[PATCH 1/3] powerpc: Define empty_zero_page[] in C

[PATCH 1/3] powerpc: Define empty_zero_page[] in C

[Christophe Leroy]

At the time being, empty_zero_page[] is defined in each
platform head.S.

Define it in mm/mem.c instead, and put it in BSS section instead
of the DATA section. Commit 5227cfa71f9e ("arm64: mm: place
empty_zero_page in bss") explains why it is interesting to have
it in BSS.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
Applies on top of powerpc next-test with the Fixup for v3 "powerpc/nohash: Refactor update of BDI2000 pointers in switch_mmu_context()".
The last patch of this small series can be applied independently at the cost of a trivial conflict in asm-offsets.c

 arch/powerpc/kernel/head_40x.S       | 4 ----
 arch/powerpc/kernel/head_44x.S       | 4 ----
 arch/powerpc/kernel/head_64.S        | 5 -----
 arch/powerpc/kernel/head_8xx.S       | 6 ------
 arch/powerpc/kernel/head_book3s_32.S | 5 -----
 arch/powerpc/kernel/head_fsl_booke.S | 4 ----
 arch/powerpc/mm/mem.c                | 3 +++
 7 files changed, 3 insertions(+), 28 deletions(-)

diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
index 2717aa860cae..92b6c7356161 100644
--- a/arch/powerpc/kernel/head_40x.S
+++ b/arch/powerpc/kernel/head_40x.S
@@ -709,10 +709,6 @@ _GLOBAL(abort)
 	.align	12
 	.globl	sdata
 sdata:
-	.globl	empty_zero_page
-empty_zero_page:
-	.space	4096
-EXPORT_SYMBOL(empty_zero_page)
 	.globl	swapper_pg_dir
 swapper_pg_dir:
 	.space	PGD_TABLE_SIZE
diff --git a/arch/powerpc/kernel/head_44x.S b/arch/powerpc/kernel/head_44x.S
index 2c4ffec027a2..e037eb615757 100644
--- a/arch/powerpc/kernel/head_44x.S
+++ b/arch/powerpc/kernel/head_44x.S
@@ -1241,10 +1241,6 @@ head_start_common:
 	.align	PAGE_SHIFT
 	.globl	sdata
 sdata:
-	.globl	empty_zero_page
-empty_zero_page:
-	.space	PAGE_SIZE
-EXPORT_SYMBOL(empty_zero_page)
 
 /*
  * To support >32-bit physical addresses, we use an 8KB pgdir.
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index ece7f97bafff..730838c7ca39 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -1012,8 +1012,3 @@ start_here_common:
 	.globl	swapper_pg_dir
 swapper_pg_dir:
 	.space	PGD_TABLE_SIZE
-
-	.globl	empty_zero_page
-empty_zero_page:
-	.space	PAGE_SIZE
-EXPORT_SYMBOL(empty_zero_page)
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 817df9fe7fb3..5ce42dfac061 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -795,12 +795,6 @@ _GLOBAL(mmu_pin_tlb)
 	.data
 	.globl	sdata
 sdata:
-	.globl	empty_zero_page
-	.align	PAGE_SHIFT
-empty_zero_page:
-	.space	PAGE_SIZE
-EXPORT_SYMBOL(empty_zero_page)
-
 	.globl	swapper_pg_dir
 swapper_pg_dir:
 	.space	PGD_TABLE_SIZE
diff --git a/arch/powerpc/kernel/head_book3s_32.S b/arch/powerpc/kernel/head_book3s_32.S
index 326262030279..79c744afc6b6 100644
--- a/arch/powerpc/kernel/head_book3s_32.S
+++ b/arch/powerpc/kernel/head_book3s_32.S
@@ -1274,11 +1274,6 @@ setup_usbgecko_bat:
 	.data
 	.globl	sdata
 sdata:
-	.globl	empty_zero_page
-empty_zero_page:
-	.space	4096
-EXPORT_SYMBOL(empty_zero_page)
-
 	.globl	swapper_pg_dir
 swapper_pg_dir:
 	.space	PGD_TABLE_SIZE
diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
index ab718fd5e2a2..f33bc5a8e73e 100644
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -1221,10 +1221,6 @@ _GLOBAL(restore_to_as0)
 	.align	12
 	.globl	sdata
 sdata:
-	.globl	empty_zero_page
-empty_zero_page:
-	.space	4096
-EXPORT_SYMBOL(empty_zero_page)
 	.globl	swapper_pg_dir
 swapper_pg_dir:
 	.space	PGD_TABLE_SIZE
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 043bbeaf407c..b06e5d969051 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -27,6 +27,9 @@
 unsigned long long memory_limit;
 bool init_mem_is_free;
 
+unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
+EXPORT_SYMBOL(empty_zero_page);
+
 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 			      unsigned long size, pgprot_t vma_prot)
 {
-- 
2.25.0

[PATCH 2/3] powerpc: Define swapper_pg_dir[] in C

[Christophe Leroy]

Don't duplicate swapper_pg_dir[] in each platform's head.S

Define it in mm/pgtable.c

Define MAX_PTRS_PER_PGD because on book3s/64 PTRS_PER_PGD is
not a constant.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/include/asm/book3s/64/pgtable.h |  3 +++
 arch/powerpc/include/asm/pgtable.h           |  4 ++++
 arch/powerpc/kernel/asm-offsets.c            |  5 -----
 arch/powerpc/kernel/head_40x.S               | 11 -----------
 arch/powerpc/kernel/head_44x.S               | 17 +----------------
 arch/powerpc/kernel/head_64.S                | 15 ---------------
 arch/powerpc/kernel/head_8xx.S               | 12 ------------
 arch/powerpc/kernel/head_book3s_32.S         | 11 -----------
 arch/powerpc/kernel/head_fsl_booke.S         | 12 ------------
 arch/powerpc/mm/pgtable.c                    |  2 ++
 10 files changed, 10 insertions(+), 82 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index a666d561b44d..4d9941b2fe51 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -232,6 +232,9 @@ extern unsigned long __pmd_frag_size_shift;
 #define PTRS_PER_PUD	(1 << PUD_INDEX_SIZE)
 #define PTRS_PER_PGD	(1 << PGD_INDEX_SIZE)
 
+#define MAX_PTRS_PER_PGD	(1 << (H_PGD_INDEX_SIZE > RADIX_PGD_INDEX_SIZE ? \
+				       H_PGD_INDEX_SIZE : RADIX_PGD_INDEX_SIZE))
+
 /* PMD_SHIFT determines what a second-level page table entry can map */
 #define PMD_SHIFT	(PAGE_SHIFT + PTE_INDEX_SIZE)
 #define PMD_SIZE	(1UL << PMD_SHIFT)
diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index c6a676714f04..b9c8641654f4 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -41,6 +41,10 @@ struct mm_struct;
 
 #ifndef __ASSEMBLY__
 
+#ifndef MAX_PTRS_PER_PGD
+#define MAX_PTRS_PER_PGD PTRS_PER_PGD
+#endif
+
 /* Keep these as a macros to avoid include dependency mess */
 #define pte_page(x)		pfn_to_page(pte_pfn(x))
 #define mk_pte(page, pgprot)	pfn_pte(page_to_pfn(page), (pgprot))
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 0480f4006e0c..f1b6ff14c8a0 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -361,11 +361,6 @@ int main(void)
 	DEFINE(BUG_ENTRY_SIZE, sizeof(struct bug_entry));
 #endif
 
-#ifdef CONFIG_PPC_BOOK3S_64
-	DEFINE(PGD_TABLE_SIZE, (sizeof(pgd_t) << max(RADIX_PGD_INDEX_SIZE, H_PGD_INDEX_SIZE)));
-#else
-	DEFINE(PGD_TABLE_SIZE, PGD_TABLE_SIZE);
-#endif
 	DEFINE(PTE_SIZE, sizeof(pte_t));
 
