Re: [Xen-devel] [PATCH 1/6] x86/cpuid: Hide VT-x/SVM from HVM-based control domains

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

On Tue, Jan 24, 2017 at 08:10:56AM -0700, Jan Beulich wrote:
> >>> On 24.01.17 at 15:38, <roger.pau@xxxxxxxxxx> wrote:
> > On Wed, Jan 18, 2017 at 07:40:53PM +0000, Andrew Cooper wrote:
> >> The VT-x/SVM features are hidden from PV dom0 by the pv_featureset[] upper
> >> mask, but nothing thusfar has prevented the features being visible in
> >> HVM-based control domains (where there is no toolstack decision to hide the
> >> features).
> >> 
> >> As a side effect of calling nestedhvm_enabled() earlier during domain
> >> creation, it needs to cope with the params[] array array not having been
> >> allocated.
> >> 
> >> Reported-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> >> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> >> ---
> >> CC: Jan Beulich <JBeulich@xxxxxxxx>
> >> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> >> ---
> >>  xen/arch/x86/cpuid.c         | 25 ++++++++++++++++++-------
> >>  xen/arch/x86/hvm/nestedhvm.c |  3 ++-
> >>  2 files changed, 20 insertions(+), 8 deletions(-)
> >> 
> >> diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
> >> index eb829d7..7b9af1b 100644
> >> --- a/xen/arch/x86/cpuid.c
> >> +++ b/xen/arch/x86/cpuid.c
> >> @@ -3,6 +3,7 @@
> >>  #include <xen/sched.h>
> >>  #include <asm/cpuid.h>
> >>  #include <asm/hvm/hvm.h>
> >> +#include <asm/hvm/nestedhvm.h>
> >>  #include <asm/hvm/vmx/vmcs.h>
> >>  #include <asm/processor.h>
> >>  #include <asm/xstate.h>
> >> @@ -361,14 +362,24 @@ void recalculate_cpuid_policy(struct domain *d)
> >>      cpuid_policy_to_featureset(p, fs);
> >>      cpuid_policy_to_featureset(max, max_fs);
> >>  
> >> -    /*
> >> -     * HVM domains using Shadow paging have further restrictions on their
> >> -     * available paging features.
> >> -     */
> >> -    if ( is_hvm_domain(d) && !hap_enabled(d) )
> >> +    if ( is_hvm_domain(d) )
> > 
> > This should be has_hvm_container_domain or else classic PVH is broken, but I
> > don't know how much we care about classic PVH any longer.
> 
> The old check excluded PVHv1 (due to it depending on HAP), as
> does the new check (in a more explicit way), so I don't see what's
> wrong here.

Right, I guess this is caused by e94ce5, which did:

     case EXIT_REASON_CPUID:
     {
-        int rc;
-
-        if ( is_pvh_vcpu(v) )
-        {
-            pv_cpuid(regs);
-            rc = 0;
-        }
-        else
-            rc = vmx_do_cpuid(regs);
+        int rc = vmx_do_cpuid(regs);

Which removed the special casing for the PVH CPUID, and I assume pv_cpuid used
to remove the VT-x extensions from the output of CPUID?

Roger.

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