Commit f7f39c50 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: x86: Exit to userspace if fastpath triggers one on instruction skip 

Exit to userspace if a fastpath handler triggers such an exit, which can
happen when skipping the instruction, e.g. due to userspace
single-stepping the guest via KVM_GUESTDBG_SINGLESTEP or because of an
emulation failure.

Fixes: 404d5d7b ("KVM: X86: Introduce more exit_fastpath_completion enum values")
Link: https://lore.kernel.org/r/20240802195120.325560-4-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent ea60229a

arch/x86/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -211,6 +211,7 @@ enum exit_fastpath_completion { 
	EXIT_FASTPATH_NONE,

	EXIT_FASTPATH_REENTER_GUEST,

	EXIT_FASTPATH_EXIT_HANDLED,

	EXIT_FASTPATH_EXIT_USERSPACE,

};

typedef enum exit_fastpath_completion fastpath_t;

arch/x86/kvm/x86.c

+7 −2
Original line number Diff line number Diff line
@@ -2206,7 +2206,9 @@ fastpath_t handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu) 
	}



	if (handled) {

		kvm_skip_emulated_instruction(vcpu);

		if (!kvm_skip_emulated_instruction(vcpu))

			ret = EXIT_FASTPATH_EXIT_USERSPACE;

		else

			ret = EXIT_FASTPATH_REENTER_GUEST;

		trace_kvm_msr_write(msr, data);

	} else {
@@ -11196,6 +11198,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) 
	if (vcpu->arch.apic_attention)

		kvm_lapic_sync_from_vapic(vcpu);



	if (unlikely(exit_fastpath == EXIT_FASTPATH_EXIT_USERSPACE))

		return 0;



	r = kvm_x86_call(handle_exit)(vcpu, exit_fastpath);

	return r;