fe11dc3f96
Update the TLB asm to make proper use of _PAGE_DIRY and _PAGE_ACCESSED.
Get rid of _PAGE_HWWRITE too.
Pros:
- I/D TLB Miss never needs to write to the linux pte.
- _PAGE_ACCESSED is only set on TLB Error fixing accounting
- _PAGE_DIRTY is mapped to 0x100, the changed bit, and is set directly
when a page has been made dirty.
- Proper RO/RW mapping of user space.
- Free up 2 SW TLB bits in the linux pte(add back _PAGE_WRITETHRU ?)
- kernel RO/user NA support.
Cons:
- A few more instructions in the TLB Miss routines.
Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
67 lines
2.9 KiB
C
67 lines
2.9 KiB
C
#ifndef _ASM_POWERPC_PTE_8xx_H
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#define _ASM_POWERPC_PTE_8xx_H
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#ifdef __KERNEL__
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/*
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* The PowerPC MPC8xx uses a TLB with hardware assisted, software tablewalk.
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* We also use the two level tables, but we can put the real bits in them
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* needed for the TLB and tablewalk. These definitions require Mx_CTR.PPM = 0,
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* Mx_CTR.PPCS = 0, and MD_CTR.TWAM = 1. The level 2 descriptor has
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* additional page protection (when Mx_CTR.PPCS = 1) that allows TLB hit
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* based upon user/super access. The TLB does not have accessed nor write
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* protect. We assume that if the TLB get loaded with an entry it is
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* accessed, and overload the changed bit for write protect. We use
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* two bits in the software pte that are supposed to be set to zero in
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* the TLB entry (24 and 25) for these indicators. Although the level 1
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* descriptor contains the guarded and writethrough/copyback bits, we can
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* set these at the page level since they get copied from the Mx_TWC
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* register when the TLB entry is loaded. We will use bit 27 for guard, since
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* that is where it exists in the MD_TWC, and bit 26 for writethrough.
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* These will get masked from the level 2 descriptor at TLB load time, and
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* copied to the MD_TWC before it gets loaded.
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* Large page sizes added. We currently support two sizes, 4K and 8M.
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* This also allows a TLB hander optimization because we can directly
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* load the PMD into MD_TWC. The 8M pages are only used for kernel
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* mapping of well known areas. The PMD (PGD) entries contain control
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* flags in addition to the address, so care must be taken that the
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* software no longer assumes these are only pointers.
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*/
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/* Definitions for 8xx embedded chips. */
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#define _PAGE_PRESENT 0x0001 /* Page is valid */
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#define _PAGE_FILE 0x0002 /* when !present: nonlinear file mapping */
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#define _PAGE_NO_CACHE 0x0002 /* I: cache inhibit */
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#define _PAGE_SHARED 0x0004 /* No ASID (context) compare */
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#define _PAGE_SPECIAL 0x0008 /* SW entry, forced to 0 by the TLB miss */
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#define _PAGE_DIRTY 0x0100 /* C: page changed */
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/* These 3 software bits must be masked out when the entry is loaded
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* into the TLB, 2 SW bits left.
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*/
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#define _PAGE_GUARDED 0x0010 /* software: guarded access */
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#define _PAGE_ACCESSED 0x0020 /* software: page referenced */
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/* Setting any bits in the nibble with the follow two controls will
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* require a TLB exception handler change. It is assumed unused bits
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* are always zero.
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*/
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#define _PAGE_RW 0x0400 /* lsb PP bits, inverted in HW */
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#define _PAGE_USER 0x0800 /* msb PP bits */
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#define _PMD_PRESENT 0x0001
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#define _PMD_BAD 0x0ff0
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#define _PMD_PAGE_MASK 0x000c
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#define _PMD_PAGE_8M 0x000c
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#define _PTE_NONE_MASK _PAGE_ACCESSED
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/* Until my rework is finished, 8xx still needs atomic PTE updates */
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#define PTE_ATOMIC_UPDATES 1
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/* We need to add _PAGE_SHARED to kernel pages */
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#define _PAGE_KERNEL_RO (_PAGE_SHARED)
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#define _PAGE_KERNEL_RW (_PAGE_DIRTY | _PAGE_RW | _PAGE_HWWRITE)
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#endif /* __KERNEL__ */
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#endif /* _ASM_POWERPC_PTE_8xx_H */
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