summaryrefslogtreecommitdiffstats
path: root/src/common/host_memory.cpp
blob: ba22595e06a93eebfe6330110880a3163989a928 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
// SPDX-FileCopyrightText: Copyright 2021 yuzu Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later

#ifdef _WIN32

#include <iterator>
#include <unordered_map>
#include <boost/icl/separate_interval_set.hpp>
#include <windows.h>
#include "common/dynamic_library.h"

#elif defined(__linux__) || defined(__FreeBSD__) // ^^^ Windows ^^^ vvv Linux vvv

#ifdef ANDROID
#include <android/sharedmem.h>
#endif

#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <boost/icl/interval_set.hpp>
#include <fcntl.h>
#include <sys/mman.h>
#include <unistd.h>
#include "common/scope_exit.h"

#endif // ^^^ Linux ^^^

#include <mutex>

#include "common/alignment.h"
#include "common/assert.h"
#include "common/host_memory.h"
#include "common/logging/log.h"

namespace Common {

constexpr size_t PageAlignment = 0x1000;
constexpr size_t HugePageSize = 0x200000;

#ifdef _WIN32

// Manually imported for MinGW compatibility
#ifndef MEM_RESERVE_PLACEHOLDER
#define MEM_RESERVE_PLACEHOLDER 0x00040000
#endif
#ifndef MEM_REPLACE_PLACEHOLDER
#define MEM_REPLACE_PLACEHOLDER 0x00004000
#endif
#ifndef MEM_COALESCE_PLACEHOLDERS
#define MEM_COALESCE_PLACEHOLDERS 0x00000001
#endif
#ifndef MEM_PRESERVE_PLACEHOLDER
#define MEM_PRESERVE_PLACEHOLDER 0x00000002
#endif

using PFN_CreateFileMapping2 = _Ret_maybenull_ HANDLE(WINAPI*)(
    _In_ HANDLE File, _In_opt_ SECURITY_ATTRIBUTES* SecurityAttributes, _In_ ULONG DesiredAccess,
    _In_ ULONG PageProtection, _In_ ULONG AllocationAttributes, _In_ ULONG64 MaximumSize,
    _In_opt_ PCWSTR Name,
    _Inout_updates_opt_(ParameterCount) MEM_EXTENDED_PARAMETER* ExtendedParameters,
    _In_ ULONG ParameterCount);

using PFN_VirtualAlloc2 = _Ret_maybenull_ PVOID(WINAPI*)(
    _In_opt_ HANDLE Process, _In_opt_ PVOID BaseAddress, _In_ SIZE_T Size,
    _In_ ULONG AllocationType, _In_ ULONG PageProtection,
    _Inout_updates_opt_(ParameterCount) MEM_EXTENDED_PARAMETER* ExtendedParameters,
    _In_ ULONG ParameterCount);

using PFN_MapViewOfFile3 = _Ret_maybenull_ PVOID(WINAPI*)(
    _In_ HANDLE FileMapping, _In_opt_ HANDLE Process, _In_opt_ PVOID BaseAddress,
    _In_ ULONG64 Offset, _In_ SIZE_T ViewSize, _In_ ULONG AllocationType, _In_ ULONG PageProtection,
    _Inout_updates_opt_(ParameterCount) MEM_EXTENDED_PARAMETER* ExtendedParameters,
    _In_ ULONG ParameterCount);

using PFN_UnmapViewOfFile2 = BOOL(WINAPI*)(_In_ HANDLE Process, _In_ PVOID BaseAddress,
                                           _In_ ULONG UnmapFlags);

template <typename T>
static void GetFuncAddress(Common::DynamicLibrary& dll, const char* name, T& pfn) {
    if (!dll.GetSymbol(name, &pfn)) {
        LOG_CRITICAL(HW_Memory, "Failed to load {}", name);
        throw std::bad_alloc{};
    }
}

class HostMemory::Impl {
public:
    explicit Impl(size_t backing_size_, size_t virtual_size_)
        : backing_size{backing_size_}, virtual_size{virtual_size_}, process{GetCurrentProcess()},
          kernelbase_dll("Kernelbase") {
        if (!kernelbase_dll.IsOpen()) {
            LOG_CRITICAL(HW_Memory, "Failed to load Kernelbase.dll");
            throw std::bad_alloc{};
        }
        GetFuncAddress(kernelbase_dll, "CreateFileMapping2", pfn_CreateFileMapping2);
        GetFuncAddress(kernelbase_dll, "VirtualAlloc2", pfn_VirtualAlloc2);
        GetFuncAddress(kernelbase_dll, "MapViewOfFile3", pfn_MapViewOfFile3);
        GetFuncAddress(kernelbase_dll, "UnmapViewOfFile2", pfn_UnmapViewOfFile2);

