[tip: x86/mm] x86/mm: Simplify PAE PGD sharing macros

[tip-bot2 for Dave Hansen]

The following commit has been merged into the x86/mm branch of tip:

Commit-ID:     45fb940563f80b8138f465f18d71c2d3e4a0724e
Gitweb:        https://git.kernel.org/tip/45fb940563f80b8138f465f18d71c2d3e4a0724e
Author:        Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
AuthorDate:    Mon, 14 Apr 2025 10:32:38 -07:00
Committer:     Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
CommitterDate: Thu, 17 Apr 2025 10:39:25 -07:00

x86/mm: Simplify PAE PGD sharing macros

There are a few too many levels of abstraction here.

First, just expand the PREALLOCATED_PMDS macro in place to make it
clear that it is only conditional on PTI.

Second, MAX_PREALLOCATED_PMDS is only used in one spot for an
on-stack allocation. It has a *maximum* value of 4. Do not bother
with the macro MAX() magic.  Just set it to 4.

Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/all/20250414173238.6E3CDA56%40davehans-spike.ostc.intel.com
---
 arch/x86/mm/pgtable.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index f1c5886..027e1d3 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -68,12 +68,6 @@ static inline void pgd_list_del(pgd_t *pgd)
 	list_del(&ptdesc->pt_list);
 }
 
-#define UNSHARED_PTRS_PER_PGD				\
-	(SHARED_KERNEL_PMD ? KERNEL_PGD_BOUNDARY : PTRS_PER_PGD)
-#define MAX_UNSHARED_PTRS_PER_PGD			\
-	MAX_T(size_t, KERNEL_PGD_BOUNDARY, PTRS_PER_PGD)
-
-
 static void pgd_set_mm(pgd_t *pgd, struct mm_struct *mm)
 {
 	virt_to_ptdesc(pgd)->pt_mm = mm;
@@ -132,8 +126,9 @@ static void pgd_dtor(pgd_t *pgd)
  * not shared between pagetables (!SHARED_KERNEL_PMDS), we allocate
  * and initialize the kernel pmds here.
  */
-#define PREALLOCATED_PMDS	UNSHARED_PTRS_PER_PGD
-#define MAX_PREALLOCATED_PMDS	MAX_UNSHARED_PTRS_PER_PGD
+#define PREALLOCATED_PMDS	(static_cpu_has(X86_FEATURE_PTI) ? \
+					PTRS_PER_PGD : KERNEL_PGD_BOUNDARY)
+#define MAX_PREALLOCATED_PMDS	PTRS_PER_PGD
 
 /*
  * We allocate separate PMDs for the kernel part of the user page-table