linux-kernel - [patch V4 part 2 18/18] x86/kvm/svm: Move guest enter/exit into .noinstr.text

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Date:   Tue, 05 May 2020 15:41:30 +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 18/18] x86/kvm/svm: Move guest enter/exit into .noinstr.text

Move the functions which are inside the RCU off region into the
non-instrumentable text section.

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/svm/svm.c     |  102 ++++++++++++++++++++++++---------------------
 arch/x86/kvm/svm/vmenter.S |    2 
 2 files changed, 57 insertions(+), 47 deletions(-)

--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3278,6 +3278,61 @@ static void svm_cancel_injection(struct
 
 void __svm_vcpu_run(unsigned long vmcb_pa, unsigned long *regs);
 
+static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu,
+					struct vcpu_svm *svm)
+{
+	/*
+	 * 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
+	 *
+	 * 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.
+	 */
+	instr_begin();
+	trace_hardirqs_on_prepare();
+	lockdep_hardirqs_on_prepare(CALLER_ADDR0);
+	instr_end();
+	guest_enter_irqoff();
+	lockdep_hardirqs_on(CALLER_ADDR0);
+
+	__svm_vcpu_run(svm->vmcb_pa, (unsigned long *)&svm->vcpu.arch.regs);
+
+#ifdef CONFIG_X86_64
+	native_wrmsrl(MSR_GS_BASE, svm->host.gs_base);
+#else
+	loadsegment(fs, svm->host.fs);
+#ifndef CONFIG_X86_32_LAZY_GS
+	loadsegment(gs, svm->host.gs);
+#endif
+#endif
+
+	/*
+	 * VMEXIT disables interrupts (host state, see the CLI in the ASM
+	 * above), 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();
+	instr_begin();
+	trace_hardirqs_off_prepare();
+	instr_end();
+}
+
 static void svm_vcpu_run(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
@@ -3330,52 +3385,7 @@ static void svm_vcpu_run(struct kvm_vcpu
 	 */
 	x86_spec_ctrl_set_guest(svm->spec_ctrl, svm->virt_spec_ctrl);
 
-	/*
-	 * 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
-	 *
-	 * 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.
-	 */
-	trace_hardirqs_on_prepare();
-	lockdep_hardirqs_on_prepare(CALLER_ADDR0);
-	guest_enter_irqoff();
-	lockdep_hardirqs_on(CALLER_ADDR0);
-
-	__svm_vcpu_run(svm->vmcb_pa, (unsigned long *)&svm->vcpu.arch.regs);
-
-#ifdef CONFIG_X86_64
-	wrmsrl(MSR_GS_BASE, svm->host.gs_base);
-#else
-	loadsegment(fs, svm->host.fs);
-#ifndef CONFIG_X86_32_LAZY_GS
-	loadsegment(gs, svm->host.gs);
-#endif
-#endif
-
-	/*
-	 * VMEXIT disables interrupts (host state, see the CLI in the ASM
-	 * above), 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();
+	svm_vcpu_enter_exit(vcpu, svm);
 
 	/*
 	 * We do not use IBRS in the kernel. If this vCPU has used the
--- a/arch/x86/kvm/svm/vmenter.S
+++ b/arch/x86/kvm/svm/vmenter.S
@@ -27,7 +27,7 @@
 #define VCPU_R15	__VCPU_REGS_R15 * WORD_SIZE
 #endif
 
-	.text
+.section .noinstr.text, "ax"
 
 /**
  * __svm_vcpu_run - Run a vCPU via a transition to SVM guest mode