[patch 85/86] um: add support for folded p4d page tables

Andrew Morton
2019-12-05T00:54:32Z

From: Mike Rapoport <rppt@linux.ibm.com>
Subject: um: add support for folded p4d page tables

The UML port uses 4 and 5 level fixups to support higher level page table
directories in the generic VM code.

Implement primitives necessary for the 4th level folding, add walks of p4d
level where appropriate and drop usage of __ARCH_USE_5LEVEL_HACK.

Link: http://lkml.kernel.org/r/1572938135-31886-13-git-send-email-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: Anatoly Pugachev <matorola@gmail.com>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Greg Ungerer <gerg@linux-m68k.org>
Cc: Helge Deller <deller@gmx.de>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Mark Salter <msalter@redhat.com>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Peter Rosin <peda@axentia.se>
Cc: Richard Weinberger <richard@nod.at>
Cc: Rolf Eike Beer <eike-kernel@sf-tec.de>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Russell King <rmk+kernel@armlinux.org.uk>
Cc: Sam Creasey <sammy@sammy.net>
Cc: Vincent Chen <deanbo422@gmail.com>
Cc: Vineet Gupta <Vineet.Gupta1@synopsys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

arch/um/include/asm/pgtable-2level.h | 1
arch/um/include/asm/pgtable-3level.h | 1
arch/um/include/asm/pgtable.h | 3 +
arch/um/kernel/mem.c | 8 ++-
arch/um/kernel/skas/mmu.c | 12 ++++-
arch/um/kernel/skas/uaccess.c | 7 ++-
arch/um/kernel/tlb.c | 56 ++++++++++++++++++++++---
arch/um/kernel/trap.c | 4 +
8 files changed, 78 insertions(+), 14 deletions(-)

--- a/arch/um/include/asm/pgtable-2level.h~um-add-support-for-folded-p4d-page-tables
+++ a/arch/um/include/asm/pgtable-2level.h
@@ -8,7 +8,6 @@
#ifndef __UM_PGTABLE_2LEVEL_H
#define __UM_PGTABLE_2LEVEL_H

-#define __ARCH_USE_5LEVEL_HACK
#include <asm-generic/pgtable-nopmd.h>

/* PGDIR_SHIFT determines what a third-level page table entry can map */
--- a/arch/um/include/asm/pgtable-3level.h~um-add-support-for-folded-p4d-page-tables
+++ a/arch/um/include/asm/pgtable-3level.h
@@ -7,7 +7,6 @@
#ifndef __UM_PGTABLE_3LEVEL_H
#define __UM_PGTABLE_3LEVEL_H

-#define __ARCH_USE_5LEVEL_HACK
#include <asm-generic/pgtable-nopud.h>

/* PGDIR_SHIFT determines what a third-level page table entry can map */
--- a/arch/um/include/asm/pgtable.h~um-add-support-for-folded-p4d-page-tables
+++ a/arch/um/include/asm/pgtable.h
@@ -106,6 +106,9 @@ extern unsigned long end_iomem;
#define pud_newpage(x) (pud_val(x) & _PAGE_NEWPAGE)
#define pud_mkuptodate(x) (pud_val(x) &= ~_PAGE_NEWPAGE)

+#define p4d_newpage(x) (p4d_val(x) & _PAGE_NEWPAGE)
+#define p4d_mkuptodate(x) (p4d_val(x) &= ~_PAGE_NEWPAGE)
+
#define pmd_page(pmd) phys_to_page(pmd_val(pmd) & PAGE_MASK)

#define pte_page(x) pfn_to_page(pte_pfn(x))
--- a/arch/um/kernel/mem.c~um-add-support-for-folded-p4d-page-tables
+++ a/arch/um/kernel/mem.c
@@ -96,6 +96,7 @@ static void __init fixrange_init(unsigne
pgd_t *pgd_base)
{
pgd_t *pgd;
+ p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
int i, j;
@@ -107,7 +108,8 @@ static void __init fixrange_init(unsigne
pgd = pgd_base + i;

for ( ; (i < PTRS_PER_PGD) && (vaddr < end); pgd++, i++) {
- pud = pud_offset(pgd, vaddr);
+ p4d = p4d_offset(pgd, vaddr);
+ pud = pud_offset(p4d, vaddr);
if (pud_none(*pud))
one_md_table_init(pud);
pmd = pmd_offset(pud, vaddr);
@@ -124,6 +126,7 @@ static void __init fixaddr_user_init( vo
#ifdef CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA
long size = FIXADDR_USER_END - FIXADDR_USER_START;
pgd_t *pgd;
+ p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
@@ -144,7 +147,8 @@ static void __init fixaddr_user_init( vo
for ( ; size > 0; size -= PAGE_SIZE, vaddr += PAGE_SIZE,
p += PAGE_SIZE) {
pgd = swapper_pg_dir + pgd_index(vaddr);
- pud = pud_offset(pgd, vaddr);
+ p4d = p4d_offset(pgd, vaddr);
+ pud = pud_offset(p4d, vaddr);
pmd = pmd_offset(pud, vaddr);
pte = pte_offset_kernel(pmd, vaddr);
pte_set_val(*pte, p, PAGE_READONLY);
--- a/arch/um/kernel/skas/mmu.c~um-add-support-for-folded-p4d-page-tables
+++ a/arch/um/kernel/skas/mmu.c
@@ -19,15 +19,21 @@ static int init_stub_pte(struct mm_struc
unsigned long kernel)
{
pgd_t *pgd;
+ p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;

pgd = pgd_offset(mm, proc);
- pud = pud_alloc(mm, pgd, proc);
- if (!pud)
+
+ p4d = p4d_alloc(mm, pgd, proc);
+ if (!p4d)
goto out;

