| /* $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> |
| |
| #if PAGE_SHIFT == 13 |
| #define SZ_BITS _PAGE_SZ8K |
| #elif PAGE_SHIFT == 16 |
| #define SZ_BITS _PAGE_SZ64K |
| #elif PAGE_SHIFT == 19 |
| #define SZ_BITS _PAGE_SZ512K |
| #elif PAGE_SHIFT == 22 |
| #define SZ_BITS _PAGE_SZ4MB |
| #endif |
| |
| #define VALID_SZ_BITS (_PAGE_VALID | SZ_BITS) |
| |
| #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 SZ_BITS |
| #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 |
| |
