An in-flight patch[1] to make __kvm_handle_fault_on_reboot() play nice with objtool will add a JMP after most VMX instructions so that the reboot macro can use an actual CALL to kvm_spurious_fault() instead of a funky PUSH+JMP facsimile. Rework the low level VMX instruction helpers to handle unexpected faults manually instead of relying on the "fault on reboot" macro. By using asm-goto, most helpers can branch directly to an in-function call to kvm_spurious_fault(), which can then be optimized by compilers to reside out-of-line at the end of the function instead of inline as done by "fault on reboot". The net impact relative to the current code base is more or less a nop when building with a compiler that supports __GCC_ASM_FLAG_OUTPUTS__. A bunch of code that was previously in .fixup gets moved into the slow paths of functions, but the fast paths are more basically unchanged. Without __GCC_ASM_FLAG_OUTPUTS__, manually coding the Jcc is a net positive as CC_SET() without compiler support almost always generates a SETcc+CMP+Jcc sequence, which is now replaced with a single Jcc. A small bonus is that the Jcc instrs are hinted to predict that the VMX instr will be successful. [1] https://lkml.kernel.org/r/64a9b64d127e87b6920a97afde8e96ea76f6524e.1563413318.git.jpoimboe@xxxxxxxxxx Sean Christopherson (4): objtool: KVM: x86: Check kvm_rebooting in kvm_spurious_fault() KVM: VMX: Optimize VMX instruction error and fault handling KVM: VMX: Add error handling to VMREAD helper KVM: x86: Drop ____kvm_handle_fault_on_reboot() arch/x86/include/asm/kvm_host.h | 6 +-- arch/x86/kvm/vmx/ops.h | 93 ++++++++++++++++++++------------- arch/x86/kvm/vmx/vmx.c | 42 +++++++++++++++ arch/x86/kvm/x86.c | 3 +- tools/objtool/check.c | 1 - 5 files changed, 102 insertions(+), 43 deletions(-) -- 2.22.0
