RE: [PATCH v2 2/3] KVM:SVM: Add extended intercept support

[Babu Moger <babu.moger@amd.com>]

> -----Original Message-----
> From: Jim Mattson <jmattson@google.com>
> Sent: Tuesday, June 16, 2020 6:17 PM
> To: Moger, Babu <Babu.Moger@amd.com>
> Cc: Wanpeng Li <wanpengli@tencent.com>; Joerg Roedel <joro@8bytes.org>;
> the arch/x86 maintainers <x86@kernel.org>; Sean Christopherson
> <sean.j.christopherson@intel.com>; Ingo Molnar <mingo@redhat.com>;
> Borislav Petkov <bp@alien8.de>; H . Peter Anvin <hpa@zytor.com>; Paolo
> Bonzini <pbonzini@redhat.com>; Vitaly Kuznetsov <vkuznets@redhat.com>;
> Thomas Gleixner <tglx@linutronix.de>; LKML <linux-kernel@vger.kernel.org>;
> kvm list <kvm@vger.kernel.org>
> Subject: Re: [PATCH v2 2/3] KVM:SVM: Add extended intercept support
> 
> On Tue, Jun 16, 2020 at 3:03 PM Babu Moger <babu.moger@amd.com> wrote:
> >
> > The new intercept bits have been added in vmcb control
> > area to support the interception of INVPCID instruction.
> >
> > The following bit is added to the VMCB layout control area
> > to control intercept of INVPCID:
> >
> > Byte Offset     Bit(s)          Function
> > 14h             2               intercept INVPCID
> >
> > Add the interfaces to support these extended interception.
> > Also update the tracing for extended intercepts.
> >
> > AMD documentation for INVPCID feature is available at "AMD64
> > Architecture Programmer’s Manual Volume 2: System Programming,
> > Pub. 24593 Rev. 3.34(or later)"
> >
> > The documentation can be obtained at the links below:
> > Link:
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.a
> md.com%2Fsystem%2Ffiles%2FTechDocs%2F24593.pdf&amp;data=02%7C01%7
> Cbabu.moger%40amd.com%7C4cedcb3567194883601e08d8124b6be7%7C3dd8
> 961fe4884e608e11a82d994e183d%7C0%7C0%7C637279463210520563&amp;s
> data=oRQq0hj0O43A4lnl8JEb%2BHt8oCFHWxcqvLaA1%2BacTJc%3D&amp;reser
> ved=0
> > Link:
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.
> kernel.org%2Fshow_bug.cgi%3Fid%3D206537&amp;data=02%7C01%7Cbabu.m
> oger%40amd.com%7C4cedcb3567194883601e08d8124b6be7%7C3dd8961fe48
> 84e608e11a82d994e183d%7C0%7C0%7C637279463210520563&amp;sdata=EtA
> rCUBB8etloN%2B%2Blx42RZqai12QFvtJefnxBn1ryMQ%3D&amp;reserved=0
> 
> Not your change, but this documentation is terrible. There is no
> INVLPCID instruction, nor is there a PCID instruction.

Sorry about that. I will bring this to their notice.

> 
> > Signed-off-by: Babu Moger <babu.moger@amd.com>
> > ---
> >  arch/x86/include/asm/svm.h |    3 ++-
> >  arch/x86/kvm/svm/nested.c  |    6 +++++-
> >  arch/x86/kvm/svm/svm.c     |    1 +
> >  arch/x86/kvm/svm/svm.h     |   18 ++++++++++++++++++
> >  arch/x86/kvm/trace.h       |   12 ++++++++----
> >  5 files changed, 34 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
> > index 8a1f5382a4ea..62649fba8908 100644
> > --- a/arch/x86/include/asm/svm.h
> > +++ b/arch/x86/include/asm/svm.h
> > @@ -61,7 +61,8 @@ struct __attribute__ ((__packed__)) vmcb_control_area {
> >         u32 intercept_dr;
> >         u32 intercept_exceptions;
> >         u64 intercept;
> > -       u8 reserved_1[40];
> > +       u32 intercept_extended;
> > +       u8 reserved_1[36];
> 
> It seems like a more straightforward implementation would simply
> change 'u64 intercept' to 'u32 intercept[3].'

Sure. Will change it.

