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/* $Id: dtlb_backend.S,v 1.16 2001/10/09 04:02:11 davem Exp $
* dtlb_backend.S: Back end to DTLB miss replacement strategy.
* This is included directly into the trap table.
*
* Copyright (C) 1996,1998 David S. Miller (davem@redhat.com)
* Copyright (C) 1997,1998 Jakub Jelinek (jj@ultra.linux.cz)
*/
#include <asm/pgtable.h>
#include <asm/mmu.h>
#define VALID_SZ_BITS (_PAGE_VALID | _PAGE_SZBITS)
#define VPTE_BITS (_PAGE_CP | _PAGE_CV | _PAGE_P )
#define VPTE_SHIFT (PAGE_SHIFT - 3)
/* Ways we can get here:
*
* 1) Nucleus loads and stores to/from PA-->VA direct mappings at tl>1.
* 2) Nucleus loads and stores to/from user/kernel window save areas.
* 3) VPTE misses from dtlb_base and itlb_base.
*
* We need to extract out the PMD and PGDIR indexes from the
* linear virtual page table access address. The PTE index
* is at the bottom, but we are not concerned with it. Bits
* 0 to 2 are clear since each PTE is 8 bytes in size. Each
* PMD and PGDIR entry are 4 bytes in size. Thus, this
* address looks something like:
*
* |---------------------------------------------------------------|
* | ... | PGDIR index | PMD index | PTE index | |
* |---------------------------------------------------------------|
* 63 F E D C B A 3 2 0 <- bit nr
*
* The variable bits above are defined as:
* A --> 3 + (PAGE_SHIFT - log2(8))
* --> 3 + (PAGE_SHIFT - 3) - 1
* (ie. this is "bit 3" + PAGE_SIZE - size of PTE entry in bits - 1)
* B --> A + 1
* C --> B + (PAGE_SHIFT - log2(4))
* --> B + (PAGE_SHIFT - 2) - 1
* (ie. this is "bit B" + PAGE_SIZE - size of PMD entry in bits - 1)
* D --> C + 1
* E --> D + (PAGE_SHIFT - log2(4))
* --> D + (PAGE_SHIFT - 2) - 1
* (ie. this is "bit D" + PAGE_SIZE - size of PGDIR entry in bits - 1)
* F --> E + 1
*
* (Note how "B" always evalutes to PAGE_SHIFT, all the other constants
* cancel out.)
*
* For 8K PAGE_SIZE (thus, PAGE_SHIFT of 13) the bit numbers are:
* A --> 12
* B --> 13
* C --> 23
* D --> 24
* E --> 34
* F --> 35
*
* For 64K PAGE_SIZE (thus, PAGE_SHIFT of 16) the bit numbers are:
* A --> 15
* B --> 16
* C --> 29
* D --> 30
* E --> 43
* F --> 44
*
* Because bits both above and below each PGDIR and PMD index need to
* be masked out, and the index can be as long as 14 bits (when using a
* 64K PAGE_SIZE, and thus a PAGE_SHIFT of 16), we need 3 instructions
* to extract each index out.
*
* Shifts do not pair very well on UltraSPARC-I, II, IIi, and IIe, so
* we try to avoid using them for the entire operation. We could setup
* a mask anywhere from bit 31 down to bit 10 using the sethi instruction.
*
* We need a mask covering bits B --> C and one covering D --> E.
* For 8K PAGE_SIZE these masks are 0x00ffe000 and 0x7ff000000.
* For 64K PAGE_SIZE these masks are 0x3fff0000 and 0xfffc0000000.
* The second in each set cannot be loaded with a single sethi
* instruction, because the upper bits are past bit 32. We would
* need to use a sethi + a shift.
*
* For the time being, we use 2 shifts and a simple "and" mask.
* We shift left to clear the bits above the index, we shift down
* to clear the bits below the index (sans the log2(4 or 8) bits)
* and a mask to clear the log2(4 or 8) bits. We need therefore
* define 4 shift counts, all of which are relative to PAGE_SHIFT.
*
* Although unsupportable for other reasons, this does mean that
* 512K and 4MB page sizes would be generaally supported by the
* kernel. (ELF binaries would break with > 64K PAGE_SIZE since
* the sections are only aligned that strongly).
