linux-kernel - [patch V4 part 2 14/18] x86/kvm/vmx: Add hardirq tracing to guest enter/exit

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Date:   Tue, 05 May 2020 15:41:26 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, "Paul E. McKenney" <paulmck@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>
Subject: [patch V4 part 2 14/18] x86/kvm/vmx: Add hardirq tracing to guest enter/exit

Add hardirq tracing to guest enter/exit functions in the same way as it
is done in the user mode enter/exit code.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/vmx/vmx.c |   25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6604,9 +6604,19 @@ static void vmx_vcpu_run(struct kvm_vcpu
 	x86_spec_ctrl_set_guest(vmx->spec_ctrl, 0);
 
 	/*
-	 * Tell context tracking that this CPU is about to enter guest mode.
+	 * VMENTER enables interrupts (host state), but the kernel state is
+	 * interrupts disabled when this is invoked. Also tell RCU about
+	 * it. This is the same logic as for exit_to_user_mode().
+	 *
+	 * 1) Trace interrupts on state
+	 * 2) Prepare lockdep with RCU on
+	 * 3) Invoke context tracking if enabled to adjust RCU state
+	 * 4) Tell lockdep that interrupts are enabled
 	 */
+	trace_hardirqs_on_prepare();
+	lockdep_hardirqs_on_prepare(CALLER_ADDR0);
 	guest_enter_irqoff();
+	lockdep_hardirqs_on(CALLER_ADDR0);
 
 	/* L1D Flush includes CPU buffer clear to mitigate MDS */
 	if (static_branch_unlikely(&vmx_l1d_should_flush))
@@ -6623,9 +6633,20 @@ static void vmx_vcpu_run(struct kvm_vcpu
 	vcpu->arch.cr2 = read_cr2();
 
 	/*
-	 * Tell context tracking that this CPU is back.
+	 * VMEXIT disables interrupts (host state), but tracing and lockdep
+	 * have them in state 'on'. Same as enter_from_user_mode().
+	 *
+	 * 1) Tell lockdep that interrupts are disabled
+	 * 2) Invoke context tracking if enabled to reactivate RCU
+	 * 3) Trace interrupts off state
+	 *
+	 * 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.
 	 */
+	lockdep_hardirqs_off(CALLER_ADDR0);
 	guest_exit_irqoff();
+	trace_hardirqs_off_prepare();
 
 	/*
 	 * We do not use IBRS in the kernel. If this vCPU has used the