> 
> >         u16 pause_filter_thresh;
> >         u16 pause_filter_count;
> >         u64 iopm_base_pa;
> > diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> > index 8a6db11dcb43..7f6d0f2533e2 100644
> > --- a/arch/x86/kvm/svm/nested.c
> > +++ b/arch/x86/kvm/svm/nested.c
> > @@ -121,6 +121,7 @@ void recalc_intercepts(struct vcpu_svm *svm)
> >         c->intercept_dr = h->intercept_dr;
> >         c->intercept_exceptions = h->intercept_exceptions;
> >         c->intercept = h->intercept;
> > +       c->intercept_extended = h->intercept_extended;
> >
> >         if (g->int_ctl & V_INTR_MASKING_MASK) {
> >                 /* We only want the cr8 intercept bits of L1 */
> > @@ -142,6 +143,7 @@ void recalc_intercepts(struct vcpu_svm *svm)
> >         c->intercept_dr |= g->intercept_dr;
> >         c->intercept_exceptions |= g->intercept_exceptions;
> >         c->intercept |= g->intercept;
> > +       c->intercept_extended |= g->intercept_extended;
> >  }
> >
> >  static void copy_vmcb_control_area(struct vmcb_control_area *dst,
> > @@ -151,6 +153,7 @@ static void copy_vmcb_control_area(struct
> vmcb_control_area *dst,
> >         dst->intercept_dr         = from->intercept_dr;
> >         dst->intercept_exceptions = from->intercept_exceptions;
> >         dst->intercept            = from->intercept;
> > +       dst->intercept_extended   = from->intercept_extended;
> >         dst->iopm_base_pa         = from->iopm_base_pa;
> >         dst->msrpm_base_pa        = from->msrpm_base_pa;
> >         dst->tsc_offset           = from->tsc_offset;
> > @@ -433,7 +436,8 @@ int nested_svm_vmrun(struct vcpu_svm *svm)
> >         trace_kvm_nested_intercepts(nested_vmcb->control.intercept_cr &
> 0xffff,
> >                                     nested_vmcb->control.intercept_cr >> 16,
> >                                     nested_vmcb->control.intercept_exceptions,
> > -                                   nested_vmcb->control.intercept);
> > +                                   nested_vmcb->control.intercept,
> > +                                   nested_vmcb->control.intercept_extended);
> >
> >         /* Clear internal status */
> >         kvm_clear_exception_queue(&svm->vcpu);
> > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> > index 9e333b91ff78..285e5e1ff518 100644
> > --- a/arch/x86/kvm/svm/svm.c
> > +++ b/arch/x86/kvm/svm/svm.c
> > @@ -2801,6 +2801,7 @@ static void dump_vmcb(struct kvm_vcpu *vcpu)
> >         pr_err("%-20s%04x\n", "dr_write:", control->intercept_dr >> 16);
> >         pr_err("%-20s%08x\n", "exceptions:", control->intercept_exceptions);
> >         pr_err("%-20s%016llx\n", "intercepts:", control->intercept);
> > +       pr_err("%-20s%08x\n", "intercepts (extended):", control-
> >intercept_extended);
> >         pr_err("%-20s%d\n", "pause filter count:", control->pause_filter_count);
> >         pr_err("%-20s%d\n", "pause filter threshold:",
> >                control->pause_filter_thresh);
> > diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> > index 6ac4c00a5d82..935d08fac03d 100644
> > --- a/arch/x86/kvm/svm/svm.h
> > +++ b/arch/x86/kvm/svm/svm.h
> > @@ -311,6 +311,24 @@ static inline void clr_intercept(struct vcpu_svm *svm,
> int bit)
> >         recalc_intercepts(svm);
> >  }
> >
> > +static inline void set_extended_intercept(struct vcpu_svm *svm, int bit)
> > +{
> > +       struct vmcb *vmcb = get_host_vmcb(svm);
> > +
> > +       vmcb->control.intercept_extended |= (1U << bit);
> > +
> > +       recalc_intercepts(svm);
> > +}
> > +
> > +static inline void clr_extended_intercept(struct vcpu_svm *svm, int bit)
> > +{
> > +       struct vmcb *vmcb = get_host_vmcb(svm);
> > +
> > +       vmcb->control.intercept_extended &= ~(1U << bit);
> > +
> > +       recalc_intercepts(svm);
> > +}
> 
> You wouldn't need these new functions if you defined 'u32
> intercept[3],' as I suggested above. Just change set_intercept and
> clr_intercept to use __set_bit and __clear_bit.

Yes. Will change it. Thanks

> 
> >  static inline bool is_intercept(struct vcpu_svm *svm, int bit)
> >  {
> >         return (svm->vmcb->control.intercept & (1ULL << bit)) != 0;
> > diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
> > index b66432b015d2..5c841c42b33d 100644
> > --- a/arch/x86/kvm/trace.h
> > +++ b/arch/x86/kvm/trace.h
> > @@ -544,14 +544,16 @@ TRACE_EVENT(kvm_nested_vmrun,
> >  );
> >
> >  TRACE_EVENT(kvm_nested_intercepts,
> > -           TP_PROTO(__u16 cr_read, __u16 cr_write, __u32 exceptions, __u64
> intercept),
> > -           TP_ARGS(cr_read, cr_write, exceptions, intercept),
> > +           TP_PROTO(__u16 cr_read, __u16 cr_write, __u32 exceptions, __u64
> intercept,
> > +                    __u32 extended),
> > +           TP_ARGS(cr_read, cr_write, exceptions, intercept, extended),
> >
> >         TP_STRUCT__entry(
> >                 __field(        __u16,          cr_read         )
> >                 __field(        __u16,          cr_write        )
> >                 __field(        __u32,          exceptions      )
> >                 __field(        __u64,          intercept       )
> > +               __field(        __u32,          extended        )
> >         ),
> >
> >         TP_fast_assign(
> > @@ -559,11 +561,13 @@ TRACE_EVENT(kvm_nested_intercepts,
> >                 __entry->cr_write       = cr_write;
> >                 __entry->exceptions     = exceptions;
> >                 __entry->intercept      = intercept;
> > +               __entry->extended       = extended;
> >         ),
> >
> > -       TP_printk("cr_read: %04x cr_write: %04x excp: %08x intercept: %016llx",
> > +       TP_printk("cr_read: %04x cr_write: %04x excp: %08x intercept: %016llx"
> > +                 "intercept (extended): %08x",
> >                 __entry->cr_read, __entry->cr_write, __entry->exceptions,
> > -               __entry->intercept)
> > +               __entry->intercept, __entry->extended)
> >  );
> >  /*
> >   * Tracepoint for #VMEXIT while nested
> >