[RFC PATCH v3 4/4] mm/damon/paddr: support perf event based access check

[Akinobu Mita <akinobu.mita@gmail.com>]

This patch adds perf event based access checks for physical address
spaces monitoring.

The implementation is very similar to that described in perf event based
access check for virtual address space monitoring.

However, for perf events that can be specified with physical address
spaces monitoring, the data source address corresponding to the sample
must be obtainable as a physical address.  In other words,
PERF_SAMPLE_DATA_SRC and PERF_SAMPLE_PHYS_ADDR must be specifiable in
perf_event_attr.sample_type.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
 mm/damon/core.c       |  3 +++
 mm/damon/ops-common.h |  6 ++++++
 mm/damon/paddr.c      | 41 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 50 insertions(+)

diff --git a/mm/damon/core.c b/mm/damon/core.c
index def72672982a..bf9318c13d0b 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -3031,6 +3031,9 @@ static unsigned int kdamond_check_perf_event_reported_accesses(struct damon_ctx
 	if (damon_target_has_pid(ctx)) {
 		list_for_each_entry(event, &ctx->perf_events, list)
 			damon_va_perf_check_accesses(ctx, event);
+	} else {
+		list_for_each_entry(event, &ctx->perf_events, list)
+			damon_pa_perf_check_accesses(ctx, event);
 	}
 
 	damon_for_each_target(t, ctx) {
diff --git a/mm/damon/ops-common.h b/mm/damon/ops-common.h
index da39abe07cfc..f6db6bc4d882 100644
--- a/mm/damon/ops-common.h
+++ b/mm/damon/ops-common.h
@@ -28,6 +28,7 @@ bool damos_ops_has_filter(struct damos *s);
 
 void damon_perf_prepare_access_checks(struct damon_ctx *ctx, struct damon_perf_event *event);
 void damon_va_perf_check_accesses(struct damon_ctx *ctx, struct damon_perf_event *event);
+void damon_pa_perf_check_accesses(struct damon_ctx *ctx, struct damon_perf_event *event);
 int damon_perf_init(struct damon_ctx *ctx, struct damon_perf_event *event);
 void damon_perf_cleanup(struct damon_ctx *ctx, struct damon_perf_event *event);
 
@@ -66,6 +67,11 @@ static inline void damon_va_perf_check_accesses(struct damon_ctx *ctx,
 {
 }
 
+static inline void damon_pa_perf_check_accesses(struct damon_ctx *ctx,
+		struct damon_perf_event *event)
+{
+}
+
 static inline int damon_perf_init(struct damon_ctx *ctx, struct damon_perf_event *event)
 {
 	return 0;
diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index 5cdcc5037cbc..97df21281fb1 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -363,6 +363,47 @@ static int damon_pa_scheme_score(struct damon_ctx *context,
 	return DAMOS_MAX_SCORE;
 }
 
+#ifdef CONFIG_PERF_EVENTS
+
+void damon_pa_perf_check_accesses(struct damon_ctx *ctx, struct damon_perf_event *event)
+{
+	struct damon_perf *perf = event->priv;
+	struct damon_target *t;
+	unsigned int tidx = 0;
+
+	if (!perf)
+		return;
+
+	damon_paddr_histogram_init(&perf->paddr_histogram);
+
+	damon_perf_populate_paddr_histogram(ctx, event);
+
+	damon_for_each_target(t, ctx) {
+		struct damon_region *r;
+
+		damon_for_each_region(r, t) {
+			unsigned long addr;
+
+			if (r->access_reported)
+				continue;
+
+			for (addr = r->ar.start; addr < r->ar.end; addr += PAGE_SIZE) {
+				if (damon_paddr_histogram_count(&perf->paddr_histogram,
+									addr & PAGE_MASK)) {
+					damon_update_region_access_rate(r, true, &ctx->attrs);
+					r->access_reported = true;
+					break;
+				}
+			}
+		}
+		tidx++;
+	}
+
+	damon_paddr_histogram_destroy(&perf->paddr_histogram);
+}
+
+#endif /* CONFIG_PERF_EVENTS */
+
 static int __init damon_pa_initcall(void)
 {
 	struct damon_operations ops = {
-- 
2.43.0