 #ifdef CONFIG_KVM
diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
index 92b6c7356161..7d72ee5ab387 100644
--- a/arch/powerpc/kernel/head_40x.S
+++ b/arch/powerpc/kernel/head_40x.S
@@ -701,14 +701,3 @@ _GLOBAL(abort)
         mfspr   r13,SPRN_DBCR0
         oris    r13,r13,DBCR0_RST_SYSTEM@h
         mtspr   SPRN_DBCR0,r13
-
-/* We put a few things here that have to be page-aligned. This stuff
- * goes at the beginning of the data segment, which is page-aligned.
- */
-	.data
-	.align	12
-	.globl	sdata
-sdata:
-	.globl	swapper_pg_dir
-swapper_pg_dir:
-	.space	PGD_TABLE_SIZE
diff --git a/arch/powerpc/kernel/head_44x.S b/arch/powerpc/kernel/head_44x.S
index e037eb615757..ddc978a2d381 100644
--- a/arch/powerpc/kernel/head_44x.S
+++ b/arch/powerpc/kernel/head_44x.S
@@ -1233,23 +1233,8 @@ head_start_common:
 	isync
 	blr
 
-/*
- * We put a few things here that have to be page-aligned. This stuff
- * goes at the beginning of the data segment, which is page-aligned.
- */
-	.data
-	.align	PAGE_SHIFT
-	.globl	sdata
-sdata:
-
-/*
- * To support >32-bit physical addresses, we use an 8KB pgdir.
- */
-	.globl	swapper_pg_dir
-swapper_pg_dir:
-	.space	PGD_TABLE_SIZE
-
 #ifdef CONFIG_SMP
+	.data
 	.align	12
 temp_boot_stack:
 	.space	1024
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 730838c7ca39..79f2d1e61abd 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -997,18 +997,3 @@ start_here_common:
 0:	trap
 	EMIT_BUG_ENTRY 0b, __FILE__, __LINE__, 0
 	.previous
-
-/*
- * We put a few things here that have to be page-aligned.
- * This stuff goes at the beginning of the bss, which is page-aligned.
- */
-	.section ".bss"
-/*
- * pgd dir should be aligned to PGD_TABLE_SIZE which is 64K.
- * We will need to find a better way to fix this
- */
-	.align	16
-
-	.globl	swapper_pg_dir
-swapper_pg_dir:
-	.space	PGD_TABLE_SIZE
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 5ce42dfac061..9bdb95f5694f 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -786,15 +786,3 @@ _GLOBAL(mmu_pin_tlb)
 	mtspr	SPRN_SRR1, r10
 	mtspr	SPRN_SRR0, r11
 	rfi
-
-/*
- * We put a few things here that have to be page-aligned.
- * This stuff goes at the beginning of the data segment,
- * which is page-aligned.
- */
-	.data
-	.globl	sdata
-sdata:
-	.globl	swapper_pg_dir
-swapper_pg_dir:
-	.space	PGD_TABLE_SIZE
diff --git a/arch/powerpc/kernel/head_book3s_32.S b/arch/powerpc/kernel/head_book3s_32.S
index 79c744afc6b6..689c9d37f193 100644
--- a/arch/powerpc/kernel/head_book3s_32.S
+++ b/arch/powerpc/kernel/head_book3s_32.S
@@ -1266,18 +1266,7 @@ setup_usbgecko_bat:
 	blr
 #endif
 
-/*
- * We put a few things here that have to be page-aligned.
- * This stuff goes at the beginning of the data segment,
- * which is page-aligned.
- */
 	.data
-	.globl	sdata
-sdata:
-	.globl	swapper_pg_dir
-swapper_pg_dir:
-	.space	PGD_TABLE_SIZE
-
 /* Room for two PTE pointers, usually the kernel and current user pointers
  * to their respective root page table.
  */
diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
index f33bc5a8e73e..0f9642f36b49 100644
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -1212,15 +1212,3 @@ _GLOBAL(restore_to_as0)
 	*/
 3:	mr	r3,r5
 	bl	_start
-
-/*
- * We put a few things here that have to be page-aligned. This stuff
- * goes at the beginning of the data segment, which is page-aligned.
- */
-	.data
-	.align	12
-	.globl	sdata
-sdata:
-	.globl	swapper_pg_dir
-swapper_pg_dir:
-	.space	PGD_TABLE_SIZE
diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index 354611940118..1707ab580ee2 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -28,6 +28,8 @@
 #include <asm/hugetlb.h>
 #include <asm/pte-walk.h>
 
