diff mbox series

[v3,05/60] arm64: mm: Move fixmap region above vmemmap region

Message ID 20230307140522.2311461-6-ardb@kernel.org
State New
Headers
Series arm64: Add support for LPA2 at stage1 and WXN |

Commit Message

Ard Biesheuvel March 7, 2023, 2:04 p.m. UTC 
  Move the fixmap region above the vmemmap region, so that the start of
the vmemmap delineates the end of the region available for vmalloc and
vmap allocations and the randomized placement of the kernel and modules.

In a subsequent patch, we will take advantage of this to reclaim most of
the vmemmap area when running a 52-bit VA capable build with 52-bit
virtual addressing disabled at runtime.

Note that the existing guard region of 256 MiB covers the fixmap and PCI
I/O regions as well, so we can reduce it 8 MiB, which is what we use in
other places too.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/include/asm/memory.h  | 2 +-
 arch/arm64/include/asm/pgtable.h | 2 +-
 arch/arm64/mm/ptdump.c           | 4 ++--
 3 files changed, 4 insertions(+), 4 deletions(-)

Comments

Mark Rutland April 28, 2023, 11 a.m. UTC | #1 
On Tue, Mar 07, 2023 at 03:04:27PM +0100, Ard Biesheuvel wrote:
> Move the fixmap region above the vmemmap region, so that the start of
> the vmemmap delineates the end of the region available for vmalloc and
> vmap allocations and the randomized placement of the kernel and modules.
> 
> In a subsequent patch, we will take advantage of this to reclaim most of
> the vmemmap area when running a 52-bit VA capable build with 52-bit
> virtual addressing disabled at runtime.
> 
> Note that the existing guard region of 256 MiB covers the fixmap and PCI
> I/O regions as well, so we can reduce it 8 MiB, which is what we use in
> other places too.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
>  arch/arm64/include/asm/memory.h  | 2 +-
>  arch/arm64/include/asm/pgtable.h | 2 +-
>  arch/arm64/mm/ptdump.c           | 4 ++--
>  3 files changed, 4 insertions(+), 4 deletions(-)

As a heads-up, this will (trivially) conflict with some of the arm64 fixmap
cleanups that'll be in v6.4-rc1, due to the FIXADDR_TOT_* changes.

> 
> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
> index 6e321cc06a3c30f0..9b9e52d823beccc6 100644
> --- a/arch/arm64/include/asm/memory.h
> +++ b/arch/arm64/include/asm/memory.h
> @@ -51,7 +51,7 @@
>  #define VMEMMAP_END		(VMEMMAP_START + VMEMMAP_SIZE)
>  #define PCI_IO_START		(VMEMMAP_END + SZ_8M)
>  #define PCI_IO_END		(PCI_IO_START + PCI_IO_SIZE)
> -#define FIXADDR_TOP		(VMEMMAP_START - SZ_32M)
> +#define FIXADDR_TOP		(ULONG_MAX - SZ_8M + 1)

Can we make this:

  #define FIXADDR_TOP	(-SZ_8M)

... as that would match the way we define PAGE_OFFSET (and VMEMMAP_START), and
it removes the need for the '+1' to handle ULONG_MAX being one-off what we
actually want to subtact from.

Mark.

>  
>  #if VA_BITS > 48
>  #define VA_BITS_MIN		(48)
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index b6ba466e2e8a3fc7..3eff06c5d0eb73c7 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -22,7 +22,7 @@
>   *	and fixed mappings
>   */
>  #define VMALLOC_START		(MODULES_END)
> -#define VMALLOC_END		(VMEMMAP_START - SZ_256M)
> +#define VMALLOC_END		(VMEMMAP_START - SZ_8M)
>  
>  #define vmemmap			((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT))
>  
> diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
> index 9d1f4cdc6672ed5f..76d28056bd14920a 100644
> --- a/arch/arm64/mm/ptdump.c
> +++ b/arch/arm64/mm/ptdump.c
> @@ -45,12 +45,12 @@ static struct addr_marker address_markers[] = {
>  	{ MODULES_END,			"Modules end" },
>  	{ VMALLOC_START,		"vmalloc() area" },
>  	{ VMALLOC_END,			"vmalloc() end" },
> -	{ FIXADDR_START,		"Fixmap start" },
> -	{ FIXADDR_TOP,			"Fixmap end" },
>  	{ VMEMMAP_START,		"vmemmap start" },
>  	{ VMEMMAP_START + VMEMMAP_SIZE,	"vmemmap end" },
>  	{ PCI_IO_START,			"PCI I/O start" },
>  	{ PCI_IO_END,			"PCI I/O end" },
> +	{ FIXADDR_START,		"Fixmap start" },
> +	{ FIXADDR_TOP,			"Fixmap end" },
>  	{ -1,				NULL },
>  };
>  
> -- 
> 2.39.2
> 
>
diff mbox series

Patch

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 6e321cc06a3c30f0..9b9e52d823beccc6 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -51,7 +51,7 @@ 
 #define VMEMMAP_END		(VMEMMAP_START + VMEMMAP_SIZE)
 #define PCI_IO_START		(VMEMMAP_END + SZ_8M)
 #define PCI_IO_END		(PCI_IO_START + PCI_IO_SIZE)
-#define FIXADDR_TOP		(VMEMMAP_START - SZ_32M)
+#define FIXADDR_TOP		(ULONG_MAX - SZ_8M + 1)
 
 #if VA_BITS > 48
 #define VA_BITS_MIN		(48)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index b6ba466e2e8a3fc7..3eff06c5d0eb73c7 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -22,7 +22,7 @@ 
  *	and fixed mappings
  */
 #define VMALLOC_START		(MODULES_END)
-#define VMALLOC_END		(VMEMMAP_START - SZ_256M)
+#define VMALLOC_END		(VMEMMAP_START - SZ_8M)
 
 #define vmemmap			((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT))
 
diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
index 9d1f4cdc6672ed5f..76d28056bd14920a 100644
--- a/arch/arm64/mm/ptdump.c
+++ b/arch/arm64/mm/ptdump.c
@@ -45,12 +45,12 @@  static struct addr_marker address_markers[] = {
 	{ MODULES_END,			"Modules end" },
 	{ VMALLOC_START,		"vmalloc() area" },
 	{ VMALLOC_END,			"vmalloc() end" },
-	{ FIXADDR_START,		"Fixmap start" },
-	{ FIXADDR_TOP,			"Fixmap end" },
 	{ VMEMMAP_START,		"vmemmap start" },
 	{ VMEMMAP_START + VMEMMAP_SIZE,	"vmemmap end" },
 	{ PCI_IO_START,			"PCI I/O start" },
 	{ PCI_IO_END,			"PCI I/O end" },
+	{ FIXADDR_START,		"Fixmap start" },
+	{ FIXADDR_TOP,			"Fixmap end" },
 	{ -1,				NULL },
 };