+ pud = pud_alloc(mm, p4d, proc);
+ if (!pud)
+ goto out_pud;
+
pmd = pmd_alloc(mm, pud, proc);
if (!pmd)
goto out_pmd;
@@ -44,6 +50,8 @@ static int init_stub_pte(struct mm_struc
pmd_free(mm, pmd);
out_pmd:
pud_free(mm, pud);
+ out_pud:
+ p4d_free(mm, p4d);
out:
return -ENOMEM;
}
--- a/arch/um/kernel/skas/uaccess.c~um-add-support-for-folded-p4d-page-tables
+++ a/arch/um/kernel/skas/uaccess.c
@@ -17,6 +17,7 @@
pte_t *virt_to_pte(struct mm_struct *mm, unsigned long addr)
{
pgd_t *pgd;
+ p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;

@@ -27,7 +28,11 @@ pte_t *virt_to_pte(struct mm_struct *mm,
if (!pgd_present(*pgd))
return NULL;

- pud = pud_offset(pgd, addr);
+ p4d = p4d_offset(pgd, addr);
+ if (!p4d_present(*p4d))
+ return NULL;
+
+ pud = pud_offset(p4d, addr);
if (!pud_present(*pud))
return NULL;

--- a/arch/um/kernel/tlb.c~um-add-support-for-folded-p4d-page-tables
+++ a/arch/um/kernel/tlb.c
@@ -277,7 +277,7 @@ static inline int update_pmd_range(pud_t
return ret;
}

-static inline int update_pud_range(pgd_t *pgd, unsigned long addr,
+static inline int update_pud_range(p4d_t *p4d, unsigned long addr,
unsigned long end,
struct host_vm_change *hvc)
{
@@ -285,7 +285,7 @@ static inline int update_pud_range(pgd_t
unsigned long next;
int ret = 0;

- pud = pud_offset(pgd, addr);
+ pud = pud_offset(p4d, addr);
do {
next = pud_addr_end(addr, end);
if (!pud_present(*pud)) {
@@ -299,6 +299,28 @@ static inline int update_pud_range(pgd_t
return ret;
}

+static inline int update_p4d_range(pgd_t *pgd, unsigned long addr,
+ unsigned long end,
+ struct host_vm_change *hvc)
+{
+ p4d_t *p4d;
+ unsigned long next;
+ int ret = 0;
+
+ p4d = p4d_offset(pgd, addr);
+ do {
+ next = p4d_addr_end(addr, end);
+ if (!p4d_present(*p4d)) {
+ if (hvc->force || p4d_newpage(*p4d)) {
+ ret = add_munmap(addr, next - addr, hvc);
+ p4d_mkuptodate(*p4d);
+ }
+ } else
+ ret = update_pud_range(p4d, addr, next, hvc);
+ } while (p4d++, addr = next, ((addr < end) && !ret));
+ return ret;
+}
+
void fix_range_common(struct mm_struct *mm, unsigned long start_addr,
unsigned long end_addr, int force)
{
@@ -316,8 +338,8 @@ void fix_range_common(struct mm_struct *
ret = add_munmap(addr, next - addr, &hvc);
pgd_mkuptodate(*pgd);
}
- }
- else ret = update_pud_range(pgd, addr, next, &hvc);
+ } else
+ ret = update_p4d_range(pgd, addr, next, &hvc);
} while (pgd++, addr = next, ((addr < end_addr) && !ret));

if (!ret)
@@ -338,6 +360,7 @@ static int flush_tlb_kernel_range_common
{
struct mm_struct *mm;
pgd_t *pgd;
+ p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
@@ -364,7 +387,23 @@ static int flush_tlb_kernel_range_common
continue;
}

- pud = pud_offset(pgd, addr);
+ p4d = p4d_offset(pgd, addr);
+ if (!p4d_present(*p4d)) {
+ last = ADD_ROUND(addr, P4D_SIZE);
+ if (last > end)
+ last = end;
+ if (p4d_newpage(*p4d)) {
+ updated = 1;
+ err = add_munmap(addr, last - addr, &hvc);
+ if (err < 0)
+ panic("munmap failed, errno = %d\n",
+ -err);
+ }
+ addr = last;
+ continue;
+ }
+
+ pud = pud_offset(p4d, addr);
if (!pud_present(*pud)) {
last = ADD_ROUND(addr, PUD_SIZE);
if (last > end)
@@ -424,6 +463,7 @@ static int flush_tlb_kernel_range_common
void flush_tlb_page(struct vm_area_struct *vma, unsigned long address)
{
pgd_t *pgd;
+ p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
@@ -437,7 +477,11 @@ void flush_tlb_page(struct vm_area_struc
if (!pgd_present(*pgd))
goto kill;

- pud = pud_offset(pgd, address);
+ p4d = p4d_offset(pgd, address);
+ if (!p4d_present(*p4d))
+ goto kill;
+
+ pud = pud_offset(p4d, address);
if (!pud_present(*pud))
goto kill;

--- a/arch/um/kernel/trap.c~um-add-support-for-folded-p4d-page-tables
+++ a/arch/um/kernel/trap.c
@@ -28,6 +28,7 @@ int handle_page_fault(unsigned long addr
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
pgd_t *pgd;
+ p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
@@ -104,7 +105,8 @@ good_area:
}

pgd = pgd_offset(mm, address);
- pud = pud_offset(pgd, address);
+ p4d = p4d_offset(pgd, address);
+ pud = pud_offset(p4d, address);
pmd = pmd_offset(pud, address);
pte = pte_offset_kernel(pmd, address);
} while (!pte_present(*pte));
_