Re: [Xen-devel] [PATCH 06/16] vmx: nest: handling VMX instruction exits

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 15:29 +0100 on 13 Sep (1284391777), Dong, Eddie wrote:
> Tim Deegan wrote:
> > At 08:05 +0100 on 10 Sep (1284105901), Dong, Eddie wrote:
> >> Qing He wrote:
> >>> +static int __clear_current_vvmcs(struct vmx_nest_struct *nest) +{
> >>> +    int rc;
> >>> +
> >>> +    if ( nest->svmcs )
> >>> +        __vmpclear(virt_to_maddr(nest->svmcs));
> >>> +
> >>> +#if !CONFIG_VVMCS_MAPPING
> >>> +    rc = hvm_copy_to_guest_phys(nest->gvmcs_pa, nest->vvmcs,
> >> 
> >> 
> >> Qing:
> >>    Why this may be failure? The only reason may be nest->gvmcs_pa, but
> >> I guess we already verified the address. 
> >> 
> > 
> > It was verified at load time, but the guest could have ballooned it
> > out in the meantime.
> 
> If the L1 guest allocated that GPA as VMCS memory, it can't balloon them out.
> If L1 is a mallicious guest and ballooned the VMCS memory out, it is worthy 
> to do. Not?
> 

Yes, in this case it looks like there's probably no harm in ignoring a
failure, but it seems reasonable to handle it.

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, XenServer Engineering
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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