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commit 038ba305fda74c42707cf1ccb6d1d171d8433477
Author: Andrew Cooper <andrew.cooper3@citrix.com>
AuthorDate: Fri Mar 15 17:18:42 2024 +0000
Commit: Andrew Cooper <andrew.cooper3@citrix.com>
CommitDate: Thu Apr 11 13:23:08 2024 +0100

xen/virtual-region: Link the list build time

Given 3 statically initialised objects, its easy to link the list at build
time. There's no need to do it during runtime at boot (and with IRQs-off,
even).

As a consequence, register_virtual_region() can now move inside ifdef
CONFIG_LIVEPATCH like unregister_virtual_region().

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Michal Orzel <michal.orzel@amd.com>
---
xen/common/virtual_region.c | 38 +++++++++++++++++++++++---------------
1 file changed, 23 insertions(+), 15 deletions(-)

diff --git a/xen/common/virtual_region.c b/xen/common/virtual_region.c
index 7d8bdeb612..fe4f53d86b 100644
--- a/xen/common/virtual_region.c
+++ b/xen/common/virtual_region.c
@@ -15,8 +15,19 @@ extern const struct bug_frame
__start_bug_frames_2[], __stop_bug_frames_2[],
__start_bug_frames_3[], __stop_bug_frames_3[];

+/*
+ * For the built-in regions, the double linked list can be constructed at
+ * build time. Forward-declare the elements and their initialisers.
+ */
+static struct list_head virtual_region_list;
+static struct virtual_region core, core_init;
+
+#define LIST_ENTRY_HEAD() { .next = &core.list, .prev = &core_init.list }
+#define LIST_ENTRY_CORE() { .next = &core_init.list, .prev = &virtual_region_list }
+#define LIST_ENTRY_INIT() { .next = &virtual_region_list, .prev = &core.list }
+
static struct virtual_region core = {
- .list = LIST_HEAD_INIT(core.list),
+ .list = LIST_ENTRY_CORE(),
.text_start = _stext,
.text_end = _etext,
.rodata_start = _srodata,
@@ -32,7 +43,7 @@ static struct virtual_region core = {

/* Becomes irrelevant when __init sections are cleared. */
static struct virtual_region core_init __initdata = {
- .list = LIST_HEAD_INIT(core_init.list),
+ .list = LIST_ENTRY_INIT(),
.text_start = _sinittext,
.text_end = _einittext,

@@ -50,7 +61,7 @@ static struct virtual_region core_init __initdata = {
*
* All readers of virtual_region_list MUST use list_for_each_entry_rcu.
*/
-static LIST_HEAD(virtual_region_list);
+static struct list_head virtual_region_list = LIST_ENTRY_HEAD();
static DEFINE_SPINLOCK(virtual_region_lock);
static DEFINE_RCU_READ_LOCK(rcu_virtual_region_lock);

@@ -73,15 +84,6 @@ const struct virtual_region *find_text_region(unsigned long addr)
return region;
}

-void register_virtual_region(struct virtual_region *r)
-{
- unsigned long flags;
-
- spin_lock_irqsave(&virtual_region_lock, flags);
- list_add_tail_rcu(&r->list, &virtual_region_list);
- spin_unlock_irqrestore(&virtual_region_lock, flags);
-}
-
/*
* Suggest inline so when !CONFIG_LIVEPATCH the function is not left
* unreachable after init code is removed.
@@ -96,6 +98,15 @@ static void inline remove_virtual_region(struct virtual_region *r)
}

#ifdef CONFIG_LIVEPATCH
+void register_virtual_region(struct virtual_region *r)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&virtual_region_lock, flags);
+ list_add_tail_rcu(&r->list, &virtual_region_list);
+ spin_unlock_irqrestore(&virtual_region_lock, flags);
+}
+
void unregister_virtual_region(struct virtual_region *r)
{
remove_virtual_region(r);
@@ -155,9 +166,6 @@ void __init setup_virtual_regions(const struct exception_table_entry *start,
{
core_init.ex = core.ex = start;
core_init.ex_end = core.ex_end = end;
-
- register_virtual_region(&core_init);
- register_virtual_region(&core);
}

/*
--
generated by git-patchbot for /home/xen/git/xen.git#staging