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

[Christoph Egger <Christoph.Egger@xxxxxxx>]

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@xxxxxxxxx>
> Signed-off-by: Eddie Dong <eddie.dong@xxxxxxxxx>
>
> ---
>
> 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.

> +    /*
> +     * 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__ */
>
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