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author | bunnei <bunneidev@gmail.com> | 2021-01-01 11:54:01 +0100 |
---|---|---|
committer | GitHub <noreply@github.com> | 2021-01-01 11:54:01 +0100 |
commit | eb318ffffc5007c35c42826e23945a82c24900b1 (patch) | |
tree | 95a401077534f48f0e6a92a269321ff9ad7aec45 /src/common/page_table.h | |
parent | Merge pull request #5239 from FearlessTobi/enable-translation (diff) | |
parent | core/memory: Read and write page table atomically (diff) | |
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Diffstat (limited to 'src/common/page_table.h')
-rw-r--r-- | src/common/page_table.h | 68 |
1 files changed, 57 insertions, 11 deletions
diff --git a/src/common/page_table.h b/src/common/page_table.h index 9754fabf9..8d4ee9249 100644 --- a/src/common/page_table.h +++ b/src/common/page_table.h @@ -4,6 +4,7 @@ #pragma once +#include <atomic> #include <tuple> #include "common/common_types.h" @@ -20,10 +21,6 @@ enum class PageType : u8 { /// Page is mapped to regular memory, but also needs to check for rasterizer cache flushing and /// invalidation RasterizerCachedMemory, - /// Page is mapped to a I/O region. Writing and reading to this page is handled by functions. - Special, - /// Page is allocated for use. - Allocated, }; struct SpecialRegion { @@ -48,6 +45,59 @@ struct SpecialRegion { * 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; @@ -63,20 +113,16 @@ struct PageTable { * * @param address_space_width_in_bits The address size width in bits. * @param page_size_in_bits The page size in bits. - * @param has_attribute Whether or not this page has any backing attributes. */ - void Resize(std::size_t address_space_width_in_bits, std::size_t page_size_in_bits, - bool has_attribute); + void Resize(size_t address_space_width_in_bits, size_t page_size_in_bits); /** * Vector of memory pointers backing each page. An entry can only be non-null if the - * corresponding entry in the `attributes` vector is of type `Memory`. + * corresponding attribute element is of type `Memory`. */ - VirtualBuffer<u8*> pointers; + VirtualBuffer<PageInfo> pointers; VirtualBuffer<u64> backing_addr; - - VirtualBuffer<PageType> attributes; }; } // namespace Common |