[Xen-devel] [PATCH 5/6] x86/cpuid: Don't offer HVM hypervisor leaves to PV guests

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Xen leaf 4 is HVM-only.  Report a lower max_leaf to PV guests, so they don't
go and investigate a leaf which will return all zeros.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
---
 xen/arch/x86/traps.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 4f29c3a..51bcd97 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -911,12 +911,16 @@ void cpuid_hypervisor_leaves(const struct vcpu *v, 
uint32_t leaf,
     uint32_t idx  = leaf - base;
     unsigned int limit = is_viridian_domain(d) ? p->hv2_limit : p->hv_limit;
 
+    /* Current, HVM max leaf is 4 and PV max leaf is 3. */
+    unsigned int max_leaf = has_hvm_container_domain(d) ? 4 : 3;
+    BUILD_BUG_ON(XEN_CPUID_MAX_NUM_LEAVES != 4);
+
     if ( limit == 0 )
         /* Default number of leaves */
-        limit = XEN_CPUID_MAX_NUM_LEAVES;
+        limit = max_leaf;
     else
-        /* Clamp toolstack value between 2 and MAX_NUM_LEAVES. */
-        limit = min(max(limit, 2u), XEN_CPUID_MAX_NUM_LEAVES + 0u);
+        /* Clamp toolstack value between 2 and max_leaf. */
+        limit = min(max(limit, 2u), max_leaf);
 
     if ( idx > limit )
         return;
-- 
2.1.4


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