/* $Id: dtlb_base.S,v 1.7 2000/03/26 09:13:48 davem Exp $ * dtlb_base.S: Front 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) */ #define TAG_CONTEXT_BITS 0x3ff #define VPTE_SHIFT (PAGE_SHIFT - 3) #define KERN_HIGHBITS ((_PAGE_VALID | _PAGE_SZ4MB) ^ 0xfffff80000000000) #define KERN_LOWBITS (_PAGE_CP | _PAGE_CV | _PAGE_P | _PAGE_W) #define KERN_LOWBITS_IO (_PAGE_E | _PAGE_P | _PAGE_W) #define KERN_IOBITS (KERN_LOWBITS ^ KERN_LOWBITS_IO) /* %g1 TLB_SFSR (%g1 + %g1 == TLB_TAG_ACCESS) * %g2 (KERN_HIGHBITS | KERN_LOWBITS) * %g3 VPTE base (0xfffffffe00000000) Spitfire/Blackbird (44-bit VA space) * (0xffe0000000000000) Cheetah (64-bit VA space) * %g7 __pa(current->mm->pgd) * * The VPTE base value is completely magic, but note that * nothing else in the kernel other than these TLB miss * handlers know anything about the VPTE mechanism or * how it works. Consider the 44-bit VADDR Ultra-I/II * case as an example: * * VA[0 : (1<<43)] produce VPTE index [%g3 : 0] * VA[0 : -(1<<43)] produce VPTE index [%g3-(1<<(43-PAGE_SHIFT+3)) : %g3] * * For Cheetah's 64-bit VADDR space this is: * * VA[0 : (1<<63)] produce VPTE index [%g3 : 0] * VA[0 : -(1<<63)] produce VPTE index [%g3-(1<<(63-PAGE_SHIFT+3)) : %g3] * * If you're paying attention you'll notice that this means half of * the VPTE table is above %g3 and half is below, low VA addresses * map progressively upwards from %g3, and high VA addresses map * progressively downwards from %g3. This trick was needed to make * the same 8 instruction handler work both for Spitfire/Blackbird's * peculiar VA space hole configuration and the full 64-bit VA space * one of Cheetah at the same time. */ /* Ways we can get here: * * 1) Nucleus loads and stores to/from PA-->VA direct mappings. * 2) Nucleus loads and stores to/from vmalloc() areas. * 3) User loads and stores. * 4) User space accesses by nucleus at tl0 */ /* DTLB ** ICACHE line 1: Quick user TLB misses */ ldxa [%g1 + %g1] ASI_DMMU, %g4 ! Get TAG_ACCESS andcc %g4, TAG_CONTEXT_BITS, %g0 ! From Nucleus? be,pn %xcc, 3f ! Yep, special processing srax %g4, VPTE_SHIFT, %g6 ! Create VPTE offset ldxa [%g3 + %g6] ASI_S, %g5 ! Load VPTE 1: brlz,pt %g5, 9f ! Valid, load into TLB and %g5, (_PAGE_PRESENT|_PAGE_READ), %g4 ! Mask readable bits ba,a,pt %xcc, 4f ! Invalid, branch out /* DTLB ** ICACHE line 2: Quick kernel TLB misses */ 3: brlz,pt %g4, 9f ! Kernel virtual map? xor %g2, %g4, %g5 ! Finish bit twiddles ldxa [%g3 + %g6] ASI_N, %g5 ! Yep, load k-vpte ba,pt %xcc, 1b ! Continue tlb reload nop 9: stxa %g5, [%g0] ASI_DTLB_DATA_IN ! Reload TLB retry ! Trap return nop /* DTLB ** ICACHE line 3: winfixups+real_faults */ 4: cmp %g4, (_PAGE_PRESENT|_PAGE_READ) ! Readable page? be,pn %xcc, 5f ! Yep, refbit update sllx %g1, 60, %g4 ! Get valid bit rdpr %pstate, %g5 ! Move into alternate globals wrpr %g5, PSTATE_AG|PSTATE_MG, %pstate rdpr %tl, %g4 ! See where we came from. cmp %g4, 1 ! Is etrap/rtrap window fault? mov TLB_TAG_ACCESS, %g4 ! Prepare for fault processing /* DTLB ** ICACHE line 4: padding */ ldxa [%g4] ASI_DMMU, %g5 ! Load faulting VA page be,pt %xcc, sparc64_realfault_common ! Jump to normal fault handling mov FAULT_CODE_DTLB, %g4 ! It was read from DTLB ba,a,pt %xcc, winfix_trampoline ! Call window fixup code 5: or %g5, _PAGE_ACCESSED, %g5 ! Indicate reference or %g5, %g4, %g5 ! Set valid stxa %g5, [%g3 + %g6] ASI_S ! Update PTE table (cant trap) ba,a,pt %xcc, 9b ! Complete tlb miss #undef TAG_CONTEXT_BITS #undef VPTE_SHIFT #undef KERN_HIGHBITS #undef KERN_LOWBITS #undef KERN_LOWBITS_IO #undef KERN_IOBITS