diff mbox series

[v2] Revert "mm/pgtable: add stubs for {pmd/pub}_{set/clear}_huge"

Message ID 87r1fs1762.fsf@mpe.ellerman.id.au (mailing list archive)
State New, archived
Headers show
Series [v2] Revert "mm/pgtable: add stubs for {pmd/pub}_{set/clear}_huge" | expand

Commit Message

Michael Ellerman July 21, 2021, 7:02 a.m. UTC 
From: Jonathan Marek <jonathan@marek.ca>

This reverts commit c742199a014de23ee92055c2473d91fe5561ffdf.

c742199a014d ("mm/pgtable: add stubs for {pmd/pub}_{set/clear}_huge")
breaks arm64 in at least two ways for configurations where PUD or PMD
folding occur:

  1. We no longer install huge-vmap mappings and silently fall back to
     page-granular entries, despite being able to install block entries
     at what is effectively the PGD level.

  2. If the linear map is backed with block mappings, these will now
     silently fail to be created in alloc_init_pud(), causing a panic
     early during boot.

The pgtable selftests caught this, although a fix has not been
forthcoming and Christophe is AWOL at the moment, so just revert the
change for now to get a working -rc3 on which we can queue patches for
5.15.

A simple revert breaks the build for 32-bit PowerPC 8xx machines, which
rely on the default function definitions when the corresponding
page-table levels are folded, since commit a6a8f7c4aa7e ("powerpc/8xx:
add support for huge pages on VMAP and VMALLOC"), eg:

  powerpc64-linux-ld: mm/vmalloc.o: in function `vunmap_pud_range':
  linux/mm/vmalloc.c:362: undefined reference to `pud_clear_huge'

To avoid that, add stubs for pud_clear_huge() and pmd_clear_huge() in
arch/powerpc/mm/nohash/8xx.c as suggested by Christophe.

Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Fixes: c742199a014d ("mm/pgtable: add stubs for {pmd/pub}_{set/clear}_huge")
Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Signed-off-by: Will Deacon <will@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Marc Zyngier <maz@kernel.org>
[mpe: Fold in 8xx.c changes from Christophe and mention in change log]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/linux-arm-kernel/CAMuHMdXShORDox-xxaeUfDW3wx2PeggFSqhVSHVZNKCGK-y_vQ@mail.gmail.com/
Link: https://lore.kernel.org/r/20210717160118.9855-1-jonathan@marek.ca
---
 arch/arm64/mm/mmu.c          | 20 ++++++++------------
 arch/powerpc/mm/nohash/8xx.c | 10 ++++++++++
 arch/x86/mm/pgtable.c        | 34 +++++++++++++++-------------------
 include/linux/pgtable.h      | 26 +-------------------------
 4 files changed, 34 insertions(+), 56 deletions(-)

v2: Fold in suggestion from Christophe to add stubs for 8xx.

I kept the reviewed-by/acked-by tags from arm64 folks as the patch is
unchanged as far as arm64 is concerned.

Please take this via the arm64 tree.

cheers

Comments

Will Deacon July 21, 2021, 10:47 a.m. UTC | #1 
On Wed, 21 Jul 2021 17:02:13 +1000, Michael Ellerman wrote:
> This reverts commit c742199a014de23ee92055c2473d91fe5561ffdf.
> 
> c742199a014d ("mm/pgtable: add stubs for {pmd/pub}_{set/clear}_huge")
> breaks arm64 in at least two ways for configurations where PUD or PMD
> folding occur:
> 
>   1. We no longer install huge-vmap mappings and silently fall back to
>      page-granular entries, despite being able to install block entries
>      at what is effectively the PGD level.
> 
> [...]

Thank you Michael! I owe you a beer next time I see you, if we don't go
extinct before then.

Applied to arm64 (for-next/fixes), thanks!

[1/1] Revert "mm/pgtable: add stubs for {pmd/pub}_{set/clear}_huge"
      https://git.kernel.org/arm64/c/d8a719059b9d

Cheers,
Michael Ellerman July 23, 2021, 12:04 p.m. UTC | #2 
Will Deacon <will@kernel.org> writes:
> On Wed, 21 Jul 2021 17:02:13 +1000, Michael Ellerman wrote:
>> This reverts commit c742199a014de23ee92055c2473d91fe5561ffdf.
>> 
>> c742199a014d ("mm/pgtable: add stubs for {pmd/pub}_{set/clear}_huge")
>> breaks arm64 in at least two ways for configurations where PUD or PMD
>> folding occur:
>> 
>>   1. We no longer install huge-vmap mappings and silently fall back to
>>      page-granular entries, despite being able to install block entries
>>      at what is effectively the PGD level.
>> 
>> [...]
>
> Thank you Michael! I owe you a beer next time I see you, if we don't go
> extinct before then.

No worries, thanks to Christophe for identifying the solution while on
vacation!

