Re: [Xen-devel] [PATCH RFC 03/12] xen/x86: allow the emulated APICs to be enbled for the hardware domain

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 29/07/16 17:28, Roger Pau Monne wrote:
>          if ( is_hardware_domain(d) )
> -            config->emulation_flags |= XEN_X86_EMU_PIT;
> -        if ( config->emulation_flags != 0 &&
> -             (config->emulation_flags !=
> -              (is_hvm_domain(d) ? XEN_X86_EMU_ALL : XEN_X86_EMU_PIT)) )
> +            emflags |= XEN_X86_EMU_PIT;
> +
> +        if ( (is_hardware_domain(d) ?
> +              (is_hvm_domain(d) && emflags !=
> +              (XEN_X86_EMU_PIT|XEN_X86_EMU_LAPIC|XEN_X86_EMU_IOAPIC)) :
> +              (emflags && (is_hvm_domain(d) ? (emflags != XEN_X86_EMU_ALL) :
> +                                              (emflags != 
> XEN_X86_EMU_PIT)))) )

This is getting very complicated.

It is rather important (security wise) and not a hotpath.  Could I
please request that you move this logic to a helper such as:

static bool emulation_flags_ok(const struct domain *d, uint32_t emflags)

and make this more readable.  Any decent compiler will inline and
simplify it appropriately.

~Andrew

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