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481535c5b4
fast_second_level_miss handler for the TLBTEMP area has an assumption that page table directory entry for the TLBTEMP address range is 0. For it to be true the TLBTEMP area must be aligned to 4MB boundary and not share its 4MB region with anything that may use a page table. This is not true currently: TLBTEMP shares space with vmalloc space which results in the following kinds of runtime errors when fast_second_level_miss loads page table directory entry for the vmalloc space instead of fixing up the TLBTEMP area: Unable to handle kernel paging request at virtual address c7ff0e00 pc = d0009275, ra = 90009478 Oops: sig: 9 [#1] PREEMPT CPU: 1 PID: 61 Comm: kworker/u9:2 Not tainted 5.10.0-rc3-next-20201110-00007-g1fe4962fa983-dirty #58 Workqueue: xprtiod xs_stream_data_receive_workfn a00: 90009478 d11e1dc0 c7ff0e00 00000020 c7ff0000 00000001 7f8b8107 00000000 a08: 900c5992d11e1d90d0cc88b8 5506e97c 00000000 5506e97c d06c8074d11e1d90pc: d0009275, ps: 00060310, depc: 00000014, excvaddr: c7ff0e00 lbeg: d0009275, lend: d0009287 lcount: 00000003, sar: 00000010 Call Trace: xs_stream_data_receive_workfn+0x43c/0x770 process_one_work+0x1a1/0x324 worker_thread+0x1cc/0x3c0 kthread+0x10d/0x124 ret_from_kernel_thread+0xc/0x18 Cc: stable@vger.kernel.org Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
199 lines
8.6 KiB
ReStructuredText
199 lines
8.6 KiB
ReStructuredText
=============================
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MMUv3 initialization sequence
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=============================
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The code in the initialize_mmu macro sets up MMUv3 memory mapping
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identically to MMUv2 fixed memory mapping. Depending on
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CONFIG_INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX symbol this code is
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located in addresses it was linked for (symbol undefined), or not
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(symbol defined), so it needs to be position-independent.
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The code has the following assumptions:
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- This code fragment is run only on an MMU v3.
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- TLBs are in their reset state.
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- ITLBCFG and DTLBCFG are zero (reset state).
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- RASID is 0x04030201 (reset state).
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- PS.RING is zero (reset state).
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- LITBASE is zero (reset state, PC-relative literals); required to be PIC.
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TLB setup proceeds along the following steps.
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Legend:
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- VA = virtual address (two upper nibbles of it);
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- PA = physical address (two upper nibbles of it);
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- pc = physical range that contains this code;
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After step 2, we jump to virtual address in the range 0x40000000..0x5fffffff
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or 0x00000000..0x1fffffff, depending on whether the kernel was loaded below
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0x40000000 or above. That address corresponds to next instruction to execute
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in this code. After step 4, we jump to intended (linked) address of this code.
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The scheme below assumes that the kernel is loaded below 0x40000000.
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====== ===== ===== ===== ===== ====== ===== =====
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- Step0 Step1 Step2 Step3 Step4 Step5
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VA PA PA PA PA VA PA PA
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====== ===== ===== ===== ===== ====== ===== =====
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E0..FF -> E0 -> E0 -> E0 F0..FF -> F0 -> F0
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C0..DF -> C0 -> C0 -> C0 E0..EF -> F0 -> F0
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A0..BF -> A0 -> A0 -> A0 D8..DF -> 00 -> 00
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80..9F -> 80 -> 80 -> 80 D0..D7 -> 00 -> 00
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60..7F -> 60 -> 60 -> 60
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40..5F -> 40 -> pc -> pc 40..5F -> pc
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20..3F -> 20 -> 20 -> 20
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00..1F -> 00 -> 00 -> 00
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====== ===== ===== ===== ===== ====== ===== =====
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The default location of IO peripherals is above 0xf0000000. This may be changed
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using a "ranges" property in a device tree simple-bus node. See the Devicetree
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Specification, section 4.5 for details on the syntax and semantics of
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simple-bus nodes. The following limitations apply:
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1. Only top level simple-bus nodes are considered
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2. Only one (first) simple-bus node is considered
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3. Empty "ranges" properties are not supported
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4. Only the first triplet in the "ranges" property is considered
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5. The parent-bus-address value is rounded down to the nearest 256MB boundary
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6. The IO area covers the entire 256MB segment of parent-bus-address; the
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"ranges" triplet length field is ignored
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MMUv3 address space layouts.
