Fix PV CPUID virtualization of XSave

The patch will fix XSave CPUID virtualization for PV guests. The XSave
area size returned by CPUID leaf D is changed dynamically depending on
the XCR0. Tools/libxc only assigns a static value. The fix will adjust
xsave area size during runtime.

Note: This fix is already in HVM cpuid virtualization. And Dom0 is not
affected, either.

Signed-off-by:  Shan Haitao <haitao.shan@intel.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 183ce91b74..0203613b53 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -770,6 +770,30 @@ static void pv_cpuid(struct cpu_user_regs *regs)
     {
         if ( !cpuid_hypervisor_leaves(a, c, &a, &b, &c, &d) )
             domain_cpuid(current->domain, a, c, &a, &b, &c, &d);
+
+        switch ( a )
+        {
+        case 0xd:
+        {
+            unsigned int sub_leaf, _eax, _ebx, _ecx, _edx;
+            /* EBX value of main leaf 0 depends on enabled xsave features */
+            if ( c == 0 && current->arch.xcr0 )
+            {
+                /* reset EBX to default value first */
+                b = XSTATE_AREA_MIN_SIZE;
+                for ( sub_leaf = 2; sub_leaf < 63; sub_leaf++ )
+                {
+                    if ( !(current->arch.xcr0 & (1ULL << sub_leaf)) )
+                        continue;
+                    domain_cpuid(current->domain, a, c, &_eax, &_ebx, &_ecx,
+                                 &_edx);
+                    if ( (_eax + _ebx) > b )
+                        b = _eax + _ebx;
+                }
+            }
+        break;
+        }
+        }
         goto out;
     }