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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

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) )
     {
-        for ( i = 0; i < ARRAY_SIZE(max_fs); i++ )
-            max_fs[i] &= hvm_shadow_featuremask[i];
+        /*
+         * HVM domains using Shadow paging have further restrictions on their
+         * available paging features.
+         */
+        if ( !hap_enabled(d) )
+        {
+            for ( i = 0; i < ARRAY_SIZE(max_fs); i++ )
+                max_fs[i] &= hvm_shadow_featuremask[i];
+        }
+
+        /* Hide nested-virt if it hasn't been explicitly configured. */
+        if ( !nestedhvm_enabled(d) )
+        {
+            __clear_bit(X86_FEATURE_VMX, max_fs);
+            __clear_bit(X86_FEATURE_SVM, max_fs);
+        }
     }
 
     /*
diff --git a/xen/arch/x86/hvm/nestedhvm.c b/xen/arch/x86/hvm/nestedhvm.c
index a400d55..f2f7469 100644
--- a/xen/arch/x86/hvm/nestedhvm.c
+++ b/xen/arch/x86/hvm/nestedhvm.c
@@ -29,7 +29,8 @@ static unsigned long *shadow_io_bitmap[3];
 /* Nested HVM on/off per domain */
 bool nestedhvm_enabled(const struct domain *d)
 {
-    return is_hvm_domain(d) && d->arch.hvm_domain.params[HVM_PARAM_NESTEDHVM];
+    return is_hvm_domain(d) && d->arch.hvm_domain.params &&
+        d->arch.hvm_domain.params[HVM_PARAM_NESTEDHVM];
 }
 
 /* Nested VCPU */
-- 
2.1.4


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