[Xen-devel] [PATCH] x86: Correctly report max number of hypervisor leaves

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

Commit def0bbd31 provided support for changing max number of
hypervisor cpuid leaves (in leaf 0x4000xx00). It also made the
hypervisor incorrectly report this number for guests that
use default value (i.e. don't specify leaf 0x4000xx00 in config
file)

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Reported-by: Roger Pau Monne <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/traps.c |   16 +++++++++++-----
 1 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 1722912..b82b1b3 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -692,13 +692,19 @@ int cpuid_hypervisor_leaves( uint32_t idx, uint32_t 
sub_idx,
     if ( idx > XEN_CPUID_MAX_NUM_LEAVES )
         return 0; /* Avoid unnecessary pass through domain_cpuid() */
 
-    /* Number of leaves may be user-specified */
     domain_cpuid(d, base, 0, &limit, &dummy, &dummy, &dummy);
-    limit &= 0xff;
-    if ( limit < 2 )
-        limit = 2;
-    else if ( limit > XEN_CPUID_MAX_NUM_LEAVES )
+    if ( limit == 0 )
+        /* Default number of leaves */
         limit = XEN_CPUID_MAX_NUM_LEAVES;
+    else
+    {
+        /* User-specified number of leaves */
+        limit &= 0xff;
+        if ( limit < 2 )
+            limit = 2;
+        else if ( limit > XEN_CPUID_MAX_NUM_LEAVES )
+            limit = XEN_CPUID_MAX_NUM_LEAVES;
+    }
 
     if ( idx > limit ) 
         return 0;
-- 
1.7.1


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