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SubjectRe: [patch V4 part 2 14/18] x86/kvm/vmx: Add hardirq tracing to guest enter/exit
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On 05/05/20 15:41, Thomas Gleixner wrote:
> 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@linutronix.de>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Sean Christopherson <sean.j.christopherson@intel.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
>

Acked-by: Paolo Bonzini <pbonzini@redhat.com>

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