*
* The operations performed for extraction are thus:
*
* ((X << FOO_SHIFT_LEFT) >> FOO_SHIFT_RIGHT) & ~0x3
*
*/
#define A (3 + (PAGE_SHIFT - 3) - 1)
#define B (A + 1)
#define C (B + (PAGE_SHIFT - 2) - 1)
#define D (C + 1)
#define E (D + (PAGE_SHIFT - 2) - 1)
#define F (E + 1)
#define PMD_SHIFT_LEFT (64 - D)
#define PMD_SHIFT_RIGHT (64 - (D - B) - 2)
#define PGDIR_SHIFT_LEFT (64 - F)
#define PGDIR_SHIFT_RIGHT (64 - (F - D) - 2)
#define LOW_MASK_BITS 0x3
/* TLB1 ** ICACHE line 1: tl1 DTLB and quick VPTE miss */
ldxa [%g1 + %g1] ASI_DMMU, %g4 ! Get TAG_ACCESS
add %g3, %g3, %g5 ! Compute VPTE base
cmp %g4, %g5 ! VPTE miss?
bgeu,pt %xcc, 1f ! Continue here
andcc %g4, TAG_CONTEXT_BITS, %g5 ! tl0 miss Nucleus test
ba,a,pt %xcc, from_tl1_trap ! Fall to tl0 miss
1: sllx %g6, VPTE_SHIFT, %g4 ! Position TAG_ACCESS
or %g4, %g5, %g4 ! Prepare TAG_ACCESS
/* TLB1 ** ICACHE line 2: Quick VPTE miss */
mov TSB_REG, %g1 ! Grab TSB reg
ldxa [%g1] ASI_DMMU, %g5 ! Doing PGD caching?
sllx %g6, PMD_SHIFT_LEFT, %g1 ! Position PMD offset
be,pn %xcc, sparc64_vpte_nucleus ! Is it from Nucleus?
srlx %g1, PMD_SHIFT_RIGHT, %g1 ! Mask PMD offset bits
brnz,pt %g5, sparc64_vpte_continue ! Yep, go like smoke
andn %g1, LOW_MASK_BITS, %g1 ! Final PMD mask
sllx %g6, PGDIR_SHIFT_LEFT, %g5 ! Position PGD offset
/* TLB1 ** ICACHE line 3: Quick VPTE miss */
srlx %g5, PGDIR_SHIFT_RIGHT, %g5 ! Mask PGD offset bits
andn %g5, LOW_MASK_BITS, %g5 ! Final PGD mask
lduwa [%g7 + %g5] ASI_PHYS_USE_EC, %g5! Load PGD
brz,pn %g5, vpte_noent ! Valid?
sparc64_kpte_continue:
sllx %g5, 11, %g5 ! Shift into place
sparc64_vpte_continue:
lduwa [%g5 + %g1] ASI_PHYS_USE_EC, %g5! Load PMD
sllx %g5, 11, %g5 ! Shift into place
brz,pn %g5, vpte_noent ! Valid?
/* TLB1 ** ICACHE line 4: Quick VPTE miss */
mov (VALID_SZ_BITS >> 61), %g1 ! upper vpte into %g1
sllx %g1, 61, %g1 ! finish calc
or %g5, VPTE_BITS, %g5 ! Prepare VPTE data
or %g5, %g1, %g5 ! ...
mov TLB_SFSR, %g1 ! Restore %g1 value
stxa %g5, [%g0] ASI_DTLB_DATA_IN ! Load VPTE into TLB
stxa %g4, [%g1 + %g1] ASI_DMMU ! Restore previous TAG_ACCESS
retry ! Load PTE once again
#undef VALID_SZ_BITS
#undef VPTE_SHIFT
#undef VPTE_BITS
#undef A
#undef B
#undef C
#undef D
#undef E
#undef F
#undef PMD_SHIFT_LEFT
#undef PMD_SHIFT_RIGHT
#undef PGDIR_SHIFT_LEFT
#undef PGDIR_SHIFT_RIGHT
#undef LOW_MASK_BITS
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