On Thu, Jan 14, 2021, Maxim Levitsky wrote:
> This allows it to be printed correctly by the trace print
It'd be helpful to explicitly say which tracepoint, and explain that the value
is read by vmx_get_exit_info(). It's far from obvious how this gets consumed.
> that follows.
>
Fixes: dcf068da7eb2 ("KVM: VMX: Introduce generic fastpath handler")
> Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
> ---
> arch/x86/kvm/vmx/vmx.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 2af05d3b05909..9b6e7dbf5e2bd 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -6771,6 +6771,8 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
> }
>
> vmx->exit_reason = vmcs_read32(VM_EXIT_REASON);
> + vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD);
Hrm, it probably makes sense to either do the VMREAD conditionally, or to
zero idt_vectoring_info in the vmx->fail path. I don't care about the cycles
on VM-Exit consistency checks, just that this would hide that the field is valid
if and only if VM-Enter fully succeeded. A third option would be to add a
comment saying that it's unnecessary if VM-Enter failed, but faster in the
common case to just do the VMREAD.
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 2af05d3b0590..3c172c05570a 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6774,13 +6774,15 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
if (unlikely((u16)vmx->exit_reason == EXIT_REASON_MCE_DURING_VMENTRY))
kvm_machine_check();
+ if (likely(!(vmx->exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY)))
+ vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD);
+
trace_kvm_exit(vmx->exit_reason, vcpu, KVM_ISA_VMX);
if (unlikely(vmx->exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY))
return EXIT_FASTPATH_NONE;
vmx->loaded_vmcs->launched = 1;
- vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD);
vmx_recover_nmi_blocking(vmx);
vmx_complete_interrupts(vmx);
> +
> if (unlikely((u16)vmx->exit_reason == EXIT_REASON_MCE_DURING_VMENTRY))
> kvm_machine_check();
>
> @@ -6780,7 +6782,6 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
> return EXIT_FASTPATH_NONE;
>
> vmx->loaded_vmcs->launched = 1;
> - vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD);
>
> vmx_recover_nmi_blocking(vmx);
> vmx_complete_interrupts(vmx);
> --
> 2.26.2
>