+pgd_t swapper_pg_dir[MAX_PTRS_PER_PGD] __page_aligned_bss;
+
 static inline int is_exec_fault(void)
 {
 	return current->thread.regs && TRAP(current->thread.regs) == 0x400;
-- 
2.25.0

[PATCH 3/3] powerpc/32s: Rename PTE_SIZE to PTE_T_SIZE

[Christophe Leroy]

PTE_SIZE means PTE page table size in most placed, whereas
in hash_low.S in means size of one entry in the table.

Rename it PTE_T_SIZE, and define it directly in hash_low.S
instead of going through asm-offsets.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/kernel/asm-offsets.c   | 2 --
 arch/powerpc/mm/book3s32/hash_low.S | 6 ++++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index f1b6ff14c8a0..2bd936ebcae8 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -361,8 +361,6 @@ int main(void)
 	DEFINE(BUG_ENTRY_SIZE, sizeof(struct bug_entry));
 #endif
 
-	DEFINE(PTE_SIZE, sizeof(pte_t));
-
 #ifdef CONFIG_KVM
 	OFFSET(VCPU_HOST_STACK, kvm_vcpu, arch.host_stack);
 	OFFSET(VCPU_HOST_PID, kvm_vcpu, arch.host_pid);
diff --git a/arch/powerpc/mm/book3s32/hash_low.S b/arch/powerpc/mm/book3s32/hash_low.S
index fb4233a5bdf7..6925ce998557 100644
--- a/arch/powerpc/mm/book3s32/hash_low.S
+++ b/arch/powerpc/mm/book3s32/hash_low.S
@@ -27,8 +27,10 @@
 #include <asm/code-patching-asm.h>
 
 #ifdef CONFIG_PTE_64BIT
+#define PTE_T_SIZE		8
 #define PTE_FLAGS_OFFSET	4	/* offset of PTE flags, in bytes */
 #else
+#define PTE_T_SIZE		4
 #define PTE_FLAGS_OFFSET	0
 #endif
 
@@ -488,7 +490,7 @@ _GLOBAL(flush_hash_pages)
 	bne	2f
 	ble	cr1,19f
 	addi	r4,r4,0x1000
-	addi	r5,r5,PTE_SIZE
+	addi	r5,r5,PTE_T_SIZE
 	addi	r6,r6,-1
 	b	1b
 
@@ -573,7 +575,7 @@ _GLOBAL(flush_hash_pages)
 
 8:	ble	cr1,9f			/* if all ptes checked */
 81:	addi	r6,r6,-1
-	addi	r5,r5,PTE_SIZE
+	addi	r5,r5,PTE_T_SIZE
 	addi	r4,r4,0x1000
 	lwz	r0,0(r5)		/* check next pte */
 	cmpwi	cr1,r6,1
-- 
2.25.0

Re: [PATCH 1/3] powerpc: Define empty_zero_page[] in C

[Michael Ellerman]

On Mon, 7 Jun 2021 10:56:04 +0000 (UTC), Christophe Leroy wrote:
> At the time being, empty_zero_page[] is defined in each
> platform head.S.
> 
> Define it in mm/mem.c instead, and put it in BSS section instead
> of the DATA section. Commit 5227cfa71f9e ("arm64: mm: place
> empty_zero_page in bss") explains why it is interesting to have
> it in BSS.

Applied to powerpc/next.

