu);
 
 void fini_debug_store_on_cpu(int cpu);

arch/x86/include/asm/intel_ds.h

@@ -4,7 +4,8 @@
 #include <linux/percpu-defs.h>
 
 #define BTS_BUFFER_SIZE		(PAGE_SIZE << 4)
-#define PEBS_BUFFER_SIZE	(PAGE_SIZE << 4)
+#define PEBS_BUFFER_SHIFT	4
+#define PEBS_BUFFER_SIZE	(PAGE_SIZE << PEBS_BUFFER_SHIFT)
 
 /* The maximal number of PEBS events: */
 #define MAX_PEBS_EVENTS_FMT4	8