From 0642391e2139a2c1b8a33f3fd816488d3f371d90 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 8 Jul 2020 21:51:55 +0200 Subject: x86/kvm/vmx: Add hardirq tracing to guest enter/exit Entering guest mode is more or less the same as returning to user space. From an instrumentation point of view both leave kernel mode and the transition to guest or user mode reenables interrupts on the host. In user mode an interrupt is served directly and in guest mode it causes a VM exit which then handles or reinjects the interrupt. The transition from guest mode or user mode to kernel mode disables interrupts, which needs to be recorded in instrumentation to set the correct state again. This is important for e.g. latency analysis because otherwise the execution time in guest or user mode would be wrongly accounted as interrupt disabled and could trigger false positives. Add hardirq tracing to guest enter/exit functions in the same way as it is done in the user mode enter/exit code, respecting the RCU requirements. Signed-off-by: Thomas Gleixner Reviewed-by: Alexandre Chartre Acked-by: Peter Zijlstra Acked-by: Paolo Bonzini Message-Id: <20200708195321.822002354@linutronix.de> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/vmx.c | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-) (limited to 'arch/x86/kvm/vmx') diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 4b4796d5123d..421cff3aa5b5 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6732,9 +6732,21 @@ reenter_guest: 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(). + * + * This ensures that e.g. latency analysis on the host observes + * guest mode as interrupt enabled. + * + * guest_enter_irqoff() informs context tracking about the + * transition to guest mode and if enabled adjusts RCU state + * accordingly. */ + 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)) @@ -6751,9 +6763,20 @@ reenter_guest: 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' as recorded before entering guest mode. + * Same as enter_from_user_mode(). + * + * guest_exit_irqoff() restores host context and reinstates RCU if + * enabled and required. + * + * 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_finish(); /* * We do not use IBRS in the kernel. If this vCPU has used the -- cgit v1.2.3