        // Allocate backing file map
        backing_handle =
            pfn_CreateFileMapping2(INVALID_HANDLE_VALUE, nullptr, FILE_MAP_WRITE | FILE_MAP_READ,
                                   PAGE_READWRITE, SEC_COMMIT, backing_size, nullptr, nullptr, 0);
        if (!backing_handle) {
            LOG_CRITICAL(HW_Memory, "Failed to allocate {} MiB of backing memory",
                         backing_size >> 20);
            throw std::bad_alloc{};
        }
        // Allocate a virtual memory for the backing file map as placeholder
        backing_base = static_cast<u8*>(pfn_VirtualAlloc2(process, nullptr, backing_size,
                                                          MEM_RESERVE | MEM_RESERVE_PLACEHOLDER,
                                                          PAGE_NOACCESS, nullptr, 0));
        if (!backing_base) {
            Release();
            LOG_CRITICAL(HW_Memory, "Failed to reserve {} MiB of virtual memory",
                         backing_size >> 20);
            throw std::bad_alloc{};
        }
        // Map backing placeholder
        void* const ret = pfn_MapViewOfFile3(backing_handle, process, backing_base, 0, backing_size,
                                             MEM_REPLACE_PLACEHOLDER, PAGE_READWRITE, nullptr, 0);
        if (ret != backing_base) {
            Release();
            LOG_CRITICAL(HW_Memory, "Failed to map {} MiB of virtual memory", backing_size >> 20);
            throw std::bad_alloc{};
        }
        // Allocate virtual address placeholder
        virtual_base = static_cast<u8*>(pfn_VirtualAlloc2(process, nullptr, virtual_size,
                                                          MEM_RESERVE | MEM_RESERVE_PLACEHOLDER,
                                                          PAGE_NOACCESS, nullptr, 0));
        if (!virtual_base) {
            Release();
            LOG_CRITICAL(HW_Memory, "Failed to reserve {} GiB of virtual memory",
                         virtual_size >> 30);
            throw std::bad_alloc{};
        }
    }

    ~Impl() {
        Release();
    }

    void Map(size_t virtual_offset, size_t host_offset, size_t length) {
        std::unique_lock lock{placeholder_mutex};
        if (!IsNiechePlaceholder(virtual_offset, length)) {
            Split(virtual_offset, length);
        }
        ASSERT(placeholders.find({virtual_offset, virtual_offset + length}) == placeholders.end());
        TrackPlaceholder(virtual_offset, host_offset, length);

        MapView(virtual_offset, host_offset, length);
    }

    void Unmap(size_t virtual_offset, size_t length) {
        std::scoped_lock lock{placeholder_mutex};

        // Unmap until there are no more placeholders
        while (UnmapOnePlaceholder(virtual_offset, length)) {
        }
    }

    void Protect(size_t virtual_offset, size_t length, bool read, bool write) {
        DWORD new_flags{};
        if (read && write) {
            new_flags = PAGE_READWRITE;
        } else if (read && !write) {
            new_flags = PAGE_READONLY;
        } else if (!read && !write) {
            new_flags = PAGE_NOACCESS;
        } else {
            UNIMPLEMENTED_MSG("Protection flag combination read={} write={}", read, write);
        }
        const size_t virtual_end = virtual_offset + length;

        std::scoped_lock lock{placeholder_mutex};
        auto [it, end] = placeholders.equal_range({virtual_offset, virtual_end});
        while (it != end) {
            const size_t offset = std::max(it->lower(), virtual_offset);
            const size_t protect_length = std::min(it->upper(), virtual_end) - offset;
            DWORD old_flags{};
            if (!VirtualProtect(virtual_base + offset, protect_length, new_flags, &old_flags)) {
                LOG_CRITICAL(HW_Memory, "Failed to change virtual memory protect rules");
            }
            ++it;
        }
    }

