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tracing: load/unload page callbacks for simple_ring_buffer

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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.

Link: https://patch.msgid.link/20260309162516.2623589-18-vdonnefort@google.com
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Vincent Donnefort 2026-03-09 16:25:03 +00:00 committed by Steven Rostedt (Google)
parent c88d510584
commit 635923081c
2 changed files with 112 additions and 51 deletions
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8
include/linux/simple_ring_buffer.h
View File

@ -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

155
kernel/trace/simple_ring_buffer.c
View File

@ -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;
@ -372,6 +372,90 @@ int simple_ring_buffer_reset(struct simple_rb_per_cpu *cpu_buffer)
}
EXPORT_SYMBOL_GPL(simple_ring_buffer_reset);
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 */
if (desc->nr_page_va < 3)
return -EINVAL;
memset(cpu_buffer, 0, sizeof(*cpu_buffer));
cpu_buffer->meta = load_page(desc->meta_va);
if (!cpu_buffer->meta)
return -EINVAL;
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 */
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;
cpu_buffer->reader_page = bpage;
cpu_buffer->tail_page = bpage + 1;
cpu_buffer->head_page = bpage + 1;
for (i = 1; i < desc->nr_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;
bpage->id = i;
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;
/* The last init'ed page points to the head page */
simple_bpage_set_head_link(bpage);
cpu_buffer->bpages = bpages;
return 0;
}
static void *__load_page(unsigned long page)
{
return (void *)page;
}
static void __unload_page(void *page) { }
/**
* simple_ring_buffer_init - Init @cpu_buffer based on @desc
* @cpu_buffer: A simple_rb_per_cpu buffer to init, allocated by the caller.
@ -383,65 +467,34 @@ EXPORT_SYMBOL_GPL(simple_ring_buffer_reset);
int simple_ring_buffer_init(struct simple_rb_per_cpu *cpu_buffer, struct simple_buffer_page *bpages,
const struct ring_buffer_desc *desc)
{
struct simple_buffer_page *bpage = bpages;
int i;
/* At least 1 reader page and two pages in the ring-buffer */
if (desc->nr_page_va < 3)
return -EINVAL;
memset(cpu_buffer, 0, sizeof(*cpu_buffer));
cpu_buffer->bpages = bpages;
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]);
bpage->id = 0;
cpu_buffer->nr_pages = 1;
cpu_buffer->reader_page = bpage;
cpu_buffer->tail_page = bpage + 1;
cpu_buffer->head_page = bpage + 1;
for (i = 1; i < desc->nr_page_va; i++) {
simple_bpage_init(++bpage, desc->page_va[i]);
bpage->link.next = &(bpage + 1)->link;
bpage->link.prev = &(bpage - 1)->link;
bpage->id = i;
cpu_buffer->nr_pages = i + 1;
}
/* Close the ring */
bpage->link.next = &cpu_buffer->tail_page->link;
cpu_buffer->tail_page->link.prev = &bpage->link;
/* The last init'ed page points to the head page */
simple_bpage_set_head_link(bpage);
return 0;
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;
}
/**
* simple_ring_buffer_unload - Prepare @cpu_buffer for deletion
* @cpu_buffer: A simple_rb_per_cpu that will be deleted.
*/
void simple_ring_buffer_unload(struct simple_rb_per_cpu *cpu_buffer)
{
if (!simple_rb_loaded(cpu_buffer))
return;
simple_rb_enable_tracing(cpu_buffer, false);
cpu_buffer->bpages = NULL;
return simple_ring_buffer_unload_mm(cpu_buffer, __unload_page);
}
EXPORT_SYMBOL_GPL(simple_ring_buffer_unload);