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Message-ID: <20260131132848.254084-18-vdonnefort@google.com>
Date: Sat, 31 Jan 2026 13:28:35 +0000
From: Vincent Donnefort <vdonnefort@...gle.com>
To: rostedt@...dmis.org, mhiramat@...nel.org, mathieu.desnoyers@...icios.com,
linux-trace-kernel@...r.kernel.org, maz@...nel.org, oliver.upton@...ux.dev,
joey.gouly@....com, suzuki.poulose@....com, yuzenghui@...wei.com
Cc: kvmarm@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
jstultz@...gle.com, qperret@...gle.com, will@...nel.org,
aneesh.kumar@...nel.org, kernel-team@...roid.com,
linux-kernel@...r.kernel.org, Vincent Donnefort <vdonnefort@...gle.com>
Subject: [PATCH v11 17/30] tracing: load/unload page callbacks for simple_ring_buffer
Add load/unload callback used for each admitted page in the ring-buffer.
This will be later useful for the pKVM hypervisor which uses a different
VA space and need to dynamically map/unmap the ring-buffer pages.
Signed-off-by: Vincent Donnefort <vdonnefort@...gle.com>
diff --git a/include/linux/simple_ring_buffer.h b/include/linux/simple_ring_buffer.h
index 2c4c0ae336bc..21aec556293e 100644
--- a/include/linux/simple_ring_buffer.h
+++ b/include/linux/simple_ring_buffer.h
@@ -54,4 +54,12 @@ int simple_ring_buffer_reset(struct simple_rb_per_cpu *cpu_buffer);
int simple_ring_buffer_swap_reader_page(struct simple_rb_per_cpu *cpu_buffer);
+int simple_ring_buffer_init_mm(struct simple_rb_per_cpu *cpu_buffer,
+ struct simple_buffer_page *bpages,
+ const struct ring_buffer_desc *desc,
+ void *(*load_page)(unsigned long va),
+ void (*unload_page)(void *va));
+
+void simple_ring_buffer_unload_mm(struct simple_rb_per_cpu *cpu_buffer,
+ void (*unload_page)(void *));
#endif
diff --git a/kernel/trace/simple_ring_buffer.c b/kernel/trace/simple_ring_buffer.c
index 88afd28ffef7..2adfeb5a8f4d 100644
--- a/kernel/trace/simple_ring_buffer.c
+++ b/kernel/trace/simple_ring_buffer.c
@@ -71,7 +71,7 @@ static void simple_bpage_reset(struct simple_buffer_page *bpage)
local_set(&bpage->page->commit, 0);
}
-static void simple_bpage_init(struct simple_buffer_page *bpage, unsigned long page)
+static void simple_bpage_init(struct simple_buffer_page *bpage, void *page)
{
INIT_LIST_HEAD(&bpage->link);
bpage->page = (struct buffer_data_page *)page;
@@ -376,19 +376,15 @@ int simple_ring_buffer_reset(struct simple_rb_per_cpu *cpu_buffer)
}
EXPORT_SYMBOL_GPL(simple_ring_buffer_reset);
-/**
- * simple_ring_buffer_init - Init @cpu_buffer based on @desc
- *
- * @cpu_buffer: A simple_rb_per_cpu buffer to init, allocated by the caller.
- * @bpages: Array of simple_buffer_pages, with as many elements as @desc->nr_page_va
- * @desc: A ring_buffer_desc
- *
- * Returns: 0 on success or -EINVAL if the content of @desc is invalid
- */
-int simple_ring_buffer_init(struct simple_rb_per_cpu *cpu_buffer, struct simple_buffer_page *bpages,
- const struct ring_buffer_desc *desc)
+int simple_ring_buffer_init_mm(struct simple_rb_per_cpu *cpu_buffer,
+ struct simple_buffer_page *bpages,
+ const struct ring_buffer_desc *desc,
+ void *(*load_page)(unsigned long va),
+ void (*unload_page)(void *va))
{
struct simple_buffer_page *bpage = bpages;
+ int ret = 0;
+ void *page;
int i;
/* At least 1 reader page and two pages in the ring-buffer */
@@ -397,15 +393,22 @@ int simple_ring_buffer_init(struct simple_rb_per_cpu *cpu_buffer, struct simple_
memset(cpu_buffer, 0, sizeof(*cpu_buffer));
- cpu_buffer->bpages = bpages;
+ cpu_buffer->meta = load_page(desc->meta_va);
+ if (!cpu_buffer->meta)
+ return -EINVAL;
