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Merged
fwsGonzo merged 2 commits into from
Oct 24, 2025
Merged

Open existing snapshot file readonly and include size of accessed pages #58

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accd0a5
Open existing snapshot file readonly
lrowe Oct 22, 2025
59c0a12
include size of accessed pages
lrowe Oct 24, 2025
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10 changes: 5 additions & 5 deletions lib/tinykvm/amd64/paging.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -531,13 +531,13 @@ void foreach_page_makecow(vMemory& mem, uint64_t kernel_end, uint64_t shared_mem
entry &= ~PDE64_ACCESSED;
});
}
std::vector<uint64_t> get_accessed_pages(const vMemory& memory)
std::vector<std::pair<uint64_t, uint64_t>> get_accessed_pages(const vMemory& memory)
{
std::vector<uint64_t> accessed_pages;
std::vector<std::pair<uint64_t, uint64_t>> accessed_pages;
foreach_page(memory,
[&accessed_pages] (uint64_t addr, uint64_t& entry, size_t /*size*/) {
if ((entry & (PDE64_ACCESSED | PDE64_PRESENT)) == (PDE64_ACCESSED | PDE64_PRESENT)) {
accessed_pages.push_back(addr & PDE64_ADDR_MASK);
[&accessed_pages] (uint64_t addr, uint64_t& entry, size_t size) {
if ((entry & (PDE64_PS | PDE64_ACCESSED | PDE64_PRESENT)) == (PDE64_PS | PDE64_ACCESSED | PDE64_PRESENT)) {
accessed_pages.push_back({addr & PDE64_ADDR_MASK, size});
}
}, false);
return accessed_pages;
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2 changes: 1 addition & 1 deletion lib/tinykvm/amd64/paging.hpp
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Expand Up @@ -14,7 +14,7 @@ using foreach_page_t = std::function<void(uint64_t, uint64_t&, size_t)>;
extern void foreach_page(vMemory&, foreach_page_t callback, bool skip_oob_addresses = true);
extern void foreach_page(const vMemory&, foreach_page_t callback, bool skip_oob_addresses = true);
extern void foreach_page_makecow(vMemory&, uint64_t kernel_end, uint64_t shared_memory_boundary);
extern std::vector<uint64_t> get_accessed_pages(const vMemory& memory);
extern std::vector<std::pair<uint64_t, uint64_t>> get_accessed_pages(const vMemory& memory);

extern void page_at(vMemory&, uint64_t addr, foreach_page_t, bool ignore_missing = false);
struct WritablePage {
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4 changes: 2 additions & 2 deletions lib/tinykvm/machine.hpp
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Expand Up @@ -245,7 +245,7 @@ struct Machine
void set_main_memory_writable(bool v) { memory.main_memory_writes = v; }
bool is_forked() const noexcept { return m_forked; }
bool uses_cow_memory() const noexcept { return m_forked || m_prepped; }
std::vector<uint64_t> get_accessed_pages() const;
std::vector<std::pair<uint64_t, uint64_t>> get_accessed_pages() const;

/* Remote VM through address space merging */
void remote_connect(Machine& other, bool connect_now = false);
Expand Down Expand Up @@ -299,7 +299,7 @@ struct Machine
/* Store non-memory VM state to the already existing cold
start state area in memory. Any failure will throw an
exception. The memory must have been pre-allocated. */
void save_snapshot_state_now(const std::vector<uint64_t>& populate_pages = {}) const;
void save_snapshot_state_now(const std::vector<std::pair<uint64_t, uint64_t>>& populate_pages = {}) const;
/* Check if the VM was loaded from a snapshot state. */
bool has_snapshot_state() const noexcept { return m_loaded_from_snapshot; }
/* Get pointer to user area in snapshot state memory, or nullptr
Expand Down
8 changes: 4 additions & 4 deletions lib/tinykvm/machine_state.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -208,7 +208,7 @@ bool Machine::load_snapshot_state()
}
return true;
}
void Machine::save_snapshot_state_now(const std::vector<uint64_t>& populate_pages) const
void Machine::save_snapshot_state_now(const std::vector<std::pair<uint64_t, uint64_t>>& populate_pages) const
{
if (this->is_forked()) {
throw std::runtime_error("Cannot save snapshot state of a forked VM");
Expand Down Expand Up @@ -242,12 +242,12 @@ void Machine::save_snapshot_state_now(const std::vector<uint64_t>& populate_page
if (!populate_pages.empty()) {
uint64_t current_begin = 0;
uint64_t current_end = 0;
for (uint64_t page_addr : populate_pages) {
for (const auto& [page_addr, size] : populate_pages) {
if (page_addr >= MemoryBanks::ARENA_BASE_ADDRESS || page_addr < kernel_end_address())
continue;
// Merge contiguous ranges
if (current_end == page_addr) {
current_end += vMemory::PageSize();
current_end += size;
continue;
}
// Store previous range
Expand All @@ -259,7 +259,7 @@ void Machine::save_snapshot_state_now(const std::vector<uint64_t>& populate_page
}
// Start new range
current_begin = page_addr;
current_end = page_addr;
current_end = page_addr + size;
}
// Store last range
if (current_end != current_begin) {
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12 changes: 9 additions & 3 deletions lib/tinykvm/memory.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -397,9 +397,15 @@ vMemory::AllocationResult
if (filename.empty()) {
throw std::runtime_error("No VM snapshot file specified");
}
const int fd = open(filename.c_str(), O_RDWR | O_CREAT | O_CLOEXEC, 0600);
int fd = open(filename.c_str(), O_RDONLY | O_CLOEXEC);
if (fd < 0) {
throw std::runtime_error("Failed to open VM snapshot file: " + filename);
if (errno != ENOENT) {
throw std::runtime_error("Failed to open VM snapshot file: " + filename);
}
fd = open(filename.c_str(), O_RDWR | O_CREAT | O_CLOEXEC, 0600);
if (fd < 0) {
throw std::runtime_error("Failed to create VM snapshot file: " + filename);
}
}
struct stat st;
if (fstat(fd, &st) != 0) {
Expand Down Expand Up @@ -512,7 +518,7 @@ char* vMemory::get_userpage_at(uint64_t addr) const
#endif
}

std::vector<uint64_t> Machine::get_accessed_pages() const
std::vector<std::pair<uint64_t, uint64_t>> Machine::get_accessed_pages() const
{
return tinykvm::get_accessed_pages(this->main_memory());
}
Expand Down