[1/3] powerpc: Define empty_zero_page[] in C
      https://git.kernel.org/powerpc/c/45b30fafe528601f1a4449c9d68d8ebe7bbc39ad
[2/3] powerpc: Define swapper_pg_dir[] in C
      https://git.kernel.org/powerpc/c/e72421a085a8dc81c71b0daeb89612279c2c621c
[3/3] powerpc/32s: Rename PTE_SIZE to PTE_T_SIZE
      https://git.kernel.org/powerpc/c/91e9ee7e949bff08cc3845a4811185e826b6e2f1

cheers

Re: [PATCH 2/3] powerpc: Define swapper_pg_dir[] in C

[Daniel Axtens]

Hi Christophe,

This breaks booting a radix KVM guest with 4k pages for me:

make pseries_le_defconfig
scripts/config -d CONFIG_PPC_64K_PAGES
scripts/config -e CONFIG_PPC_4K_PAGES
make vmlinux
sudo qemu-system-ppc64 -enable-kvm -M pseries -m 1G -nographic -vga none -smp 4 -cpu host -kernel vmlinux

Boot hangs after printing 'Booting Linux via __start()' and qemu's 'info
registers' reports that it's stuck at the instruction fetch exception.

My host is Power9, 64k page size radix, and
gcc (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0, GNU ld (GNU Binutils for Ubuntu) 2.34

