Re: [Xen-devel] [PATCH v2 2/2] x86/hvm: Don't intercept #UD exceptions in general

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 27.01.16 at 20:13, <andrew.cooper3@xxxxxxxxxx> wrote:
> --- a/xen/arch/x86/hvm/svm/vmcb.c
> +++ b/xen/arch/x86/hvm/svm/vmcb.c
> @@ -192,6 +192,7 @@ static int construct_vmcb(struct vcpu *v)
>  
>      vmcb->_exception_intercepts =
>          HVM_TRAP_MASK
> +        | (opt_hvm_fep ? (1U << TRAP_invalid_op) : 0)
>          | (1U << TRAP_no_device);

This assumes a certain sequence of hypercalls by the tool stack
(i.e. set-cpuid only after all vCPU-s got created, or else the
intercept won't get enabled), which I think we should avoid.
Instead I think you'd better call the new hook from
hvm_vcpu_initialise().

Iif the above is not an option for some reason, and considering
you do the same change in vmcs.c, wouldn't it make sense to
extend HVM_TRAP_MASK accordingly?

Jan


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