    const size_t backing_size; ///< Size of the backing memory in bytes
    const size_t virtual_size; ///< Size of the virtual address placeholder in bytes

    u8* backing_base{};
    u8* virtual_base{};

private:
    /// Release all resources in the object
    void Release() {
        if (!placeholders.empty()) {
            for (const auto& placeholder : placeholders) {
                if (!pfn_UnmapViewOfFile2(process, virtual_base + placeholder.lower(),
                                          MEM_PRESERVE_PLACEHOLDER)) {
                    LOG_CRITICAL(HW_Memory, "Failed to unmap virtual memory placeholder");
                }
            }
            Coalesce(0, virtual_size);
        }
        if (virtual_base) {
            if (!VirtualFree(virtual_base, 0, MEM_RELEASE)) {
                LOG_CRITICAL(HW_Memory, "Failed to free virtual memory");
            }
        }
        if (backing_base) {
            if (!pfn_UnmapViewOfFile2(process, backing_base, MEM_PRESERVE_PLACEHOLDER)) {
                LOG_CRITICAL(HW_Memory, "Failed to unmap backing memory placeholder");
            }
            if (!VirtualFreeEx(process, backing_base, 0, MEM_RELEASE)) {
                LOG_CRITICAL(HW_Memory, "Failed to free backing memory");
            }
        }
        if (!CloseHandle(backing_handle)) {
            LOG_CRITICAL(HW_Memory, "Failed to free backing memory file handle");
        }
    }

    /// Unmap one placeholder in the given range (partial unmaps are supported)
    /// Return true when there are no more placeholders to unmap
    bool UnmapOnePlaceholder(size_t virtual_offset, size_t length) {
        const auto it = placeholders.find({virtual_offset, virtual_offset + length});
        const auto begin = placeholders.begin();
        const auto end = placeholders.end();
        if (it == end) {
            return false;
        }
        const size_t placeholder_begin = it->lower();
        const size_t placeholder_end = it->upper();
        const size_t unmap_begin = std::max(virtual_offset, placeholder_begin);
        const size_t unmap_end = std::min(virtual_offset + length, placeholder_end);
        ASSERT(unmap_begin >= placeholder_begin && unmap_begin < placeholder_end);
        ASSERT(unmap_end <= placeholder_end && unmap_end > placeholder_begin);

        const auto host_pointer_it = placeholder_host_pointers.find(placeholder_begin);
        ASSERT(host_pointer_it != placeholder_host_pointers.end());
        const size_t host_offset = host_pointer_it->second;

        const bool split_left = unmap_begin > placeholder_begin;
        const bool split_right = unmap_end < placeholder_end;

        if (!pfn_UnmapViewOfFile2(process, virtual_base + placeholder_begin,
                                  MEM_PRESERVE_PLACEHOLDER)) {
            LOG_CRITICAL(HW_Memory, "Failed to unmap placeholder");
        }
        // If we have to remap memory regions due to partial unmaps, we are in a data race as
        // Windows doesn't support remapping memory without unmapping first. Avoid adding any extra
        // logic within the panic region described below.

        // Panic region, we are in a data race right now
        if (split_left || split_right) {
            Split(unmap_begin, unmap_end - unmap_begin);
        }
        if (split_left) {
            MapView(placeholder_begin, host_offset, unmap_begin - placeholder_begin);
        }
        if (split_right) {
            MapView(unmap_end, host_offset + unmap_end - placeholder_begin,
                    placeholder_end - unmap_end);
        }
        // End panic region

