Re: [Xen-devel] [PATCH 4/5] libxc/pvh: set default MTRR type to write-back

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Mon, May 14, 2018 at 05:00:51PM +0100, Wei Liu wrote:
> On Thu, May 10, 2018 at 06:15:04PM +0100, Roger Pau Monne wrote:
> > @@ -1014,6 +1034,30 @@ static int vcpu_hvm(struct xc_dom_image *dom)
> >      if ( dom->start_info_seg.pfn )
> >          bsp_ctx.cpu.rbx = dom->start_info_seg.pfn << PAGE_SHIFT;
> >  
> > +    /* Set the MTRR. */
> > +    bsp_ctx.mtrr_d.typecode = HVM_SAVE_CODE(MTRR);
> > +    bsp_ctx.mtrr_d.instance = 0;
> > +    bsp_ctx.mtrr_d.length = HVM_SAVE_LENGTH(MTRR);
> > +
> > +    mtrr_record = hvm_get_save_record(full_ctx, HVM_SAVE_CODE(MTRR), 0);
> > +    if ( !mtrr_record )
> > +    {
> > +        xc_dom_panic(dom->xch, XC_INTERNAL_ERROR,
> > +                     "%s: unable to get MTRR save record", __func__);
> > +        goto out;
> > +    }
> 
> Will this break cross version migration when the older hypervisor
> doesn't have such record?

This migration record is already present, it's not introduced in this
patch series. I'm simply making use of it in order to set a valid
initial MTRR state.

Thanks, Roger.

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