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============================
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Default MMUv2-compatible layout::
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Symbol VADDR Size
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+------------------+
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| Userspace | 0x00000000 TASK_SIZE
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+------------------+ 0x40000000
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+------------------+
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| Page table | XCHAL_PAGE_TABLE_VADDR 0x80000000 XCHAL_PAGE_TABLE_SIZE
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+------------------+
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| KASAN shadow map | KASAN_SHADOW_START 0x80400000 KASAN_SHADOW_SIZE
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+------------------+ 0x8e400000
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+------------------+
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| VMALLOC area | VMALLOC_START 0xc0000000 128MB - 64KB
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+------------------+ VMALLOC_END
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+------------------+
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| Cache aliasing | TLBTEMP_BASE_1 0xc8000000 DCACHE_WAY_SIZE
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| remap area 1 |
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+------------------+
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| Cache aliasing | TLBTEMP_BASE_2 DCACHE_WAY_SIZE
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| remap area 2 |
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+------------------+
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+------------------+
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| KMAP area | PKMAP_BASE PTRS_PER_PTE *
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| | DCACHE_N_COLORS *
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| | PAGE_SIZE
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| | (4MB * DCACHE_N_COLORS)
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+------------------+
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| Atomic KMAP area | FIXADDR_START KM_TYPE_NR *
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| | NR_CPUS *
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| | DCACHE_N_COLORS *
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| | PAGE_SIZE
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+------------------+ FIXADDR_TOP 0xcffff000
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+------------------+
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| Cached KSEG | XCHAL_KSEG_CACHED_VADDR 0xd0000000 128MB
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+------------------+
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| Uncached KSEG | XCHAL_KSEG_BYPASS_VADDR 0xd8000000 128MB
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+------------------+
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| Cached KIO | XCHAL_KIO_CACHED_VADDR 0xe0000000 256MB
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+------------------+
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| Uncached KIO | XCHAL_KIO_BYPASS_VADDR 0xf0000000 256MB
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+------------------+
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256MB cached + 256MB uncached layout::
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Symbol VADDR Size
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+------------------+
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| Userspace | 0x00000000 TASK_SIZE
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+------------------+ 0x40000000
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+------------------+
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| Page table | XCHAL_PAGE_TABLE_VADDR 0x80000000 XCHAL_PAGE_TABLE_SIZE
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+------------------+
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| KASAN shadow map | KASAN_SHADOW_START 0x80400000 KASAN_SHADOW_SIZE
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+------------------+ 0x8e400000
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+------------------+
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| VMALLOC area | VMALLOC_START 0xa0000000 128MB - 64KB
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+------------------+ VMALLOC_END
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+------------------+
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| Cache aliasing | TLBTEMP_BASE_1 0xa8000000 DCACHE_WAY_SIZE
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| remap area 1 |
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+------------------+
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| Cache aliasing | TLBTEMP_BASE_2 DCACHE_WAY_SIZE
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| remap area 2 |
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+------------------+
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+------------------+
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| KMAP area | PKMAP_BASE PTRS_PER_PTE *
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| | DCACHE_N_COLORS *
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| | PAGE_SIZE
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| | (4MB * DCACHE_N_COLORS)
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+------------------+
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| Atomic KMAP area | FIXADDR_START KM_TYPE_NR *
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| | NR_CPUS *
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| | DCACHE_N_COLORS *
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| | PAGE_SIZE
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+------------------+ FIXADDR_TOP 0xaffff000
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+------------------+
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| Cached KSEG | XCHAL_KSEG_CACHED_VADDR 0xb0000000 256MB
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+------------------+
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| Uncached KSEG | XCHAL_KSEG_BYPASS_VADDR 0xc0000000 256MB
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+------------------+
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+------------------+
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| Cached KIO | XCHAL_KIO_CACHED_VADDR 0xe0000000 256MB
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+------------------+
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| Uncached KIO | XCHAL_KIO_BYPASS_VADDR 0xf0000000 256MB
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+------------------+
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512MB cached + 512MB uncached layout::
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Symbol VADDR Size
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+------------------+
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| Userspace | 0x00000000 TASK_SIZE
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+------------------+ 0x40000000
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+------------------+
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| Page table | XCHAL_PAGE_TABLE_VADDR 0x80000000 XCHAL_PAGE_TABLE_SIZE
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+------------------+
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| KASAN shadow map | KASAN_SHADOW_START 0x80400000 KASAN_SHADOW_SIZE
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+------------------+ 0x8e400000
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+------------------+
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| VMALLOC area | VMALLOC_START 0x90000000 128MB - 64KB
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+------------------+ VMALLOC_END
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+------------------+
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| Cache aliasing | TLBTEMP_BASE_1 0x98000000 DCACHE_WAY_SIZE
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| remap area 1 |
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+------------------+
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| Cache aliasing | TLBTEMP_BASE_2 DCACHE_WAY_SIZE
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| remap area 2 |
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+------------------+
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+------------------+
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| KMAP area | PKMAP_BASE PTRS_PER_PTE *
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| | DCACHE_N_COLORS *
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| | PAGE_SIZE
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| | (4MB * DCACHE_N_COLORS)
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+------------------+
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| Atomic KMAP area | FIXADDR_START KM_TYPE_NR *
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| | NR_CPUS *
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| | DCACHE_N_COLORS *
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| | PAGE_SIZE
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+------------------+ FIXADDR_TOP 0x9ffff000
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+------------------+
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| Cached KSEG | XCHAL_KSEG_CACHED_VADDR 0xa0000000 512MB
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+------------------+
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| Uncached KSEG | XCHAL_KSEG_BYPASS_VADDR 0xc0000000 512MB
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+------------------+
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| Cached KIO | XCHAL_KIO_CACHED_VADDR 0xe0000000 256MB
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+------------------+
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| Uncached KIO | XCHAL_KIO_BYPASS_VADDR 0xf0000000 256MB
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+------------------+
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