On Thu, Nov 17, 2022 at 03:54PM -0800, Dave Hansen wrote:
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.
Yes, that works - thanks!
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)while (rempages) {
Tested-by: Marco Elver elver@google.com