Re: [PATCH] KVM: stats: x86: vmx: add exit reason stats to vt-x instructions

[Jing Zhang <jingzhangos@google.com>]

Hi David,

On Thu, Aug 19, 2021 at 11:43 AM David Matlack <dmatlack@google.com> wrote:
>
> On Thu, Aug 19, 2021 at 11:00 AM Jing Zhang <jingzhangos@google.com> wrote:
> >
> > These stats will be used to monitor the nested virtualization use in
> > VMs. Most importantly: VMXON exits are evidence that the guest has
> > enabled VMX, VMLAUNCH/VMRESUME exits are evidence that the guest has run
> > an L2.
>
> This series is superseded by Peter Feiner's internal KVM patch that
> exports an array of counts, one for each VM-exit reason ("kvm: vmx
> exit reason stats"). This is better since it does not require
> instrumenting every VM-exit handler in KVM and introducing a stat for
> every exit.
>
> Assuming upstream would want exit count stats I would suggest we drop
> this patch and upstream Peter's instead. Although we need to sort out
> AMD and other architectures as well.
>
Sure, will drop this.

Thanks,
Jing
> >
> > Original-by: David Matlack <dmatlack@google.com>
> > Signed-off-by: Jing Zhang <jingzhangos@google.com>
> > ---
> >  arch/x86/include/asm/kvm_host.h | 11 +++++++++++
> >  arch/x86/kvm/vmx/nested.c       | 17 +++++++++++++++++
> >  arch/x86/kvm/x86.c              | 13 ++++++++++++-
> >  3 files changed, 40 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index 09b256db394a..e3afbc7926e0 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -1257,6 +1257,17 @@ struct kvm_vcpu_stat {
> >         u64 directed_yield_attempted;
> >         u64 directed_yield_successful;
> >         u64 guest_mode;
> > +       u64 vmclear_exits;
> > +       u64 vmlaunch_exits;
> > +       u64 vmptrld_exits;
> > +       u64 vmptrst_exits;
> > +       u64 vmread_exits;
> > +       u64 vmresume_exits;
> > +       u64 vmwrite_exits;
> > +       u64 vmoff_exits;
> > +       u64 vmon_exits;
> > +       u64 invept_exits;
> > +       u64 invvpid_exits;
> >  };
> >
> >  struct x86_instruction_info;
> > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> > index bc6327950657..8696f2612953 100644
> > --- a/arch/x86/kvm/vmx/nested.c
> > +++ b/arch/x86/kvm/vmx/nested.c
> > @@ -4879,6 +4879,7 @@ static int handle_vmon(struct kvm_vcpu *vcpu)
> >         const u64 VMXON_NEEDED_FEATURES = FEAT_CTL_LOCKED
> >                 | FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX;
> >
> > +       ++vcpu->stat.vmon_exits;
> >         /*
> >          * The Intel VMX Instruction Reference lists a bunch of bits that are
> >          * prerequisite to running VMXON, most notably cr4.VMXE must be set to
> > @@ -4964,6 +4965,7 @@ static inline void nested_release_vmcs12(struct kvm_vcpu *vcpu)
> >  /* Emulate the VMXOFF instruction */
> >  static int handle_vmoff(struct kvm_vcpu *vcpu)
> >  {
> > +       ++vcpu->stat.vmoff_exits;
> >         if (!nested_vmx_check_permission(vcpu))
> >                 return 1;
> >
> > @@ -4984,6 +4986,7 @@ static int handle_vmclear(struct kvm_vcpu *vcpu)
> >         u64 evmcs_gpa;
> >         int r;
> >
> > +       ++vcpu->stat.vmclear_exits;
> >         if (!nested_vmx_check_permission(vcpu))
> >                 return 1;
> >
> > @@ -5025,6 +5028,7 @@ static int handle_vmclear(struct kvm_vcpu *vcpu)
> >  /* Emulate the VMLAUNCH instruction */
> >  static int handle_vmlaunch(struct kvm_vcpu *vcpu)
