page_walk_cache.hh

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/*
 * Copyright (c) 2025 Jason Lowe-Power
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#ifndef __ARCH_AMDGPU_VEGA_PAGE_WALK_CACHE_HH__
#define __ARCH_AMDGPU_VEGA_PAGE_WALK_CACHE_HH__
 
 
#include "arch/amdgpu/vega/pagetable.hh"
#include "base/cache/associative_cache.hh"
#include "mem/cache/replacement_policies/replaceable_entry.hh"
#include "mem/cache/tags/indexing_policies/set_associative.hh"
#include "params/VegaPWCIndexingPolicy.hh"
 
namespace gem5
{
 
 
namespace VegaISA
{
 
// Page walk cache entry
struct PWCEntry : public ReplaceableEntry
{
  public:
    using IndexingPolicy = VegaPWCIndexingPolicy;
    using KeyType = Addr;
 
    // The data stored in PTE
    PageTableEntry pteEntry;
 
    // The physical address of the page table entry
    Addr paddr;
 
    bool valid;
 
    void
    invalidate()
    {
        valid = false;
    }
 
    void insert(const KeyType &key) {}
    bool isValid() const { return valid; }
 
    bool
    match(const KeyType &key) const
    {
        return valid && paddr == key;
    }
};

class VegaPWCIndexingPolicy : public BaseIndexingPolicy
{
  protected:
    virtual uint32_t extractSet(const Addr addr) const
    {
        // Extract the set bits from the address
        return (addr >> setShift) & setMask;
    }
 
  public:
    typedef VegaPWCIndexingPolicyParams Params;

    VegaPWCIndexingPolicy(const Params &p) :
        BaseIndexingPolicy(p, p.entries, 3)
    {}

    ~VegaPWCIndexingPolicy() {};
 
    std::vector<ReplaceableEntry*> getPossibleEntries(const Addr &addr) const
                                                                     override
    {
        return sets[extractSet(addr)];
    }
 
    Addr regenerateAddr(const Addr &tag,
                        const ReplaceableEntry* entry) const override
    {
        panic("PWCSetAssociative::regenerateAddr() not implemented");
        return 0;
    }
};
 
// Page walk cache
class PageWalkCache : public AssociativeCache<PWCEntry>
{
  public:
    using AssociativeCache<PWCEntry>::AssociativeCache;
    using AssociativeCache<PWCEntry>::accessEntry;
 
    PWCEntry* accessEntry(const KeyType &key) override
    {
        auto entry = findEntry(key);
        accessEntry(entry);
        return entry;
    }
    PWCEntry* findEntry(const KeyType &key) const override
    {
        for (auto candidate : indexingPolicy->getPossibleEntries(key)) {
        auto entry = static_cast<PWCEntry*>(candidate);
        if (entry->match(key))
            return entry;
        }
        return nullptr;
    }
    void insert(const KeyType &key, const PageTableEntry &pte_entry) {
        PWCEntry *vict = findVictim(key);
        vict->pteEntry = pte_entry;
        vict->paddr = key;
        vict->valid = true;
        insertEntry(key, vict);
    }
};
 
} // namespace VegaISA
} // namespace gem5
 
#endif // __ARCH_AMDGPU_VEGA_PAGE_WALK_CACHE_HH__