Commit 87fa7f3e authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Paolo Bonzini
Browse files

x86/kvm: Move context tracking where it belongs 



Context tracking for KVM happens way too early in the vcpu_run()
code. Anything after guest_enter_irqoff() and before guest_exit_irqoff()
cannot use RCU and should also be not instrumented.

The current way of doing this covers way too much code. Move it closer to
the actual vmenter/exit code.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarAlexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Acked-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <20200708195321.724574345@linutronix.de>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 841c2be0

arch/x86/kvm/svm/svm.c

+16 −0
Original line number Diff line number Diff line
@@ -3398,6 +3398,14 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu) 
	 */

	x86_spec_ctrl_set_guest(svm->spec_ctrl, svm->virt_spec_ctrl);



	/*

	 * Tell context tracking that this CPU is about to enter guest

	 * mode. This has to be after x86_spec_ctrl_set_guest() because

	 * that can take locks (lockdep needs RCU) and calls into world and

	 * some more.

	 */

	guest_enter_irqoff();



	__svm_vcpu_run(svm->vmcb_pa, (unsigned long *)&svm->vcpu.arch.regs);



#ifdef CONFIG_X86_64
@@ -3408,6 +3416,14 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu) 
	loadsegment(gs, svm->host.gs);

#endif

#endif

	/*

	 * Tell context tracking that this CPU is back.

	 *

	 * This needs to be done before the below as native_read_msr()

	 * contains a tracepoint and x86_spec_ctrl_restore_host() calls

	 * into world and some more.

	 */

	guest_exit_irqoff();



	/*

	 * We do not use IBRS in the kernel. If this vCPU has used the

arch/x86/kvm/vmx/vmx.c

+10 −0
Original line number Diff line number Diff line
@@ -6731,6 +6731,11 @@ reenter_guest: 
	 */

	x86_spec_ctrl_set_guest(vmx->spec_ctrl, 0);



	/*

	 * Tell context tracking that this CPU is about to enter guest mode.

	 */

	guest_enter_irqoff();



	/* L1D Flush includes CPU buffer clear to mitigate MDS */

	if (static_branch_unlikely(&vmx_l1d_should_flush))

		vmx_l1d_flush(vcpu);
@@ -6745,6 +6750,11 @@ reenter_guest: 


	vcpu->arch.cr2 = read_cr2();



	/*

	 * Tell context tracking that this CPU is back.

	 */

	guest_exit_irqoff();



	/*

	 * We do not use IBRS in the kernel. If this vCPU has used the

	 * SPEC_CTRL MSR it may have left it on; save the value and

arch/x86/kvm/x86.c

+0 −2
Original line number Diff line number Diff line
@@ -8522,7 +8522,6 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) 
	}



	trace_kvm_entry(vcpu->vcpu_id);

	guest_enter_irqoff();



	fpregs_assert_state_consistent();

	if (test_thread_flag(TIF_NEED_FPU_LOAD))
@@ -8585,7 +8584,6 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) 
	local_irq_disable();

	kvm_after_interrupt(vcpu);



	guest_exit_irqoff();

	if (lapic_in_kernel(vcpu)) {

		s64 delta = vcpu->arch.apic->lapic_timer.advance_expire_delta;

		if (delta != S64_MIN) {

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