> >  {
> > +       ++vcpu->stat.vmlaunch_exits;
> >         return nested_vmx_run(vcpu, true);
> >  }
> >
> > @@ -5032,6 +5036,7 @@ static int handle_vmlaunch(struct kvm_vcpu *vcpu)
> >  static int handle_vmresume(struct kvm_vcpu *vcpu)
> >  {
> >
> > +       ++vcpu->stat.vmresume_exits;
> >         return nested_vmx_run(vcpu, false);
> >  }
> >
> > @@ -5049,6 +5054,8 @@ static int handle_vmread(struct kvm_vcpu *vcpu)
> >         short offset;
> >         int len, r;
> >
> > +       ++vcpu->stat.vmread_exits;
> > +
> >         if (!nested_vmx_check_permission(vcpu))
> >                 return 1;
> >
> > @@ -5141,6 +5148,8 @@ static int handle_vmwrite(struct kvm_vcpu *vcpu)
> >          */
> >         u64 value = 0;
> >
> > +       ++vcpu->stat.vmwrite_exits;
> > +
> >         if (!nested_vmx_check_permission(vcpu))
> >                 return 1;
> >
> > @@ -5245,6 +5254,8 @@ static int handle_vmptrld(struct kvm_vcpu *vcpu)
> >         gpa_t vmptr;
> >         int r;
> >
> > +       ++vcpu->stat.vmptrld_exits;
> > +
> >         if (!nested_vmx_check_permission(vcpu))
> >                 return 1;
> >
> > @@ -5311,6 +5322,8 @@ static int handle_vmptrst(struct kvm_vcpu *vcpu)
> >         gva_t gva;
> >         int r;
> >
> > +       ++vcpu->stat.vmptrst_exits;
> > +
> >         if (!nested_vmx_check_permission(vcpu))
> >                 return 1;
> >
> > @@ -5351,6 +5364,8 @@ static int handle_invept(struct kvm_vcpu *vcpu)
> >         } operand;
> >         int i, r;
> >
> > +       ++vcpu->stat.invept_exits;
> > +
> >         if (!(vmx->nested.msrs.secondary_ctls_high &
> >               SECONDARY_EXEC_ENABLE_EPT) ||
> >             !(vmx->nested.msrs.ept_caps & VMX_EPT_INVEPT_BIT)) {
> > @@ -5431,6 +5446,8 @@ static int handle_invvpid(struct kvm_vcpu *vcpu)
> >         u16 vpid02;
> >         int r;
> >
> > +       ++vcpu->stat.invvpid_exits;
> > +
> >         if (!(vmx->nested.msrs.secondary_ctls_high &
> >               SECONDARY_EXEC_ENABLE_VPID) ||
> >                         !(vmx->nested.msrs.vpid_caps & VMX_VPID_INVVPID_BIT)) {
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 1a00af1b076b..c2c95b4c1a68 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -277,7 +277,18 @@ const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
> >         STATS_DESC_COUNTER(VCPU, nested_run),
> >         STATS_DESC_COUNTER(VCPU, directed_yield_attempted),
> >         STATS_DESC_COUNTER(VCPU, directed_yield_successful),
> > -       STATS_DESC_ICOUNTER(VCPU, guest_mode)
> > +       STATS_DESC_ICOUNTER(VCPU, guest_mode),
> > +       STATS_DESC_COUNTER(VCPU, vmclear_exits),
> > +       STATS_DESC_COUNTER(VCPU, vmlaunch_exits),
> > +       STATS_DESC_COUNTER(VCPU, vmptrld_exits),
> > +       STATS_DESC_COUNTER(VCPU, vmptrst_exits),
> > +       STATS_DESC_COUNTER(VCPU, vmread_exits),
> > +       STATS_DESC_COUNTER(VCPU, vmresume_exits),
> > +       STATS_DESC_COUNTER(VCPU, vmwrite_exits),
> > +       STATS_DESC_COUNTER(VCPU, vmoff_exits),
> > +       STATS_DESC_COUNTER(VCPU, vmon_exits),
> > +       STATS_DESC_COUNTER(VCPU, invept_exits),
> > +       STATS_DESC_COUNTER(VCPU, invvpid_exits),
> >  };
> >
> >  const struct kvm_stats_header kvm_vcpu_stats_header = {
> >
> > base-commit: 47e7414d53fc12407b7a43bba412ecbf54c84f82
> > --
> > 2.33.0.rc2.250.ged5fa647cd-goog
> >