Re: [PATCH 08/16] vmx: nest: vmresume/vmlaunch

[Christoph Egger <Christoph.Egger@amd.com>]

On Wednesday 15 September 2010 11:52:26 Christoph Egger wrote:
> On Wednesday 08 September 2010 17:22:16 Qing He wrote:
> > vmresume and vmlaunch instructions and transitional states
> >
> > Signed-off-by: Qing He <qing.he@intel.com>
> > Signed-off-by: Eddie Dong <eddie.dong@intel.com>
> >
> > ---
> >
> > diff -r e828d55c10bb xen/arch/x86/hvm/vmx/nest.c
> > --- a/xen/arch/x86/hvm/vmx/nest.c	Wed Sep 08 21:42:10 2010 +0800
> > +++ b/xen/arch/x86/hvm/vmx/nest.c	Wed Sep 08 22:04:16 2010 +0800
> > @@ -633,3 +633,33 @@
> >      hvm_inject_exception(TRAP_invalid_op, 0, 0);
> >      return X86EMUL_EXCEPTION;
> >  }
> > +
> > +int vmx_nest_handle_vmresume(struct cpu_user_regs *regs)
> > +{
> > +    struct vcpu *v = current;
> > +    struct vmx_nest_struct *nest = &v->arch.hvm_vmx.nest;
> > +    int rc;
> > +
> > +    if ( unlikely(!nest->guest_vmxon_pa) )
> > +        goto invalid_op;
> > +
> > +    rc = vmx_inst_check_privilege(regs);
> > +    if ( rc != X86EMUL_OKAY )
> > +        return rc;
> > +
> > +    if ( nest->vmcs_valid == 1 )
> > +        nest->vmresume_pending = 1;
> > +    else
> > +        vmreturn(regs, VMFAIL_INVALID);
> > +
> > +    return X86EMUL_OKAY;
> > +
> > +invalid_op:
> > +    hvm_inject_exception(TRAP_invalid_op, 0, 0);
> > +    return X86EMUL_EXCEPTION;
> > +}
> > +
> > +int vmx_nest_handle_vmlaunch(struct cpu_user_regs *regs)
> > +{
> > +    return vmx_nest_handle_vmresume(regs);
> > +}
> > diff -r e828d55c10bb xen/arch/x86/hvm/vmx/vmx.c
> > --- a/xen/arch/x86/hvm/vmx/vmx.c	Wed Sep 08 21:42:10 2010 +0800
> > +++ b/xen/arch/x86/hvm/vmx/vmx.c	Wed Sep 08 22:04:16 2010 +0800
> > @@ -2321,6 +2321,11 @@
> >      /* Now enable interrupts so it's safe to take locks. */
> >      local_irq_enable();
> >
> > +    /* XXX: This looks ugly, but we need a mechanism to ensure
> > +     * any pending vmresume has really happened
> > +     */
> > +    v->arch.hvm_vmx.nest.vmresume_in_progress = 0;
> > +
> >      if ( unlikely(exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY) )
> >          return vmx_failed_vmentry(exit_reason, regs);
> >
> > @@ -2592,6 +2597,11 @@
> >          if ( vmx_nest_handle_vmclear(regs) == X86EMUL_OKAY )
> >              __update_guest_eip(inst_len);
> >          break;
> > +    case EXIT_REASON_VMLAUNCH:
> > +        inst_len = __get_instruction_length();
> > +        if ( vmx_nest_handle_vmlaunch(regs) == X86EMUL_OKAY )
> > +            __update_guest_eip(inst_len);
> > +        break;
> >      case EXIT_REASON_VMPTRLD:
> >          inst_len = __get_instruction_length();
> >          if ( vmx_nest_handle_vmptrld(regs) == X86EMUL_OKAY )
> > @@ -2607,6 +2617,11 @@
> >          if ( vmx_nest_handle_vmread(regs) == X86EMUL_OKAY )
> >              __update_guest_eip(inst_len);
> >          break;
> > +    case EXIT_REASON_VMRESUME:
> > +        inst_len = __get_instruction_length();
> > +        if ( vmx_nest_handle_vmresume(regs) == X86EMUL_OKAY )
> > +            __update_guest_eip(inst_len);
> > +        break;
> >      case EXIT_REASON_VMWRITE:
> >          inst_len = __get_instruction_length();
> >          if ( vmx_nest_handle_vmwrite(regs) == X86EMUL_OKAY )
> > @@ -2625,8 +2640,6 @@
> >
> >      case EXIT_REASON_MWAIT_INSTRUCTION:
> >      case EXIT_REASON_MONITOR_INSTRUCTION:
> > -    case EXIT_REASON_VMLAUNCH:
> > -    case EXIT_REASON_VMRESUME:
> >          vmx_inject_hw_exception(TRAP_invalid_op,
> > HVM_DELIVER_NO_ERROR_CODE); break;
> >
> > diff -r e828d55c10bb xen/include/asm-x86/hvm/vmx/nest.h
> > --- a/xen/include/asm-x86/hvm/vmx/nest.h	Wed Sep 08 21:42:10 2010 +0800
> > +++ b/xen/include/asm-x86/hvm/vmx/nest.h	Wed Sep 08 22:04:16 2010 +0800
> > @@ -40,6 +40,20 @@
> >      void                *vvmcs;
> >      struct vmcs_struct  *svmcs;
> >      int                  vmcs_valid;
> > +
> > +    /*
> > +     * vmexit_pending and vmresume_pending is to mark pending
> > +     * switches, they are cleared when physical vmcs is changed.
> > +     */
> > +    int                  vmexit_pending;
> > +    int                  vmresume_pending;
>
> This is functional equal to the vmentry flag in struct nestedhvm.

Is it possible to have both vmexit and vmresume pending at the same time ?

Christoph

>
> > +    /*
> > +     * upon L1->L2, there is a window between context switch and
> > +     * the physical vmentry of the shadow vmcs, protect against it
> > +     * with vmresume_in_progress
> > +     */
> > +    int                  vmresume_in_progress;
> >  };
>
> What is the window you describe in the comment ? And which problem
> does it arise?
>
> You use this to check if you can inject interrupts into the l2 guest.
> To merge the interrupt code as Tim said in
> http://lists.xensource.com/archives/html/xen-devel/2010-09/msg00747.html
> you can probably use the nh_gif field for this.
>
>
> Christoph
>
> >  int vmx_nest_handle_vmxon(struct cpu_user_regs *regs);
> > @@ -52,4 +66,7 @@
> >  int vmx_nest_handle_vmread(struct cpu_user_regs *regs);
> >  int vmx_nest_handle_vmwrite(struct cpu_user_regs *regs);
> >
> > +int vmx_nest_handle_vmresume(struct cpu_user_regs *regs);
> > +int vmx_nest_handle_vmlaunch(struct cpu_user_regs *regs);
> > +
> >  #endif /* __ASM_X86_HVM_NEST_H__ */
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@lists.xensource.com
> > http://lists.xensource.com/xen-devel



-- 
---to satisfy European Law for business letters:
Advanced Micro Devices GmbH
Einsteinring 24, 85609 Dornach b. Muenchen
Geschaeftsfuehrer: Alberto Bozzo, Andrew Bowd
Sitz: Dornach, Gemeinde Aschheim, Landkreis Muenchen
Registergericht Muenchen, HRB Nr. 43632