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Kernel: Do not disable userland access to the RDTSC instruction

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Access to RDTSC is occasionally restricted to give malware one less
option to accurately time attacks (side-channels, etc.).

However, QEMU requires access to the timestamp counter for the exact
same reason (which is accurately timing its CPU ticks), so lets just
enable it for now.
This commit is contained in:
Tim Schumacher 2022-05-05 18:33:29 +02:00 • committed by Brian Gianforcaro
parent 9e8c698ae8
commit 7d3f71a648
1 changed files with 0 additions and 4 deletions
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4
Kernel/Arch/x86/common/Processor.cpp
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@ -551,10 +551,6 @@ UNMAP_AFTER_INIT void Processor::cpu_setup()
write_cr4(read_cr4() | 0x800);
}
if (has_feature(CPUFeature::TSC)) {
write_cr4(read_cr4() | 0x4);
}
if (has_feature(CPUFeature::XSAVE)) {
// Turn on CR4.OSXSAVE
write_cr4(read_cr4() | 0x40000);