Kind regards,
Daniel

> Don't duplicate swapper_pg_dir[] in each platform's head.S
>
> Define it in mm/pgtable.c
>
> Define MAX_PTRS_PER_PGD because on book3s/64 PTRS_PER_PGD is
> not a constant.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/powerpc/include/asm/book3s/64/pgtable.h |  3 +++
>  arch/powerpc/include/asm/pgtable.h           |  4 ++++
>  arch/powerpc/kernel/asm-offsets.c            |  5 -----
>  arch/powerpc/kernel/head_40x.S               | 11 -----------
>  arch/powerpc/kernel/head_44x.S               | 17 +----------------
>  arch/powerpc/kernel/head_64.S                | 15 ---------------
>  arch/powerpc/kernel/head_8xx.S               | 12 ------------
>  arch/powerpc/kernel/head_book3s_32.S         | 11 -----------
>  arch/powerpc/kernel/head_fsl_booke.S         | 12 ------------
>  arch/powerpc/mm/pgtable.c                    |  2 ++
>  10 files changed, 10 insertions(+), 82 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
> index a666d561b44d..4d9941b2fe51 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
> @@ -232,6 +232,9 @@ extern unsigned long __pmd_frag_size_shift;
>  #define PTRS_PER_PUD	(1 << PUD_INDEX_SIZE)
>  #define PTRS_PER_PGD	(1 << PGD_INDEX_SIZE)
>  
> +#define MAX_PTRS_PER_PGD	(1 << (H_PGD_INDEX_SIZE > RADIX_PGD_INDEX_SIZE ? \
> +				       H_PGD_INDEX_SIZE : RADIX_PGD_INDEX_SIZE))
> +
>  /* PMD_SHIFT determines what a second-level page table entry can map */
>  #define PMD_SHIFT	(PAGE_SHIFT + PTE_INDEX_SIZE)
>  #define PMD_SIZE	(1UL << PMD_SHIFT)
> diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
> index c6a676714f04..b9c8641654f4 100644
> --- a/arch/powerpc/include/asm/pgtable.h
> +++ b/arch/powerpc/include/asm/pgtable.h
> @@ -41,6 +41,10 @@ struct mm_struct;
>  
>  #ifndef __ASSEMBLY__
>  
> +#ifndef MAX_PTRS_PER_PGD
> +#define MAX_PTRS_PER_PGD PTRS_PER_PGD
> +#endif
> +
>  /* Keep these as a macros to avoid include dependency mess */
>  #define pte_page(x)		pfn_to_page(pte_pfn(x))
>  #define mk_pte(page, pgprot)	pfn_pte(page_to_pfn(page), (pgprot))
> diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
> index 0480f4006e0c..f1b6ff14c8a0 100644
> --- a/arch/powerpc/kernel/asm-offsets.c
> +++ b/arch/powerpc/kernel/asm-offsets.c
> @@ -361,11 +361,6 @@ int main(void)
>  	DEFINE(BUG_ENTRY_SIZE, sizeof(struct bug_entry));
>  #endif
>  
> -#ifdef CONFIG_PPC_BOOK3S_64
> -	DEFINE(PGD_TABLE_SIZE, (sizeof(pgd_t) << max(RADIX_PGD_INDEX_SIZE, H_PGD_INDEX_SIZE)));
> -#else
> -	DEFINE(PGD_TABLE_SIZE, PGD_TABLE_SIZE);
> -#endif
>  	DEFINE(PTE_SIZE, sizeof(pte_t));
>  
>  #ifdef CONFIG_KVM
> diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
> index 92b6c7356161..7d72ee5ab387 100644
> --- a/arch/powerpc/kernel/head_40x.S
> +++ b/arch/powerpc/kernel/head_40x.S
> @@ -701,14 +701,3 @@ _GLOBAL(abort)
>          mfspr   r13,SPRN_DBCR0
>          oris    r13,r13,DBCR0_RST_SYSTEM@h
>          mtspr   SPRN_DBCR0,r13
> -
> -/* We put a few things here that have to be page-aligned. This stuff
> - * goes at the beginning of the data segment, which is page-aligned.
> - */
> -	.data
> -	.align	12
> -	.globl	sdata
> -sdata:
> -	.globl	swapper_pg_dir
> -swapper_pg_dir:
> -	.space	PGD_TABLE_SIZE
> diff --git a/arch/powerpc/kernel/head_44x.S b/arch/powerpc/kernel/head_44x.S
> index e037eb615757..ddc978a2d381 100644
> --- a/arch/powerpc/kernel/head_44x.S
> +++ b/arch/powerpc/kernel/head_44x.S
> @@ -1233,23 +1233,8 @@ head_start_common:
>  	isync
>  	blr
>  
> -/*
> - * We put a few things here that have to be page-aligned. This stuff
> - * goes at the beginning of the data segment, which is page-aligned.
> - */
> -	.data
> -	.align	PAGE_SHIFT
> -	.globl	sdata
> -sdata:
> -
> -/*
> - * To support >32-bit physical addresses, we use an 8KB pgdir.
> - */
> -	.globl	swapper_pg_dir
> -swapper_pg_dir:
> -	.space	PGD_TABLE_SIZE
> -
>  #ifdef CONFIG_SMP
> +	.data
>  	.align	12
>  temp_boot_stack:
>  	.space	1024
> diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
> index 730838c7ca39..79f2d1e61abd 100644
> --- a/arch/powerpc/kernel/head_64.S
> +++ b/arch/powerpc/kernel/head_64.S
> @@ -997,18 +997,3 @@ start_here_common:
>  0:	trap
>  	EMIT_BUG_ENTRY 0b, __FILE__, __LINE__, 0
>  	.previous
> -
> -/*
> - * We put a few things here that have to be page-aligned.
> - * This stuff goes at the beginning of the bss, which is page-aligned.
> - */
> -	.section ".bss"
> -/*
> - * pgd dir should be aligned to PGD_TABLE_SIZE which is 64K.
> - * We will need to find a better way to fix this
> - */
> -	.align	16
> -
> -	.globl	swapper_pg_dir
> -swapper_pg_dir:
> -	.space	PGD_TABLE_SIZE
> diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
> index 5ce42dfac061..9bdb95f5694f 100644
> --- a/arch/powerpc/kernel/head_8xx.S
> +++ b/arch/powerpc/kernel/head_8xx.S
> @@ -786,15 +786,3 @@ _GLOBAL(mmu_pin_tlb)
>  	mtspr	SPRN_SRR1, r10
>  	mtspr	SPRN_SRR0, r11
>  	rfi
> -
> -/*
> - * We put a few things here that have to be page-aligned.
> - * This stuff goes at the beginning of the data segment,
> - * which is page-aligned.
> - */
> -	.data
> -	.globl	sdata
> -sdata:
> -	.globl	swapper_pg_dir
> -swapper_pg_dir:
> -	.space	PGD_TABLE_SIZE
> diff --git a/arch/powerpc/kernel/head_book3s_32.S b/arch/powerpc/kernel/head_book3s_32.S
> index 79c744afc6b6..689c9d37f193 100644
> --- a/arch/powerpc/kernel/head_book3s_32.S
> +++ b/arch/powerpc/kernel/head_book3s_32.S
> @@ -1266,18 +1266,7 @@ setup_usbgecko_bat:
>  	blr
>  #endif
>  
> -/*
> - * We put a few things here that have to be page-aligned.
> - * This stuff goes at the beginning of the data segment,
> - * which is page-aligned.
> - */
>  	.data
> -	.globl	sdata
> -sdata:
> -	.globl	swapper_pg_dir
> -swapper_pg_dir:
> -	.space	PGD_TABLE_SIZE
> -
>  /* Room for two PTE pointers, usually the kernel and current user pointers
>   * to their respective root page table.
>   */
> diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
> index f33bc5a8e73e..0f9642f36b49 100644
> --- a/arch/powerpc/kernel/head_fsl_booke.S
> +++ b/arch/powerpc/kernel/head_fsl_booke.S
> @@ -1212,15 +1212,3 @@ _GLOBAL(restore_to_as0)
>  	*/
>  3:	mr	r3,r5
>  	bl	_start
> -
> -/*
> - * We put a few things here that have to be page-aligned. This stuff
> - * goes at the beginning of the data segment, which is page-aligned.
> - */
> -	.data
> -	.align	12
> -	.globl	sdata
> -sdata:
> -	.globl	swapper_pg_dir
> -swapper_pg_dir:
> -	.space	PGD_TABLE_SIZE
> diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
> index 354611940118..1707ab580ee2 100644
> --- a/arch/powerpc/mm/pgtable.c
> +++ b/arch/powerpc/mm/pgtable.c
> @@ -28,6 +28,8 @@
>  #include <asm/hugetlb.h>
>  #include <asm/pte-walk.h>
>  
> +pgd_t swapper_pg_dir[MAX_PTRS_PER_PGD] __page_aligned_bss;
> +
>  static inline int is_exec_fault(void)
>  {
>  	return current->thread.regs && TRAP(current->thread.regs) == 0x400;
> -- 
> 2.25.0

