diff options
| author | Dave Hansen <dave.hansen@linux.intel.com> | 2022-11-18 07:16:16 -0800 |
|---|---|---|
| committer | Dave Hansen <dave.hansen@linux.intel.com> | 2022-12-15 10:37:28 -0800 |
| commit | 3e844d842d49cdbe61a4b338bdd512654179488a (patch) | |
| tree | fea8b53ff4d583986b98be3bbf60f1ee65cee0b7 /arch | |
| parent | 1cfaac2400c73378e78182a706be0f3ac8b93cd7 (diff) | |
| download | linux-3e844d842d49cdbe61a4b338bdd512654179488a.tar.bz2 | |
x86/mm: Ensure forced page table splitting
There are a few kernel users like kfence that require 4k pages to work
correctly and do not support large mappings. They use set_memory_4k()
to break down those large mappings.
That, in turn relies on cpa_data->force_split option to indicate to
set_memory code that it should split page tables regardless of whether
the need to be.
But, a recent change added an optimization which would return early
if a set_memory request came in that did not change permissions. It
did not consult ->force_split and would mistakenly optimize away the
splitting that set_memory_4k() needs. This broke kfence.
Skip the same-permission optimization when ->force_split is set.
Fixes: 127960a05548 ("x86/mm: Inhibit _PAGE_NX changes from cpa_process_alias()")
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Tested-by: Marco Elver <elver@google.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/CA+G9fYuFxZTxkeS35VTZMXwQvohu73W3xbZ5NtjebsVvH6hCuA@mail.gmail.com/
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/mm/pat/set_memory.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c index 220361ceb997..0db69514fe29 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) { |