Commit 82f12001 authored by Dave Hansen's avatar Dave Hansen
Browse files

x86/mm: Fix up comments around PMD preallocation 



The "paravirt environment" is no longer in the tree. Axe that part of the
comment. Also add a blurb to remind readers that "USER_PMDS" refer to
the PTI user *copy* of the page tables, not the user *portion*.

Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20250414173240.5B1AB322%40davehans-spike.ostc.intel.com
parent 45fb9405

arch/x86/mm/pgtable.c

+5 −4
Original line number Diff line number Diff line
@@ -121,16 +121,17 @@ static void pgd_dtor(pgd_t *pgd) 
 * processor notices the update.  Since this is expensive, and

 * all 4 top-level entries are used almost immediately in a

 * new process's life, we just pre-populate them here.

 *

 * Also, if we're in a paravirt environment where the kernel pmd is

 * not shared between pagetables (!SHARED_KERNEL_PMDS), we allocate

 * and initialize the kernel pmds here.

 */

#define PREALLOCATED_PMDS	(static_cpu_has(X86_FEATURE_PTI) ? \

					PTRS_PER_PGD : KERNEL_PGD_BOUNDARY)

#define MAX_PREALLOCATED_PMDS	PTRS_PER_PGD



/*

 * "USER_PMDS" are the PMDs for the user copy of the page tables when

 * PTI is enabled. They do not exist when PTI is disabled.  Note that

 * this is distinct from the user _portion_ of the kernel page tables

 * which always exists.

 *

 * We allocate separate PMDs for the kernel part of the user page-table

 * when PTI is enabled. We need them to map the per-process LDT into the

 * user-space page-table.