        size_t coalesce_begin = unmap_begin;
        if (!split_left) {
            // Try to coalesce pages to the left
            coalesce_begin = it == begin ? 0 : std::prev(it)->upper();
            if (coalesce_begin != placeholder_begin) {
                Coalesce(coalesce_begin, unmap_end - coalesce_begin);
            }
        }
        if (!split_right) {
            // Try to coalesce pages to the right
            const auto next = std::next(it);
            const size_t next_begin = next == end ? virtual_size : next->lower();
            if (placeholder_end != next_begin) {
                // We can coalesce to the right
                Coalesce(coalesce_begin, next_begin - coalesce_begin);
            }
        }
        // Remove and reinsert placeholder trackers
        UntrackPlaceholder(it);
        if (split_left) {
            TrackPlaceholder(placeholder_begin, host_offset, unmap_begin - placeholder_begin);
        }
        if (split_right) {
            TrackPlaceholder(unmap_end, host_offset + unmap_end - placeholder_begin,
                             placeholder_end - unmap_end);
        }
        return true;
    }

    void MapView(size_t virtual_offset, size_t host_offset, size_t length) {
        if (!pfn_MapViewOfFile3(backing_handle, process, virtual_base + virtual_offset, host_offset,
                                length, MEM_REPLACE_PLACEHOLDER, PAGE_READWRITE, nullptr, 0)) {
            LOG_CRITICAL(HW_Memory, "Failed to map placeholder");
        }
    }

    void Split(size_t virtual_offset, size_t length) {
        if (!VirtualFreeEx(process, reinterpret_cast<LPVOID>(virtual_base + virtual_offset), length,
                           MEM_RELEASE | MEM_PRESERVE_PLACEHOLDER)) {
            LOG_CRITICAL(HW_Memory, "Failed to split placeholder");
        }
    }

    void Coalesce(size_t virtual_offset, size_t length) {
        if (!VirtualFreeEx(process, reinterpret_cast<LPVOID>(virtual_base + virtual_offset), length,
                           MEM_RELEASE | MEM_COALESCE_PLACEHOLDERS)) {
            LOG_CRITICAL(HW_Memory, "Failed to coalesce placeholders");
        }
    }

    void TrackPlaceholder(size_t virtual_offset, size_t host_offset, size_t length) {
        placeholders.insert({virtual_offset, virtual_offset + length});
        placeholder_host_pointers.emplace(virtual_offset, host_offset);
    }

    void UntrackPlaceholder(boost::icl::separate_interval_set<size_t>::iterator it) {
        placeholder_host_pointers.erase(it->lower());
        placeholders.erase(it);
    }

    /// Return true when a given memory region is a "nieche" and the placeholders don't have to be
    /// split.
    bool IsNiechePlaceholder(size_t virtual_offset, size_t length) const {
        const auto it = placeholders.upper_bound({virtual_offset, virtual_offset + length});
        if (it != placeholders.end() && it->lower() == virtual_offset + length) {
            return it == placeholders.begin() ? virtual_offset == 0
                                              : std::prev(it)->upper() == virtual_offset;
        }
        return false;
    }

    HANDLE process{};        ///< Current process handle
    HANDLE backing_handle{}; ///< File based backing memory

    DynamicLibrary kernelbase_dll;
    PFN_CreateFileMapping2 pfn_CreateFileMapping2{};
    PFN_VirtualAlloc2 pfn_VirtualAlloc2{};
    PFN_MapViewOfFile3 pfn_MapViewOfFile3{};
    PFN_UnmapViewOfFile2 pfn_UnmapViewOfFile2{};

    std::mutex placeholder_mutex;                                 ///< Mutex for placeholders
    boost::icl::separate_interval_set<size_t> placeholders;       ///< Mapped placeholders
    std::unordered_map<size_t, size_t> placeholder_host_pointers; ///< Placeholder backing offset
};

#elif defined(__linux__) || defined(__FreeBSD__) // ^^^ Windows ^^^ vvv Linux vvv

class HostMemory::Impl {
public:
    explicit Impl(size_t backing_size_, size_t virtual_size_)
        : backing_size{backing_size_}, virtual_size{virtual_size_} {
        bool good = false;
        SCOPE_EXIT({
            if (!good) {
                Release();
            }
        });

        long page_size = sysconf(_SC_PAGESIZE);
        if (page_size != 0x1000) {
            LOG_CRITICAL(HW_Memory, "page size {:#x} is incompatible with 4K paging", page_size);
            throw std::bad_alloc{};
        }

