diff options
author | Suzuki Poulose <suzuki@in.ibm.com> | 2011-12-14 22:58:37 +0000 |
---|---|---|
committer | Josh Boyer <jwboyer@gmail.com> | 2011-12-20 10:21:34 -0500 |
commit | 368ff8f14d6ed8e9fd3b7c2156f2607719bf5a7a (patch) | |
tree | a52996c9083368fc3c5297bc45d5f67189de9ad7 /arch/powerpc/include | |
parent | 9c5f7d39a86316cd13baf973c90ed27f9f1cc979 (diff) |
powerpc: Define virtual-physical translations for RELOCATABLE
We find the runtime address of _stext and relocate ourselves based
on the following calculation.
virtual_base = ALIGN(KERNELBASE,KERNEL_TLB_PIN_SIZE) +
MODULO(_stext.run,KERNEL_TLB_PIN_SIZE)
relocate() is called with the Effective Virtual Base Address (as
shown below)
| Phys. Addr| Virt. Addr |
Page |------------------------|
Boundary | | |
| | |
| | |
Kernel Load |___________|_ __ _ _ _ _|<- Effective
Addr(_stext)| | ^ |Virt. Base Addr
| | | |
| | | |
| |reloc_offset|
| | | |
| | | |
| |______v_____|<-(KERNELBASE)%TLB_SIZE
| | |
| | |
| | |
Page |-----------|------------|
Boundary | | |
On BookE, we need __va() & __pa() early in the boot process to access
the device tree.
Currently this has been defined as :
#define __va(x) ((void *)(unsigned long)((phys_addr_t)(x) -
PHYSICAL_START + KERNELBASE)
where:
PHYSICAL_START is kernstart_addr - a variable updated at runtime.
KERNELBASE is the compile time Virtual base address of kernel.
This won't work for us, as kernstart_addr is dynamic and will yield different
results for __va()/__pa() for same mapping.
e.g.,
Let the kernel be loaded at 64MB and KERNELBASE be 0xc0000000 (same as
PAGE_OFFSET).
In this case, we would be mapping 0 to 0xc0000000, and kernstart_addr = 64M
Now __va(1MB) = (0x100000) - (0x4000000) + 0xc0000000
= 0xbc100000 , which is wrong.
it should be : 0xc0000000 + 0x100000 = 0xc0100000
On platforms which support AMP, like PPC_47x (based on 44x), the kernel
could be loaded at highmem. Hence we cannot always depend on the compile
time constants for mapping.
Here are the possible solutions:
1) Update kernstart_addr(PHSYICAL_START) to match the Physical address of
compile time KERNELBASE value, instead of the actual Physical_Address(_stext).
The disadvantage is that we may break other users of PHYSICAL_START. They
could be replaced with __pa(_stext).
2) Redefine __va() & __pa() with relocation offset
#ifdef CONFIG_RELOCATABLE_PPC32
#define __va(x) ((void *)(unsigned long)((phys_addr_t)(x) - PHYSICAL_START + (KERNELBASE + RELOC_OFFSET)))
#define __pa(x) ((unsigned long)(x) + PHYSICAL_START - (KERNELBASE + RELOC_OFFSET))
#endif
where, RELOC_OFFSET could be
a) A variable, say relocation_offset (like kernstart_addr), updated
at boot time. This impacts performance, as we have to load an additional
variable from memory.
OR
b) #define RELOC_OFFSET ((PHYSICAL_START & PPC_PIN_SIZE_OFFSET_MASK) - \
(KERNELBASE & PPC_PIN_SIZE_OFFSET_MASK))
This introduces more calculations for doing the translation.
3) Redefine __va() & __pa() with a new variable
i.e,
#define __va(x) ((void *)(unsigned long)((phys_addr_t)(x) + VIRT_PHYS_OFFSET))
where VIRT_PHYS_OFFSET :
#ifdef CONFIG_RELOCATABLE_PPC32
#define VIRT_PHYS_OFFSET virt_phys_offset
#else
#define VIRT_PHYS_OFFSET (KERNELBASE - PHYSICAL_START)
#endif /* CONFIG_RELOCATABLE_PPC32 */
where virt_phy_offset is updated at runtime to :
Effective KERNELBASE - kernstart_addr.
Taking our example, above:
virt_phys_offset = effective_kernelstart_vaddr - kernstart_addr
= 0xc0400000 - 0x400000
= 0xc0000000
and
__va(0x100000) = 0xc0000000 + 0x100000 = 0xc0100000
which is what we want.
I have implemented (3) in the following patch which has same cost of
operation as the existing one.
I have tested the patches on 440x platforms only. However this should
work fine for PPC_47x also, as we only depend on the runtime address
and the current TLB XLAT entry for the startup code, which is available
in r25. I don't have access to a 47x board yet. So, it would be great if
somebody could test this on 47x.
