From ac07ffc19d52e161c081de3aaa2b3dadf103a233 Mon Sep 17 00:00:00 2001 From: Andrea Arcangeli Date: Mon, 4 Nov 2019 17:59:59 -0500 Subject: [PATCH] KVM: retpolines: x86: eliminate retpoline from vmx.c exit handlers [ Upstream commit 6630f46e5338ef20c977b43e2a6e639bbb057681 ] It's enough to check the exit value and issue a direct call to avoid the retpoline for all the common vmexit reasons. Of course CONFIG_RETPOLINE already forbids gcc to use indirect jumps while compiling all switch() statements, however switch() would still allow the compiler to bisect the case value. It's more efficient to prioritize the most frequent vmexits instead. The halt may be slow paths from the point of the guest, but not necessarily so from the point of the host if the host runs at full CPU capacity and no host CPU is ever left idle. Signed-off-by: Andrea Arcangeli Signed-off-by: Paolo Bonzini Stable-dep-of: 31de69f4eea7 ("KVM: nVMX: Properly expose ENABLE_USR_WAIT_PAUSE control to L1") Signed-off-by: Sasha Levin --- arch/x86/kvm/vmx/vmx.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 0fae9b448ab9b..668505c6abe9f 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6015,9 +6015,23 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu) } if (exit_reason < kvm_vmx_max_exit_handlers - && kvm_vmx_exit_handlers[exit_reason]) + && kvm_vmx_exit_handlers[exit_reason]) { +#ifdef CONFIG_RETPOLINE + if (exit_reason == EXIT_REASON_MSR_WRITE) + return kvm_emulate_wrmsr(vcpu); + else if (exit_reason == EXIT_REASON_PREEMPTION_TIMER) + return handle_preemption_timer(vcpu); + else if (exit_reason == EXIT_REASON_PENDING_INTERRUPT) + return handle_interrupt_window(vcpu); + else if (exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) + return handle_external_interrupt(vcpu); + else if (exit_reason == EXIT_REASON_HLT) + return kvm_emulate_halt(vcpu); + else if (exit_reason == EXIT_REASON_EPT_MISCONFIG) + return handle_ept_misconfig(vcpu); +#endif return kvm_vmx_exit_handlers[exit_reason](vcpu); - else { + } else { vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n", exit_reason); dump_vmcs(); -- 2.39.5