        // Backing memory initialization
#ifdef ANDROID
        fd = ASharedMemory_create("HostMemory", backing_size);
#elif defined(__FreeBSD__) && __FreeBSD__ < 13
        // XXX Drop after FreeBSD 12.* reaches EOL on 2024-06-30
        fd = shm_open(SHM_ANON, O_RDWR, 0600);
#else
        fd = memfd_create("HostMemory", 0);
#endif
        if (fd < 0) {
            LOG_CRITICAL(HW_Memory, "memfd_create failed: {}", strerror(errno));
            throw std::bad_alloc{};
        }

#ifndef ANDROID
        // Defined to extend the file with zeros
        int ret = ftruncate(fd, backing_size);
        if (ret != 0) {
            LOG_CRITICAL(HW_Memory, "ftruncate failed with {}, are you out-of-memory?",
                         strerror(errno));
            throw std::bad_alloc{};
        }
#endif

        backing_base = static_cast<u8*>(
            mmap(nullptr, backing_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0));
        if (backing_base == MAP_FAILED) {
            LOG_CRITICAL(HW_Memory, "mmap failed: {}", strerror(errno));
            throw std::bad_alloc{};
        }

        // Virtual memory initialization
#if defined(__FreeBSD__)
        virtual_base =
            static_cast<u8*>(mmap(nullptr, virtual_size, PROT_NONE,
                                  MAP_PRIVATE | MAP_ANONYMOUS | MAP_ALIGNED_SUPER, -1, 0));
        if (virtual_base == MAP_FAILED) {
            virtual_base = static_cast<u8*>(
                mmap(nullptr, virtual_size, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
            if (virtual_base == MAP_FAILED) {
                LOG_CRITICAL(HW_Memory, "mmap failed: {}", strerror(errno));
                throw std::bad_alloc{};
            }
        }
#else
        virtual_base = static_cast<u8*>(mmap(nullptr, virtual_size, PROT_NONE,
                                             MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0));
        if (virtual_base == MAP_FAILED) {
            LOG_CRITICAL(HW_Memory, "mmap failed: {}", strerror(errno));
            throw std::bad_alloc{};
        }
        madvise(virtual_base, virtual_size, MADV_HUGEPAGE);
#endif

        placeholders.add({0, virtual_size});
        good = true;
    }

    ~Impl() {
        Release();
    }

    void Map(size_t virtual_offset, size_t host_offset, size_t length) {
        {
            std::scoped_lock lock{placeholder_mutex};
            placeholders.subtract({virtual_offset, virtual_offset + length});
        }

        void* ret = mmap(virtual_base + virtual_offset, length, PROT_READ | PROT_WRITE,
                         MAP_SHARED | MAP_FIXED, fd, host_offset);
        ASSERT_MSG(ret != MAP_FAILED, "mmap failed: {}", strerror(errno));
    }

    void Unmap(size_t virtual_offset, size_t length) {
        // The method name is wrong. We're still talking about the virtual range.
        // We don't want to unmap, we want to reserve this memory.

        {
            std::scoped_lock lock{placeholder_mutex};
            auto it = placeholders.find({virtual_offset - 1, virtual_offset + length + 1});

            if (it != placeholders.end()) {
                size_t prev_upper = virtual_offset + length;
                virtual_offset = std::min(virtual_offset, it->lower());
                length = std::max(it->upper(), prev_upper) - virtual_offset;
            }

            placeholders.add({virtual_offset, virtual_offset + length});
        }

        void* ret = mmap(virtual_base + virtual_offset, length, PROT_NONE,
                         MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
        ASSERT_MSG(ret != MAP_FAILED, "mmap failed: {}", strerror(errno));
    }

    void Protect(size_t virtual_offset, size_t length, bool read, bool write) {
        int flags = 0;
        if (read) {
            flags |= PROT_READ;
        }
        if (write) {
            flags |= PROT_WRITE;
        }
        int ret = mprotect(virtual_base + virtual_offset, length, flags);
        ASSERT_MSG(ret == 0, "mprotect failed: {}", strerror(errno));
    }

    const size_t backing_size; ///< Size of the backing memory in bytes
    const size_t virtual_size; ///< Size of the virtual address placeholder in bytes

    u8* backing_base{reinterpret_cast<u8*>(MAP_FAILED)};
    u8* virtual_base{reinterpret_cast<u8*>(MAP_FAILED)};

