1 files changed, 44 insertions, 6 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 75b7a0f90380..da33e0c5870d 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -168,21 +168,23 @@ static void __init xen_banner(void)
                xen_feature(XENFEAT_mmu_pt_update_preserve_ad) ? " (preserve-AD)" : "");
 }
 
+static __read_mostly unsigned int cpuid_leaf1_edx_mask = ~0;
+static __read_mostly unsigned int cpuid_leaf1_ecx_mask = ~0;
+
 static void xen_cpuid(unsigned int *ax, unsigned int *bx,
                       unsigned int *cx, unsigned int *dx)
 {
+        unsigned maskecx = ~0;
         unsigned maskedx = ~0;
 
         /*
          * Mask out inconvenient features, to try and disable as many
          * unsupported kernel subsystems as possible.
          */
-        if (*ax == 1)
-                maskedx = ~((1 << X86_FEATURE_APIC) |  /* disable APIC */
-                            (1 << X86_FEATURE_ACPI) |  /* disable ACPI */
-                            (1 << X86_FEATURE_MCE)  |  /* disable MCE */
-                            (1 << X86_FEATURE_MCA)  |  /* disable MCA */
-                            (1 << X86_FEATURE_ACC));   /* thermal monitoring */
+        if (*ax == 1) {
+                maskecx = cpuid_leaf1_ecx_mask;
+                maskedx = cpuid_leaf1_edx_mask;
+        }
 
         asm(XEN_EMULATE_PREFIX "cpuid"
                 : "=a" (*ax),
@@ -190,9 +192,43 @@ static void xen_cpuid(unsigned int *ax, unsigned int *bx,
                   "=c" (*cx),
                   "=d" (*dx)
                 : "0" (*ax), "2" (*cx));
+
+        *cx &= maskecx;
         *dx &= maskedx;
 }
 
+static __init void xen_init_cpuid_mask(void)
+{
+        unsigned int ax, bx, cx, dx;
+
+        cpuid_leaf1_edx_mask =
+                ~((1 << X86_FEATURE_MCE)  |  /* disable MCE */
+                  (1 << X86_FEATURE_MCA)  |  /* disable MCA */
+                  (1 << X86_FEATURE_ACC));   /* thermal monitoring */
+
+        if (!xen_initial_domain())
+                cpuid_leaf1_edx_mask &=
+                        ~((1 << X86_FEATURE_APIC) |  /* disable local APIC */
+                          (1 << X86_FEATURE_ACPI));  /* disable ACPI */
+
+        ax = 1;
+        xen_cpuid(&ax, &bx, &cx, &dx);
+
+        /* cpuid claims we support xsave; try enabling it to see what happens */
+        if (cx & (1 << (X86_FEATURE_XSAVE % 32))) {
+                unsigned long cr4;
+
+                set_in_cr4(X86_CR4_OSXSAVE);
+                
+                cr4 = read_cr4();
+
+                if ((cr4 & X86_CR4_OSXSAVE) == 0)
+                        cpuid_leaf1_ecx_mask &= ~(1 << (X86_FEATURE_XSAVE % 32));
+
+                clear_in_cr4(X86_CR4_OSXSAVE);
+        }
+}
+
 static void xen_set_debugreg(int reg, unsigned long val)
 {
         HYPERVISOR_set_debugreg(reg, val);
@@ -901,6 +937,8 @@ asmlinkage void __init xen_start_kernel(void)
 
         xen_init_irq_ops();
 
+        xen_init_cpuid_mask();
+
 #ifdef CONFIG_X86_LOCAL_APIC
         /*
          * set up the basic apic ops.