Re: [PATCH v1 09/11] x86/mm/pat: remove MEMTYPE_*_MATCH

David Hildenbrand
2025-05-05T12:11:03Z

On 28.04.25 22:23, Lorenzo Stoakes wrote:
> On Fri, Apr 25, 2025 at 10:17:13AM +0200, David Hildenbrand wrote:
>> The "memramp() shrinking" scenario no longer applies, so let's remove
>> that now-unnecessary handling.
>
> I wonder if we could remove even more of the code here given the
> simplifications here? But not a big deal.

It might make sense to inline memtype_match().

diff --git a/arch/x86/mm/pat/memtype_interval.c b/arch/x86/mm/pat/memtype_interval.c
index 9d03f0dbc4715..e5844ed1311ed 100644
--- a/arch/x86/mm/pat/memtype_interval.c
+++ b/arch/x86/mm/pat/memtype_interval.c
@@ -49,21 +49,6 @@ INTERVAL_TREE_DEFINE(struct memtype, rb, u64, subtree_max_end,

static struct rb_root_cached memtype_rbroot = RB_ROOT_CACHED;

-static struct memtype *memtype_match(u64 start, u64 end)
-{
- struct memtype *entry_match;
-
- entry_match = interval_iter_first(&memtype_rbroot, start, end-1);
-
- while (entry_match != NULL && entry_match->start < end) {
- if (entry_match->start == start && entry_match->end == end)
- return entry_match;
- entry_match = interval_iter_next(entry_match, start, end-1);
- }
-
- return NULL; /* Returns NULL if there is no match */
-}
-
static int memtype_check_conflict(u64 start, u64 end,
enum page_cache_mode reqtype,
enum page_cache_mode *newtype)
@@ -119,14 +104,16 @@ int memtype_check_insert(struct memtype *entry_new, enum page_cache_mode *ret_ty

struct memtype *memtype_erase(u64 start, u64 end)
{
- struct memtype *entry_old;
-
- entry_old = memtype_match(start, end);
- if (!entry_old)
- return ERR_PTR(-EINVAL);
-
- interval_remove(entry_old, &memtype_rbroot);
- return entry_old;
+ struct memtype *entry = interval_iter_first(&memtype_rbroot, start, end - 1);
+
+ while (entry && entry->start < end) {
+ if (entry->start == start && entry->end == end) {
+ interval_remove(entry, &memtype_rbroot);
+ return entry;
+ }
+ entry = interval_iter_next(entry, start, end - 1);
+ }
+ return ERR_PTR(-EINVAL);
}

struct memtype *memtype_lookup(u64 addr)

Thanks for all the review!

--
Cheers,

David / dhildenb