Fix KVM and ring0 compatibility with Go toolchain X15 zeroing. - #14460
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Fix KVM and ring0 compatibility with Go toolchain X15 zeroing.#14460copybara-service[bot] wants to merge 1 commit into
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Initialize FPU and XCR0 in assembly before entering Go code, switch %rip to the lower half before calling kernel syscall and exception trampolines, and zero X15 on assembly return paths. Zeroing X15 is necessary because after cl/970057336 it is now used for zeroing other memory. To support this, Go now reads runtime.x86HasAVX which is a RIP-relative load, which happens when calling into compiler-generated ABI0 wrappers. When executing from the upper half of the virtual address space where we don't have data pages mapped (like we do when calling kernelSyscall and kernelException), this becomes a problem so we need to transition to the lower half via jumpToUser. PiperOrigin-RevId: 972102646
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August 27, 2026 21:11
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Fix KVM and ring0 compatibility with Go toolchain X15 zeroing.
Initialize FPU and XCR0 in assembly before entering Go code, switch %rip
to the lower half before calling kernel syscall and exception
trampolines, and zero X15 on assembly return paths.
Zeroing X15 is necessary because after cl/970057336 it is now used for
zeroing other memory. To support this, Go now reads runtime.x86HasAVX which
is a RIP-relative load, which happens when calling into compiler-generated
ABI0 wrappers. When executing from the upper half of the virtual address space
where we don't have data pages mapped (like we do when calling kernelSyscall
and kernelException), this becomes a problem so we need to transition to the
lower half via jumpToUser.