x86/msr: fix X2APIC_LAST

The latest Intel manual now says the X2APIC reserved range is only
0x800 to 0x8ff (NOT 0xbff).
This changed between SDM 68 (Nov 2018) and SDM 69 (Jan 2019).
The AMD manual documents 0x800-0x8ff too.

There are non-X2APIC MSRs in the 0x900-0xbff range now:
e.g. 0x981 is IA32_TME_CAPABILITY, an architectural MSR.

The new MSR in this range appears to have been introduced in Icelake,
so this commit should be backported to Xen versions supporting Icelake.

Backport: 4.13+

Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/hvm/vmx/vmx.c

@@ -3397,7 +3397,7 @@ void vmx_vlapic_msr_changed(struct vcpu *v)
             if ( cpu_has_vmx_apic_reg_virt )
             {
                 for ( msr = MSR_X2APIC_FIRST;
-                      msr <= MSR_X2APIC_FIRST + 0xff; msr++ )
+                      msr <= MSR_X2APIC_LAST; msr++ )
                     vmx_clear_msr_intercept(v, msr, VMX_MSR_R);
 
                 vmx_set_msr_intercept(v, MSR_X2APIC_PPR, VMX_MSR_R);
@@ -3418,7 +3418,7 @@ void vmx_vlapic_msr_changed(struct vcpu *v)
     if ( !(v->arch.hvm.vmx.secondary_exec_control &
            SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE) )
         for ( msr = MSR_X2APIC_FIRST;
-              msr <= MSR_X2APIC_FIRST + 0xff; msr++ )
+              msr <= MSR_X2APIC_LAST; msr++ )
             vmx_set_msr_intercept(v, msr, VMX_MSR_RW);
 
     vmx_update_secondary_exec_control(v);

xen/arch/x86/include/asm/msr-index.h

@@ -148,7 +148,7 @@
 #define MSR_INTERRUPT_SSP_TABLE             0x000006a8
 
 #define MSR_X2APIC_FIRST                    0x00000800
-#define MSR_X2APIC_LAST                     0x00000bff
+#define MSR_X2APIC_LAST                     0x000008ff
 
 #define MSR_X2APIC_TPR                      0x00000808
 #define MSR_X2APIC_PPR                      0x0000080a