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Kernel: Enable AVX flags if supported by cpu

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This enables AVX and its dependency CR4.OSXSAVE when both are available on the cpu.
This commit is contained in:
Ashleigh Newman-Jones 2021-03-01 21:50:50 +00:00 • committed by Andreas Kling
parent de9f458ff5
commit f0912027ff
2 changed files with 37 additions and 0 deletions
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33
Kernel/Arch/i386/CPU.cpp
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@ -829,6 +829,24 @@ FlatPtr read_dr6()
return dr6;
}
#define XCR_XFEATURE_ENABLED_MASK 0
UNMAP_AFTER_INIT u64 read_xcr0()
{
u32 eax, edx;
asm volatile("xgetbv"
: "=a"(eax), "=d"(edx)
: "c"(XCR_XFEATURE_ENABLED_MASK));
return eax + ((u64)edx << 32);
}
UNMAP_AFTER_INIT void write_xcr0(u64 value)
{
u32 eax = value;
u32 edx = value >> 32;
asm volatile("xsetbv" ::"a"(eax), "d"(edx), "c"(XCR_XFEATURE_ENABLED_MASK));
}
READONLY_AFTER_INIT FPUState Processor::s_clean_fpu_state;
READONLY_AFTER_INIT static Vector<Processor*>* s_processors;
@ -893,6 +911,10 @@ UNMAP_AFTER_INIT void Processor::cpu_detect()
set_feature(CPUFeature::SSE4_1);
if (processor_info.ecx() & (1 << 20))
set_feature(CPUFeature::SSE4_2);
if (processor_info.ecx() & (1 << 26))
set_feature(CPUFeature::XSAVE);
if (processor_info.ecx() & (1 << 28))
set_feature(CPUFeature::AVX);
if (processor_info.ecx() & (1 << 30))
set_feature(CPUFeature::RDRAND);
if (processor_info.edx() & (1 << 11)) {
@ -989,6 +1011,13 @@ UNMAP_AFTER_INIT void Processor::cpu_setup()
if (has_feature(CPUFeature::TSC)) {
write_cr4(read_cr4() | 0x4);
}
if (has_feature(CPUFeature::XSAVE) && has_feature(CPUFeature::AVX)) {
// Turn on CR4.OSXSAVE
write_cr4(read_cr4() | 0x40000);
// Turn on AVX flags
write_xcr0(read_xcr0() | 0x7);
}
}
String Processor::features_string() const
@ -1039,6 +1068,10 @@ String Processor::features_string() const
return "sse4.1";
case CPUFeature::SSE4_2:
return "sse4.2";
case CPUFeature::XSAVE:
return "xsave";
case CPUFeature::AVX:
return "avx";
// no default statement here intentionally so that we get
// a warning if a new feature is forgotten to be added here
}