Re: [PATCH 2/3] powerpc: Define swapper_pg_dir[] in C

[Michael Ellerman]

Daniel Axtens <dja@axtens.net> writes:
> Hi Christophe,
>
> This breaks booting a radix KVM guest with 4k pages for me:
>
> make pseries_le_defconfig
> scripts/config -d CONFIG_PPC_64K_PAGES
> scripts/config -e CONFIG_PPC_4K_PAGES
> make vmlinux
> sudo qemu-system-ppc64 -enable-kvm -M pseries -m 1G -nographic -vga none -smp 4 -cpu host -kernel vmlinux
>
> Boot hangs after printing 'Booting Linux via __start()' and qemu's 'info
> registers' reports that it's stuck at the instruction fetch exception.
>
> My host is Power9, 64k page size radix, and
> gcc (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0, GNU ld (GNU Binutils for Ubuntu) 2.34
>

...
>> diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
>> index 730838c7ca39..79f2d1e61abd 100644
>> --- a/arch/powerpc/kernel/head_64.S
>> +++ b/arch/powerpc/kernel/head_64.S
>> @@ -997,18 +997,3 @@ start_here_common:
>>  0:	trap
>>  	EMIT_BUG_ENTRY 0b, __FILE__, __LINE__, 0
>>  	.previous
>> -
>> -/*
>> - * We put a few things here that have to be page-aligned.
>> - * This stuff goes at the beginning of the bss, which is page-aligned.
>> - */
>> -	.section ".bss"
>> -/*
>> - * pgd dir should be aligned to PGD_TABLE_SIZE which is 64K.
>> - * We will need to find a better way to fix this
>> - */
>> -	.align	16
>> -
>> -	.globl	swapper_pg_dir
>> -swapper_pg_dir:
>> -	.space	PGD_TABLE_SIZE

This is now 4K aligned whereas it used to be 64K.