private:
    /// Release all resources in the object
    void Release() {
        if (virtual_base != MAP_FAILED) {
            int ret = munmap(virtual_base, virtual_size);
            ASSERT_MSG(ret == 0, "munmap failed: {}", strerror(errno));
        }

        if (backing_base != MAP_FAILED) {
            int ret = munmap(backing_base, backing_size);
            ASSERT_MSG(ret == 0, "munmap failed: {}", strerror(errno));
        }

        if (fd != -1) {
            int ret = close(fd);
            ASSERT_MSG(ret == 0, "close failed: {}", strerror(errno));
        }
    }

    int fd{-1}; // memfd file descriptor, -1 is the error value of memfd_create

    boost::icl::interval_set<size_t> placeholders; ///< Mapped placeholders
    std::mutex placeholder_mutex;                  ///< Mutex for placeholders
};

#else // ^^^ Linux ^^^ vvv Generic vvv

class HostMemory::Impl {
public:
    explicit Impl(size_t /*backing_size */, size_t /* virtual_size */) {
        // This is just a place holder.
        // Please implement fastmem in a proper way on your platform.
        throw std::bad_alloc{};
    }

    void Map(size_t virtual_offset, size_t host_offset, size_t length) {}

    void Unmap(size_t virtual_offset, size_t length) {}

    void Protect(size_t virtual_offset, size_t length, bool read, bool write) {}

    u8* backing_base{nullptr};
    u8* virtual_base{nullptr};
};

#endif // ^^^ Generic ^^^

HostMemory::HostMemory(size_t backing_size_, size_t virtual_size_)
    : backing_size(backing_size_), virtual_size(virtual_size_) {
    try {
        // Try to allocate a fastmem arena.
        // The implementation will fail with std::bad_alloc on errors.
        impl = std::make_unique<HostMemory::Impl>(AlignUp(backing_size, PageAlignment),
                                                  AlignUp(virtual_size, PageAlignment) +
                                                      3 * HugePageSize);
        backing_base = impl->backing_base;
        virtual_base = impl->virtual_base;

        if (virtual_base) {
            virtual_base += 2 * HugePageSize - 1;
            virtual_base -= reinterpret_cast<size_t>(virtual_base) & (HugePageSize - 1);
            virtual_base_offset = virtual_base - impl->virtual_base;
        }

    } catch (const std::bad_alloc&) {
        LOG_CRITICAL(HW_Memory,
                     "Fastmem unavailable, falling back to VirtualBuffer for memory allocation");
        fallback_buffer = std::make_unique<Common::VirtualBuffer<u8>>(backing_size);
        backing_base = fallback_buffer->data();
        virtual_base = nullptr;
    }
}

HostMemory::~HostMemory() = default;

HostMemory::HostMemory(HostMemory&&) noexcept = default;

HostMemory& HostMemory::operator=(HostMemory&&) noexcept = default;

void HostMemory::Map(size_t virtual_offset, size_t host_offset, size_t length) {
    ASSERT(virtual_offset % PageAlignment == 0);
    ASSERT(host_offset % PageAlignment == 0);
    ASSERT(length % PageAlignment == 0);
    ASSERT(virtual_offset + length <= virtual_size);
    ASSERT(host_offset + length <= backing_size);
    if (length == 0 || !virtual_base || !impl) {
        return;
    }
    impl->Map(virtual_offset + virtual_base_offset, host_offset, length);
}

void HostMemory::Unmap(size_t virtual_offset, size_t length) {
    ASSERT(virtual_offset % PageAlignment == 0);
    ASSERT(length % PageAlignment == 0);
    ASSERT(virtual_offset + length <= virtual_size);
    if (length == 0 || !virtual_base || !impl) {
        return;
    }
    impl->Unmap(virtual_offset + virtual_base_offset, length);
}

void HostMemory::Protect(size_t virtual_offset, size_t length, bool read, bool write) {
    ASSERT(virtual_offset % PageAlignment == 0);
    ASSERT(length % PageAlignment == 0);
    ASSERT(virtual_offset + length <= virtual_size);
    if (length == 0 || !virtual_base || !impl) {
        return;
    }
    impl->Protect(virtual_offset + virtual_base_offset, length, read, write);
}

} // namespace Common