On 11/17/22 15:23, Marco Elver wrote:
> Yes - it's the 'level != PG_LEVEL_4K'.
That plus the bisect made it pretty easy to find, thanks for the effort!
Could you double-check that the attached patch fixes it? It seemed to
for me.
The issue was that the new "No changes, easy!" check in the suspect
commit didn't check the cpa->force_split option. It didn't split down
to 4k and then all hell broke loose.
Oh, and I totally misread the kfence ability to tolerate partial TLB
flushes. Sorry for the noise there!
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 220361ceb997..9b4e2ad957f6 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1727,7 +1727,8 @@ static int __change_page_attr_set_clr(struct cpa_data *cpa, int primary)
/*
* No changes, easy!
*/
- if (!(pgprot_val(cpa->mask_set) | pgprot_val(cpa->mask_clr)))
+ if (!(pgprot_val(cpa->mask_set) | pgprot_val(cpa->mask_clr))
+ && !cpa->force_split)
return ret;
while (rempages) {
