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

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, May 14, 2018 at 05:02:47PM +0100, Roger Pau Monné wrote:
> 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.
> 

Then I'm even more confused: does this mean the record is not properly
honoured in the hypervisor? I.e. this is a hypervisor bug?

Wei.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel