The 'addr' field in the CPUIOTLBEntry struct has a rather non-obvious use; add a comment documenting it (reverse-engineered from what the code that sets it is doing). Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Message-id: 20180611125633.32755-2-peter.maydell@linaro.org
166 lines
6.2 KiB
C
166 lines
6.2 KiB
C
/*
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* common defines for all CPUs
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*
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* Copyright (c) 2003 Fabrice Bellard
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef CPU_DEFS_H
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#define CPU_DEFS_H
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#ifndef NEED_CPU_H
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#error cpu.h included from common code
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#endif
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#include "qemu/host-utils.h"
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#include "qemu/queue.h"
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#ifdef CONFIG_TCG
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#include "tcg-target.h"
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#endif
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#ifndef CONFIG_USER_ONLY
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#include "exec/hwaddr.h"
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#endif
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#include "exec/memattrs.h"
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#ifndef TARGET_LONG_BITS
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#error TARGET_LONG_BITS must be defined before including this header
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#endif
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#define TARGET_LONG_SIZE (TARGET_LONG_BITS / 8)
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/* target_ulong is the type of a virtual address */
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#if TARGET_LONG_SIZE == 4
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typedef int32_t target_long;
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typedef uint32_t target_ulong;
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#define TARGET_FMT_lx "%08x"
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#define TARGET_FMT_ld "%d"
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#define TARGET_FMT_lu "%u"
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#elif TARGET_LONG_SIZE == 8
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typedef int64_t target_long;
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typedef uint64_t target_ulong;
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#define TARGET_FMT_lx "%016" PRIx64
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#define TARGET_FMT_ld "%" PRId64
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#define TARGET_FMT_lu "%" PRIu64
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#else
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#error TARGET_LONG_SIZE undefined
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#endif
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#if !defined(CONFIG_USER_ONLY) && defined(CONFIG_TCG)
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/* use a fully associative victim tlb of 8 entries */
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#define CPU_VTLB_SIZE 8
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#if HOST_LONG_BITS == 32 && TARGET_LONG_BITS == 32
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#define CPU_TLB_ENTRY_BITS 4
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#else
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#define CPU_TLB_ENTRY_BITS 5
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#endif
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/* TCG_TARGET_TLB_DISPLACEMENT_BITS is used in CPU_TLB_BITS to ensure that
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* the TLB is not unnecessarily small, but still small enough for the
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* TLB lookup instruction sequence used by the TCG target.
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*
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* TCG will have to generate an operand as large as the distance between
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* env and the tlb_table[NB_MMU_MODES - 1][0].addend. For simplicity,
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* the TCG targets just round everything up to the next power of two, and
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* count bits. This works because: 1) the size of each TLB is a largish
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* power of two, 2) and because the limit of the displacement is really close
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* to a power of two, 3) the offset of tlb_table[0][0] inside env is smaller
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* than the size of a TLB.
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*
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* For example, the maximum displacement 0xFFF0 on PPC and MIPS, but TCG
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* just says "the displacement is 16 bits". TCG_TARGET_TLB_DISPLACEMENT_BITS
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* then ensures that tlb_table at least 0x8000 bytes large ("not unnecessarily
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* small": 2^15). The operand then will come up smaller than 0xFFF0 without
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* any particular care, because the TLB for a single MMU mode is larger than
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* 0x10000-0xFFF0=16 bytes. In the end, the maximum value of the operand
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* could be something like 0xC000 (the offset of the last TLB table) plus
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* 0x18 (the offset of the addend field in each TLB entry) plus the offset
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* of tlb_table inside env (which is non-trivial but not huge).
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*/
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#define CPU_TLB_BITS \
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MIN(8, \
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TCG_TARGET_TLB_DISPLACEMENT_BITS - CPU_TLB_ENTRY_BITS - \
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(NB_MMU_MODES <= 1 ? 0 : \
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NB_MMU_MODES <= 2 ? 1 : \
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NB_MMU_MODES <= 4 ? 2 : \
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NB_MMU_MODES <= 8 ? 3 : 4))
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#define CPU_TLB_SIZE (1 << CPU_TLB_BITS)
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typedef struct CPUTLBEntry {
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/* bit TARGET_LONG_BITS to TARGET_PAGE_BITS : virtual address
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bit TARGET_PAGE_BITS-1..4 : Nonzero for accesses that should not
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go directly to ram.
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bit 3 : indicates that the entry is invalid
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bit 2..0 : zero
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*/
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union {
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struct {
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target_ulong addr_read;
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target_ulong addr_write;
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target_ulong addr_code;
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/* Addend to virtual address to get host address. IO accesses
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use the corresponding iotlb value. */
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uintptr_t addend;
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};
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/* padding to get a power of two size */
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uint8_t dummy[1 << CPU_TLB_ENTRY_BITS];
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};
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} CPUTLBEntry;
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QEMU_BUILD_BUG_ON(sizeof(CPUTLBEntry) != (1 << CPU_TLB_ENTRY_BITS));
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/* The IOTLB is not accessed directly inline by generated TCG code,
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* so the CPUIOTLBEntry layout is not as critical as that of the
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* CPUTLBEntry. (This is also why we don't want to combine the two
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* structs into one.)
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*/
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typedef struct CPUIOTLBEntry {
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/*
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* @addr contains:
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* - in the lower TARGET_PAGE_BITS, a physical section number
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* - with the lower TARGET_PAGE_BITS masked off, an offset which
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* must be added to the virtual address to obtain:
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* + the ram_addr_t of the target RAM (if the physical section
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* number is PHYS_SECTION_NOTDIRTY or PHYS_SECTION_ROM)
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* + the offset within the target MemoryRegion (otherwise)
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*/
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hwaddr addr;
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MemTxAttrs attrs;
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} CPUIOTLBEntry;
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#define CPU_COMMON_TLB \
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/* The meaning of the MMU modes is defined in the target code. */ \
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CPUTLBEntry tlb_table[NB_MMU_MODES][CPU_TLB_SIZE]; \
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CPUTLBEntry tlb_v_table[NB_MMU_MODES][CPU_VTLB_SIZE]; \
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CPUIOTLBEntry iotlb[NB_MMU_MODES][CPU_TLB_SIZE]; \
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CPUIOTLBEntry iotlb_v[NB_MMU_MODES][CPU_VTLB_SIZE]; \
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size_t tlb_flush_count; \
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target_ulong tlb_flush_addr; \
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target_ulong tlb_flush_mask; \
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target_ulong vtlb_index; \
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#else
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#define CPU_COMMON_TLB
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#endif
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#define CPU_COMMON \
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/* soft mmu support */ \
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CPU_COMMON_TLB \
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#endif
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