This fixes it and is not completely ugly?

diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index 1707ab580ee2..298469beaa90 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -28,7 +28,13 @@
 #include <asm/hugetlb.h>
 #include <asm/pte-walk.h>
 
-pgd_t swapper_pg_dir[MAX_PTRS_PER_PGD] __page_aligned_bss;
+#ifdef CONFIG_PPC64
+#define PGD_ALIGN 0x10000
+#else
+#define PGD_ALIGN PAGE_SIZE
+#endif
+
+pgd_t swapper_pg_dir[MAX_PTRS_PER_PGD] __section(".bss..page_aligned") __aligned(PGD_ALIGN);
 
 static inline int is_exec_fault(void)
 {


cheers

Re: [PATCH 2/3] powerpc: Define swapper_pg_dir[] in C

[Daniel Axtens]

Michael Ellerman <mpe@ellerman.id.au> writes:

> Daniel Axtens <dja@axtens.net> writes:
>> Hi Christophe,
>>
>> This breaks booting a radix KVM guest with 4k pages for me:
>>
>> make pseries_le_defconfig
>> scripts/config -d CONFIG_PPC_64K_PAGES
>> scripts/config -e CONFIG_PPC_4K_PAGES
>> make vmlinux
>> sudo qemu-system-ppc64 -enable-kvm -M pseries -m 1G -nographic -vga none -smp 4 -cpu host -kernel vmlinux
>>
>> Boot hangs after printing 'Booting Linux via __start()' and qemu's 'info
>> registers' reports that it's stuck at the instruction fetch exception.
>>
>> My host is Power9, 64k page size radix, and
>> gcc (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0, GNU ld (GNU Binutils for Ubuntu) 2.34
>>
>
> ...
>>> diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
>>> index 730838c7ca39..79f2d1e61abd 100644
>>> --- a/arch/powerpc/kernel/head_64.S
>>> +++ b/arch/powerpc/kernel/head_64.S
>>> @@ -997,18 +997,3 @@ start_here_common:
>>>  0:	trap
>>>  	EMIT_BUG_ENTRY 0b, __FILE__, __LINE__, 0
>>>  	.previous
>>> -
>>> -/*
>>> - * We put a few things here that have to be page-aligned.
>>> - * This stuff goes at the beginning of the bss, which is page-aligned.
>>> - */
>>> -	.section ".bss"
>>> -/*
>>> - * pgd dir should be aligned to PGD_TABLE_SIZE which is 64K.
>>> - * We will need to find a better way to fix this
>>> - */
>>> -	.align	16
>>> -
>>> -	.globl	swapper_pg_dir
>>> -swapper_pg_dir:
>>> -	.space	PGD_TABLE_SIZE
>
> This is now 4K aligned whereas it used to be 64K.
>
> This fixes it and is not completely ugly?
>
> diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
> index 1707ab580ee2..298469beaa90 100644
> --- a/arch/powerpc/mm/pgtable.c
> +++ b/arch/powerpc/mm/pgtable.c
> @@ -28,7 +28,13 @@
>  #include <asm/hugetlb.h>
>  #include <asm/pte-walk.h>
>  
> -pgd_t swapper_pg_dir[MAX_PTRS_PER_PGD] __page_aligned_bss;
> +#ifdef CONFIG_PPC64
> +#define PGD_ALIGN 0x10000
> +#else
> +#define PGD_ALIGN PAGE_SIZE
> +#endif
> +
> +pgd_t swapper_pg_dir[MAX_PTRS_PER_PGD] __section(".bss..page_aligned") __aligned(PGD_ALIGN);

The fix works for me, thank you.

Kind regards,
Daniel
>  
>  static inline int is_exec_fault(void)
>  {
>
>
> cheers