On Mon, Jan 18, 2021 at 04:28:26PM +1300, Kai Huang wrote: > From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> > > Convert vcpu_vmx.exit_reason from a u32 to a union (of size u32). The > full VM_EXIT_REASON field is comprised of a 16-bit basic exit reason in > bits 15:0, and single-bit modifiers in bits 31:16. > > Historically, KVM has only had to worry about handling the "failed > VM-Entry" modifier, which could only be set in very specific flows and > required dedicated handling. I.e. manually stripping the FAILED_VMENTRY > bit was a somewhat viable approach. But even with only a single bit to > worry about, KVM has had several bugs related to comparing a basic exit > reason against the full exit reason store in vcpu_vmx. > > Upcoming Intel features, e.g. SGX, will add new modifier bits that can > be set on more or less any VM-Exit, as opposed to the significantly more > restricted FAILED_VMENTRY, i.e. correctly handling everything in one-off > flows isn't scalable. Tracking exit reason in a union forces code to > explicitly choose between consuming the full exit reason and the basic > exit, and is a convenient way to document and access the modifiers. > > No functional change intended. > > Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> > Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx> > --- > arch/x86/kvm/vmx/nested.c | 42 +++++++++++++++--------- > arch/x86/kvm/vmx/vmx.c | 68 ++++++++++++++++++++------------------- > arch/x86/kvm/vmx/vmx.h | 25 +++++++++++++- > 3 files changed, 86 insertions(+), 49 deletions(-) > > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c > index 0fbb46990dfc..f112c2482887 100644 > --- a/arch/x86/kvm/vmx/nested.c > +++ b/arch/x86/kvm/vmx/nested.c > @@ -3311,7 +3311,11 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, > struct vmcs12 *vmcs12 = get_vmcs12(vcpu); > enum vm_entry_failure_code entry_failure_code; > bool evaluate_pending_interrupts; > - u32 exit_reason, failed_index; > + u32 failed_index; > + union vmx_exit_reason exit_reason = { > + .basic = -1, > + .failed_vmentry = 1, > + }; Instead, put this declaration to the correct place, following the reverse christmas tree ordering: union vmx_exit_reason exit_reason = {}; And after declarations: exit_reason.basic = -1; exit_reason.failed_vmentry = 1; More pleasing for the eye. /Jarkko