Beers seem a long way off, but hopefully one day :)

cheers
diff mbox series

Patch

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index d74586508448..9ff0de1b2b93 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1339,7 +1339,6 @@  void *__init fixmap_remap_fdt(phys_addr_t dt_phys, int *size, pgprot_t prot)
 	return dt_virt;
 }
 
-#if CONFIG_PGTABLE_LEVELS > 3
 int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
 {
 	pud_t new_pud = pfn_pud(__phys_to_pfn(phys), mk_pud_sect_prot(prot));
@@ -1354,16 +1353,6 @@  int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
 	return 1;
 }
 
-int pud_clear_huge(pud_t *pudp)
-{
-	if (!pud_sect(READ_ONCE(*pudp)))
-		return 0;
-	pud_clear(pudp);
-	return 1;
-}
-#endif
-
-#if CONFIG_PGTABLE_LEVELS > 2
 int pmd_set_huge(pmd_t *pmdp, phys_addr_t phys, pgprot_t prot)
 {
 	pmd_t new_pmd = pfn_pmd(__phys_to_pfn(phys), mk_pmd_sect_prot(prot));
@@ -1378,6 +1367,14 @@  int pmd_set_huge(pmd_t *pmdp, phys_addr_t phys, pgprot_t prot)
 	return 1;
 }
 
+int pud_clear_huge(pud_t *pudp)
+{
+	if (!pud_sect(READ_ONCE(*pudp)))
+		return 0;
+	pud_clear(pudp);
+	return 1;
+}
+
 int pmd_clear_huge(pmd_t *pmdp)
 {
 	if (!pmd_sect(READ_ONCE(*pmdp)))
@@ -1385,7 +1382,6 @@  int pmd_clear_huge(pmd_t *pmdp)
 	pmd_clear(pmdp);
 	return 1;
 }
-#endif
 
 int pmd_free_pte_page(pmd_t *pmdp, unsigned long addr)
 {
diff --git a/arch/powerpc/mm/nohash/8xx.c b/arch/powerpc/mm/nohash/8xx.c
index 60780e089118..0df9fe29dd56 100644
--- a/arch/powerpc/mm/nohash/8xx.c
+++ b/arch/powerpc/mm/nohash/8xx.c
@@ -240,3 +240,13 @@  void __init setup_kuap(bool disabled)
 	mtspr(SPRN_MD_AP, MD_APG_KUAP);
 }
 #endif
+
+int pud_clear_huge(pud_t *pud)
+{
+	 return 0;
+}
+
+int pmd_clear_huge(pmd_t *pmd)
+{
+	 return 0;
+}
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 3364fe62b903..3481b35cb4ec 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -682,7 +682,6 @@  int p4d_clear_huge(p4d_t *p4d)
 }
 #endif
 
-#if CONFIG_PGTABLE_LEVELS > 3
 /**
  * pud_set_huge - setup kernel PUD mapping
  *
@@ -721,23 +720,6 @@  int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
 	return 1;
 }
 
-/**
- * pud_clear_huge - clear kernel PUD mapping when it is set
- *
- * Returns 1 on success and 0 on failure (no PUD map is found).
- */
-int pud_clear_huge(pud_t *pud)
-{
-	if (pud_large(*pud)) {
-		pud_clear(pud);
-		return 1;
-	}
-
-	return 0;
-}
-#endif
-
-#if CONFIG_PGTABLE_LEVELS > 2
 /**
  * pmd_set_huge - setup kernel PMD mapping
  *
@@ -768,6 +750,21 @@  int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
 	return 1;
 }
 
+/**
+ * pud_clear_huge - clear kernel PUD mapping when it is set
+ *
+ * Returns 1 on success and 0 on failure (no PUD map is found).
+ */
+int pud_clear_huge(pud_t *pud)
+{
+	if (pud_large(*pud)) {
+		pud_clear(pud);
+		return 1;
+	}
+
+	return 0;
+}
+
 /**
  * pmd_clear_huge - clear kernel PMD mapping when it is set
  *
@@ -782,7 +779,6 @@  int pmd_clear_huge(pmd_t *pmd)
 
 	return 0;
 }
-#endif
 
 #ifdef CONFIG_X86_64
 /**
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index d147480cdefc..e24d2c992b11 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1397,34 +1397,10 @@  static inline int p4d_clear_huge(p4d_t *p4d)
 }
 #endif /* !__PAGETABLE_P4D_FOLDED */
 
-#ifndef __PAGETABLE_PUD_FOLDED
 int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot);
-int pud_clear_huge(pud_t *pud);
-#else
-static inline int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
-{
-	return 0;
-}
-static inline int pud_clear_huge(pud_t *pud)
-{
-	return 0;
-}
-#endif /* !__PAGETABLE_PUD_FOLDED */
-
-#ifndef __PAGETABLE_PMD_FOLDED
 int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot);
+int pud_clear_huge(pud_t *pud);
 int pmd_clear_huge(pmd_t *pmd);
-#else
-static inline int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
-{
-	return 0;
-}
-static inline int pmd_clear_huge(pmd_t *pmd)
-{
-	return 0;
-}
-#endif /* !__PAGETABLE_PMD_FOLDED */
-
 int p4d_free_pud_page(p4d_t *p4d, unsigned long addr);
 int pud_free_pmd_page(pud_t *pud, unsigned long addr);
 int pmd_free_pte_page(pmd_t *pmd, unsigned long addr);