- cpu_buffer->meta = (void *)desc->meta_va;
memset(cpu_buffer->meta, 0, sizeof(*cpu_buffer->meta));
cpu_buffer->meta->meta_page_size = PAGE_SIZE;
cpu_buffer->meta->nr_subbufs = cpu_buffer->nr_pages;
/* The reader page is not part of the ring initially */
- simple_bpage_init(bpage, desc->page_va[0]);
+ page = load_page(desc->page_va[0]);
+ if (!page) {
+ unload_page(cpu_buffer->meta);
+ return -EINVAL;
+ }
+
+ simple_bpage_init(bpage, page);
bpage->id = 0;
cpu_buffer->nr_pages = 1;
@@ -415,7 +418,13 @@ int simple_ring_buffer_init(struct simple_rb_per_cpu *cpu_buffer, struct simple_
cpu_buffer->head_page = bpage + 1;
for (i = 1; i < desc->nr_page_va; i++) {
- simple_bpage_init(++bpage, desc->page_va[i]);
+ page = load_page(desc->page_va[i]);
+ if (!page) {
+ ret = -EINVAL;
+ break;
+ }
+
+ simple_bpage_init(++bpage, page);
bpage->link.next = &(bpage + 1)->link;
bpage->link.prev = &(bpage - 1)->link;
@@ -424,6 +433,14 @@ int simple_ring_buffer_init(struct simple_rb_per_cpu *cpu_buffer, struct simple_
cpu_buffer->nr_pages = i + 1;
}
+ if (ret) {
+ for (i--; i >= 0; i--)
+ unload_page((void *)desc->page_va[i]);
+ unload_page(cpu_buffer->meta);
+
+ return ret;
+ }
+
/* Close the ring */
bpage->link.next = &cpu_buffer->tail_page->link;
cpu_buffer->tail_page->link.prev = &bpage->link;
@@ -431,25 +448,50 @@ int simple_ring_buffer_init(struct simple_rb_per_cpu *cpu_buffer, struct simple_
/* The last init'ed page points to the head page */
simple_bpage_set_head_link(bpage);
+ cpu_buffer->bpages = bpages;
+
return 0;
}
-EXPORT_SYMBOL_GPL(simple_ring_buffer_init);
+
+static void *__load_page(unsigned long page)
+{
+ return (void *)page;
+}
+
+static void __unload_page(void *page) { }
/**
- * simple_ring_buffer_unload - Prepare @cpu_buffer for deletion
+ * simple_ring_buffer_init - Init @cpu_buffer based on @desc
*
- * @cpu_buffer: A simple_rb_per_cpu that will be deleted.
+ * @cpu_buffer: A simple_rb_per_cpu buffer to init, allocated by the caller.
+ * @bpages: Array of simple_buffer_pages, with as many elements as @desc->nr_page_va
+ * @desc: A ring_buffer_desc
+ *
+ * Returns: 0 on success or -EINVAL if the content of @desc is invalid
*/
-void simple_ring_buffer_unload(struct simple_rb_per_cpu *cpu_buffer)
+int simple_ring_buffer_init(struct simple_rb_per_cpu *cpu_buffer, struct simple_buffer_page *bpages,
+ const struct ring_buffer_desc *desc)
{
+ return simple_ring_buffer_init_mm(cpu_buffer, bpages, desc, __load_page, __unload_page);
+}
+EXPORT_SYMBOL_GPL(simple_ring_buffer_init);
+
+void simple_ring_buffer_unload_mm(struct simple_rb_per_cpu *cpu_buffer,
+ void (*unload_page)(void *))
+{
+ int p;
+
if (!simple_rb_loaded(cpu_buffer))
return;
simple_rb_enable_tracing(cpu_buffer, false);
+ unload_page(cpu_buffer->meta);
+ for (p = 0; p < cpu_buffer->nr_pages; p++)
+ unload_page(cpu_buffer->bpages[p].page);
+
cpu_buffer->bpages = NULL;
}
-EXPORT_SYMBOL_GPL(simple_ring_buffer_unload);
/**
* simple_ring_buffer_enable_tracing - Enable or disable writing to @cpu_buffer
@@ -459,6 +501,12 @@ EXPORT_SYMBOL_GPL(simple_ring_buffer_unload);
*
* Returns 0 on success or -ENODEV if @cpu_buffer was unloaded
*/
+void simple_ring_buffer_unload(struct simple_rb_per_cpu *cpu_buffer)
+{
+ return simple_ring_buffer_unload_mm(cpu_buffer, __unload_page);
+}
+EXPORT_SYMBOL_GPL(simple_ring_buffer_unload);
+
int simple_ring_buffer_enable_tracing(struct simple_rb_per_cpu *cpu_buffer, bool enable)
{
if (!simple_rb_loaded(cpu_buffer))
--
2.53.0.rc1.225.gd81095ad13-goog
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