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Kernel: Don't read CR registers on every exception

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Bananymous
2026-06-26 01:39:57 +03:00
parent 59ec05c898
commit 2bb9b9b4b3
8 changed files with 94 additions and 33 deletions
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53
kernel/kernel/Timer/Timer.cpp
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@@ -11,6 +11,18 @@ namespace Kernel
static SystemTimer* s_instance = nullptr;
struct pvclock_vcpu_time_info
{
uint32_t version;
uint32_t pad0;
uint64_t tsc_timestamp;
uint64_t system_time;
uint32_t tsc_to_system_mul;
int8_t tsc_shift;
uint8_t flags;
uint8_t pad[2];
};
void SystemTimer::initialize()
{
ASSERT(s_instance == nullptr);
@@ -59,6 +71,8 @@ namespace Kernel
void SystemTimer::initialize_tsc()
{
if (CPUID::has_kvm_pvclock())
return initialize_pvclock();
if (CPUID::has_invariant_tsc())
return initialize_invariant_tsc();
dwarnln("No supported TSC based timers available");
@@ -108,6 +122,39 @@ namespace Kernel
dprintln("Initialized invariant TSC ({} Hz)", tsc_freq);
}
static pvclock_vcpu_time_info read_pvclock_safe(vaddr_t pvclock_vaddr)
{
for (;;)
{
const volatile auto& pvclock = *reinterpret_cast<const volatile pvclock_vcpu_time_info*>(pvclock_vaddr);
const auto version = pvclock.version;
if (version & 1)
continue;
pvclock_vcpu_time_info copy;
memcpy(&copy, const_cast<const pvclock_vcpu_time_info*>(&pvclock), sizeof(pvclock_vcpu_time_info));
if (pvclock.version == version)
return copy;
}
}
void SystemTimer::initialize_pvclock()
{
m_tsc_page = MUST(DMARegion::create(sizeof(pvclock_vcpu_time_info), PageTable::MemoryType::Normal));
memset(reinterpret_cast<void*>(m_tsc_page->vaddr()), 0, sizeof(pvclock_vcpu_time_info));
const uint32_t paddr_hi = m_tsc_page->paddr() >> 32;
const uint32_t paddr_lo = m_tsc_page->paddr() & 0xFFFFFFFF;
asm volatile("wrmsr" :: "d"(paddr_hi), "a"(paddr_lo | 1), "c"(0x4b564d01));
m_tsc_type = TSCType::PVClock;
Processor::initialize_tsc(m_boot_time);
dprintln("Initialized pvclock");
}
void SystemTimer::update_tsc()
{
if (m_tsc_type == TSCType::None)
@@ -137,6 +184,12 @@ namespace Kernel
.shift = m_tsc_info.invariant.shift,
.mult = m_tsc_info.invariant.mult,
};
case TSCType::PVClock:
const auto pvclock = read_pvclock_safe(m_tsc_page->vaddr());
return {
.shift = pvclock.tsc_shift,
.mult = pvclock.tsc_to_system_mul,
};
}
ASSERT_NOT_REACHED();
}