Signed-off-by: Suzuki K. Poulose <suzuki@in.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Signed-off-by: Josh Boyer <jwboyer@gmail.com>
Diffstat (limited to 'arch/powerpc/include')
-rw-r--r-- | arch/powerpc/include/asm/page.h | 85 |
1 files changed, 82 insertions, 3 deletions
diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h index f149967ee6b..f072e974f8a 100644 --- a/arch/powerpc/include/asm/page.h +++ b/arch/powerpc/include/asm/page.h @@ -97,12 +97,26 @@ extern unsigned int HPAGE_SHIFT; extern phys_addr_t memstart_addr; extern phys_addr_t kernstart_addr; + +#ifdef CONFIG_RELOCATABLE_PPC32 +extern long long virt_phys_offset; #endif + +#endif /* __ASSEMBLY__ */ #define PHYSICAL_START kernstart_addr -#else + +#else /* !CONFIG_NONSTATIC_KERNEL */ #define PHYSICAL_START ASM_CONST(CONFIG_PHYSICAL_START) #endif +/* See Description below for VIRT_PHYS_OFFSET */ +#ifdef CONFIG_RELOCATABLE_PPC32 +#define VIRT_PHYS_OFFSET virt_phys_offset +#else +#define VIRT_PHYS_OFFSET (KERNELBASE - PHYSICAL_START) +#endif + + #ifdef CONFIG_PPC64 #define MEMORY_START 0UL #elif defined(CONFIG_NONSTATIC_KERNEL) @@ -125,12 +139,77 @@ extern phys_addr_t kernstart_addr; * determine MEMORY_START until then. However we can determine PHYSICAL_START * from information at hand (program counter, TLB lookup). * + * On BookE with RELOCATABLE (RELOCATABLE_PPC32) + * + * With RELOCATABLE_PPC32, we support loading the kernel at any physical + * address without any restriction on the page alignment. + * + * We find the runtime address of _stext and relocate ourselves based on + * the following calculation: + * + * virtual_base = ALIGN_DOWN(KERNELBASE,256M) + + * MODULO(_stext.run,256M) + * and create the following mapping: + * + * ALIGN_DOWN(_stext.run,256M) => ALIGN_DOWN(KERNELBASE,256M) + * + * When we process relocations, we cannot depend on the + * existing equation for the __va()/__pa() translations: + * + * __va(x) = (x) - PHYSICAL_START + KERNELBASE + * + * Where: + * PHYSICAL_START = kernstart_addr = Physical address of _stext + * KERNELBASE = Compiled virtual address of _stext. + * + * This formula holds true iff, kernel load address is TLB page aligned. + * + * In our case, we need to also account for the shift in the kernel Virtual + * address. + * + * E.g., + * + * Let the kernel be loaded at 64MB and KERNELBASE be 0xc0000000 (same as PAGE_OFFSET). + * In this case, we would be mapping 0 to 0xc0000000, and kernstart_addr = 64M + * + * Now __va(1MB) = (0x100000) - (0x4000000) + 0xc0000000 + * = 0xbc100000 , which is wrong. + * + * Rather, it should be : 0xc0000000 + 0x100000 = 0xc0100000 + * according to our mapping. + * + * Hence we use the following formula to get the translations right: + * + * __va(x) = (x) - [ PHYSICAL_START - Effective KERNELBASE ] + * + * Where : + * PHYSICAL_START = dynamic load address.(kernstart_addr variable) + * Effective KERNELBASE = virtual_base = + * = ALIGN_DOWN(KERNELBASE,256M) + + * MODULO(PHYSICAL_START,256M) + * + * To make the cost of __va() / __pa() more light weight, we introduce + * a new variable virt_phys_offset, which will hold : + * + * virt_phys_offset = Effective KERNELBASE - PHYSICAL_START + * = ALIGN_DOWN(KERNELBASE,256M) - + * ALIGN_DOWN(PHYSICALSTART,256M) + * + * Hence : + * + * __va(x) = x - PHYSICAL_START + Effective KERNELBASE + * = x + virt_phys_offset + * + * and + * __pa(x) = x + PHYSICAL_START - Effective KERNELBASE + * = x - virt_phys_offset + * * On non-Book-E PPC64 PAGE_OFFSET and MEMORY_START are constants so use * the other definitions for __va & __pa. */ #ifdef CONFIG_BOOKE -#define __va(x) ((void *)(unsigned long)((phys_addr_t)(x) - PHYSICAL_START + KERNELBASE)) -#define __pa(x) ((unsigned long)(x) + PHYSICAL_START - KERNELBASE) +#define __va(x) ((void *)(unsigned long)((phys_addr_t)(x) + VIRT_PHYS_OFFSET)) +#define __pa(x) ((unsigned long)(x) - VIRT_PHYS_OFFSET) #else #define __va(x) ((void *)(unsigned long)((phys_addr_t)(x) + PAGE_OFFSET - MEMORY_START)) #define __pa(x) ((unsigned long)(x) - PAGE_OFFSET + MEMORY_START) |