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// Copyright 2019 yuzu Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.
#pragma once
#include <atomic>
#include <tuple>
#include "common/common_types.h"
#include "common/virtual_buffer.h"
namespace Common {
enum class PageType : u8 {
/// Page is unmapped and should cause an access error.
Unmapped,
/// Page is mapped to regular memory. This is the only type you can get pointers to.
Memory,
/// Page is mapped to regular memory, but also needs to check for rasterizer cache flushing and
/// invalidation
RasterizerCachedMemory,
};
/**
* A (reasonably) fast way of allowing switchable and remappable process address spaces. It loosely
* mimics the way a real CPU page table works.
*/
struct PageTable {
/// Number of bits reserved for attribute tagging.
/// This can be at most the guaranteed alignment of the pointers in the page table.
static constexpr int ATTRIBUTE_BITS = 2;
/**
* Pair of host pointer and page type attribute.
* This uses the lower bits of a given pointer to store the attribute tag.
* Writing and reading the pointer attribute pair is guaranteed to be atomic for the same method
* call. In other words, they are guaranteed to be synchronized at all times.
*/
class PageInfo {
public:
/// Returns the page pointer
[[nodiscard]] u8* Pointer() const noexcept {
return ExtractPointer(raw.load(std::memory_order_relaxed));
}
/// Returns the page type attribute
[[nodiscard]] PageType Type() const noexcept {
return ExtractType(raw.load(std::memory_order_relaxed));
}
/// Returns the page pointer and attribute pair, extracted from the same atomic read
[[nodiscard]] std::pair<u8*, PageType> PointerType() const noexcept {
const uintptr_t non_atomic_raw = raw.load(std::memory_order_relaxed);
return {ExtractPointer(non_atomic_raw), ExtractType(non_atomic_raw)};
}
/// Returns the raw representation of the page information.
/// Use ExtractPointer and ExtractType to unpack the value.
[[nodiscard]] uintptr_t Raw() const noexcept {
return raw.load(std::memory_order_relaxed);
}
/// Write a page pointer and type pair atomically
void Store(u8* pointer, PageType type) noexcept {
raw.store(reinterpret_cast<uintptr_t>(pointer) | static_cast<uintptr_t>(type));
}
/// Unpack a pointer from a page info raw representation
[[nodiscard]] static u8* ExtractPointer(uintptr_t raw) noexcept {
return reinterpret_cast<u8*>(raw & (~uintptr_t{0} << ATTRIBUTE_BITS));
}
/// Unpack a page type from a page info raw representation
[[nodiscard]] static PageType ExtractType(uintptr_t raw) noexcept {
return static_cast<PageType>(raw & ((uintptr_t{1} << ATTRIBUTE_BITS) - 1));
}
private:
std::atomic<uintptr_t> raw;
};
PageTable();
~PageTable() noexcept;
PageTable(const PageTable&) = delete;
PageTable& operator=(const PageTable&) = delete;
PageTable(PageTable&&) noexcept = default;
PageTable& operator=(PageTable&&) noexcept = default;
/**
* Resizes the page table to be able to accommodate enough pages within
* a given address space.
*
* @param address_space_width_in_bits The address size width in bits.
* @param page_size_in_bits The page size in bits.
*/
void Resize(size_t address_space_width_in_bits, size_t page_size_in_bits);
size_t GetAddressSpaceBits() const {
return current_address_space_width_in_bits;
}
/**
* Vector of memory pointers backing each page. An entry can only be non-null if the
* corresponding attribute element is of type `Memory`.
*/
VirtualBuffer<PageInfo> pointers;
VirtualBuffer<u64> backing_addr;
size_t current_address_space_width_in_bits;
u8* fastmem_arena;
};
} // namespace Common
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