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/* $Id: dtlb_base.S,v 1.17 2001/10/11 22:33:52 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)
*/
#include <asm/pgtable.h>
#include <asm/mmu.h>
/* %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
* few places in the kernel other than these TLB miss
* handlers know anything about the VPTE mechanism or
* how it works (see VPTE_SIZE, TASK_SIZE and PTRS_PER_PGD).
* 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 upwards towards %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
*/
#if PAGE_SHIFT == 13
/*
* To compute vpte offset, we need to do ((addr >> 13) << 3),
* which can be optimized to (addr >> 10) if bits 10/11/12 can
* be guaranteed to be 0 ... mmu_context.h does guarantee this
* by only using 10 bits in the hwcontext value.
*/
#define CREATE_VPTE_OFFSET1(r1, r2)
#define CREATE_VPTE_OFFSET2(r1, r2) \
srax r1, 10, r2
#define CREATE_VPTE_NOP nop
#else
#define CREATE_VPTE_OFFSET1(r1, r2) \
srax r1, PAGE_SHIFT, r2
#define CREATE_VPTE_OFFSET2(r1, r2) \
sllx r2, 3, r2
#define CREATE_VPTE_NOP
#endif
/* 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?
from_tl1_trap:
rdpr %tl, %g5 ! For TL==3 test
CREATE_VPTE_OFFSET1(%g4, %g6) ! Create VPTE offset
be,pn %xcc, kvmap ! Yep, special processing
CREATE_VPTE_OFFSET2(%g4, %g6) ! Create VPTE offset
cmp %g5, 4 ! Last trap level?
be,pn %xcc, longpath ! Yep, cannot risk VPTE miss
nop ! delay slot
/* DTLB ** ICACHE line 2: User finish + quick kernel TLB misses */
ldxa [%g3 + %g6] ASI_S, %g5 ! Load VPTE
1: brgez,pn %g5, longpath ! Invalid, branch out
nop ! Delay-slot
9: stxa %g5, [%g0] ASI_DTLB_DATA_IN ! Reload TLB
retry ! Trap return
nop
nop
nop
/* DTLB ** ICACHE line 3: winfixups+real_faults */
longpath:
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
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
/* DTLB ** ICACHE line 4: Unused... */
ba,a,pt %xcc, winfix_trampoline ! Call window fixup code
nop
nop
nop
nop
nop
nop
CREATE_VPTE_NOP
#undef CREATE_VPTE_OFFSET1
#undef CREATE_VPTE_OFFSET2
#undef CREATE_VPTE_NOP
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