Re: [PATCHv1 4/5] x86/viridian: set x87 FIP width to 4 for Windows guests

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 18/02/16 18:52, David Vrabel wrote:
> diff --git a/xen/arch/x86/hvm/viridian.c b/xen/arch/x86/hvm/viridian.c
> index 6bd844b..fb9f044 100644
> --- a/xen/arch/x86/hvm/viridian.c
> +++ b/xen/arch/x86/hvm/viridian.c
> @@ -148,6 +148,30 @@ static void dump_guest_os_id(const struct domain *d)
>             goi->fields.service_pack, goi->fields.build_number);
>  }
>  
> +static void set_guest_os_id(struct domain *d, uint64_t val)
> +{
> +    const union viridian_guest_os_id *goi;
> +
> +    d->arch.hvm_domain.viridian.guest_os_id.raw = val;
> +    goi = &d->arch.hvm_domain.viridian.guest_os_id;
> +
> +    /*
> +     * Microsoft Windows only saves the lower 32-bits of FIP/FDP and
> +     * can get upset if the selectors are not saved/restored by the
> +     * hypervisor.
> +     *
> +     * Only do this if the FIP width is not in auto-mode, so this
> +     * heuristic can be overriden by the toolstack.
> +     */
> +    if ( !d->arch.x87_fip_width )
> +    {
> +        if ( goi->fields.vendor == 1 && goi->fields.os == 4 )

Are there any named parameters we could use here?

In principle, Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
(allowing for the potential change of x86_fip_width per the discussion
on patch 3).

> +            d->arch.x87_fip_width = 4;
> +    }
> +
> +    dump_guest_os_id(d);
> +}
> +
>  static void dump_hypercall(const struct domain *d)
>  {
>      const union viridian_hypercall_gpa *hg;