Re: [Xen-devel] [PATCH] x86: Meltdown band-aid against malicious 64-bit PV guests

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Fri, 12 Jan 2018, Jan Beulich wrote:
> >>> On 12.01.18 at 18:02, <roger.pau@xxxxxxxxxx> wrote:
> > On Fri, Jan 12, 2018 at 03:19:38AM -0700, Jan Beulich wrote:
> >> @@ -799,6 +982,10 @@ void __init smp_prepare_cpus(unsigned in
> >>  
> >>      stack_base[0] = stack_start;
> >>  
> >> +    if ( !setup_cpu_root_pgt(0) )
> >> +        panic("No memory for root page table\n");
> >> +    get_cpu_info()->pv_cr3 = __pa(per_cpu(root_pgt, 0));
> > 
> > Wouldn't it be helpful to have a command line option to decide whether
> > to enable this feature or not?
> 
> Well, that would be an option, but falling into the optimization
> category. Once the basic concept has been proven by a 2nd
> party to have no obvious flaws, along with backporting some
> of the improvements would be my goal to work on, but the
> latter behind looking at the Spectre patches (i.e. I first want
> to get all fixes sorted, and then deal with improvements).

That's an amazing work, Jan. Thank you! Finally, a fix I can deploy. As
soon as this patch is properly verified, I think we should update all
references to Meltdown in our docs and advisories to point to this fix.

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