Re: [Xen-devel] [PATCH RESEND v1 2/7] x86: configure vmcs for Intel processor trace virtualization

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.01.18 at 19:12, <luwei.kang@xxxxxxxxx> wrote:
> This patch configure VMCS to make Intel PT output address can be
> treat as guest physical address and translated by EPT when
> intel_pt option is true.
> There have some constraint condition on VMCS configuration,
> otherwise will cause VM entry failed.
> 
> 1. If the “Guest PT uses Guest Physical Addresses” execution
>    control is 1, the “Clear IA32_RTIT_CTL on exit” exit
>    control and the “Load IA32_RTIT_CTL on entry” entry
>    control must also be 1.
> 2. If the “Guest PT uses Guest Physical Addresses” execution
>    control is 1, the "enable EPT" execution control must
>    also be 1.

What are the implications for a guest running with hap=0?

> @@ -383,13 +388,28 @@ static int vmx_init_vmcs_config(void)
>          _vmx_secondary_exec_control &= 
> ~SECONDARY_EXEC_ENABLE_VIRT_EXCEPTIONS;
>  
>      min = 0;
> -    opt = VM_ENTRY_LOAD_GUEST_PAT | VM_ENTRY_LOAD_BNDCFGS;
> +    opt = VM_ENTRY_LOAD_GUEST_PAT | VM_ENTRY_LOAD_BNDCFGS |
> +          VM_ENTRY_CONCEAL_PT_PIP | VM_ENTRY_LOAD_IA32_RTIT_CTL;
>      _vmx_vmentry_control = adjust_vmx_controls(
>          "VMEntry Control", min, opt, MSR_IA32_VMX_ENTRY_CTLS, &mismatch);
>  
>      if ( mismatch )
>          return -EINVAL;
>  
> +    if ( !(_vmx_secondary_exec_control & SECONDARY_EXEC_ENABLE_EPT) ||
> +         !(_vmx_secondary_exec_control & SECONDARY_EXEC_PT_USE_GPA) ||
> +         !(_vmx_vmexit_control & VM_EXIT_CLEAR_IA32_RTIT_CTL) ||
> +         !(_vmx_vmentry_control & VM_ENTRY_LOAD_IA32_RTIT_CTL) )
> +    {
> +        _vmx_secondary_exec_control &= ~(SECONDARY_EXEC_PT_USE_GPA |
> +                                         SECONDARY_EXEC_CONCEAL_PT_PIP);
> +        _vmx_vmexit_control &= ~(VM_EXIT_CONCEAL_PT_PIP |
> +                                 VM_EXIT_CLEAR_IA32_RTIT_CTL);
> +        _vmx_vmentry_control &= ~(VM_ENTRY_CONCEAL_PT_PIP |
> +                                  VM_ENTRY_LOAD_IA32_RTIT_CTL);
> +        opt_intel_pt = 0;
> +    }

Besides clearing the flag here, shouldn't you also check it further up?

Jan


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