x86/hvm: indicate avaliability of HW support of APIC virtualization to HVM guests

Set bits in hypervisor CPUID leaf indicating that HW provides (and the
hypervisor enables) HW support for APIC and x2APIC virtualization.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-off-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index ecdbc17b86284950f8db8c4e44fa0e6c54f49d95..00cab8aa9615070d33db0acef50d0607a0da1807 100644 (file)
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -57,6 +57,7 @@
 #include <asm/apic.h>
 #include <asm/hvm/nestedhvm.h>
 #include <asm/event.h>
+#include <public/arch-x86/cpuid.h>
 
 static bool_t __initdata opt_force_ept;
 boolean_param("force-ept", opt_force_ept);
@@ -1655,6 +1656,24 @@ static void vmx_handle_eoi(u8 vector)
     __vmwrite(GUEST_INTR_STATUS, status);
 }
 
+void vmx_hypervisor_cpuid_leaf(uint32_t sub_idx,
+                               uint32_t *eax, uint32_t *ebx,
+                               uint32_t *ecx, uint32_t *edx)
+{
+    if ( sub_idx != 0 )
+        return;
+    if ( cpu_has_vmx_apic_reg_virt )
+        *eax |= XEN_HVM_CPUID_APIC_ACCESS_VIRT;
+    /*
+     * We want to claim that x2APIC is virtualized if APIC MSR accesses are
+     * not intercepted. When all three of these are true both rdmsr and wrmsr
+     * in the guest will run without VMEXITs (see vmx_vlapic_msr_changed()).
+     */
+    if ( cpu_has_vmx_virtualize_x2apic_mode && cpu_has_vmx_apic_reg_virt &&
+         cpu_has_vmx_virtual_intr_delivery )
+        *eax |= XEN_HVM_CPUID_X2APIC_VIRT;
+}
+
 static struct hvm_function_table __initdata vmx_function_table = {
     .name                 = "VMX",
     .cpu_up_prepare       = vmx_cpu_up_prepare,
@@ -1712,6 +1731,7 @@ static struct hvm_function_table __initdata vmx_function_table = {
     .sync_pir_to_irr      = vmx_sync_pir_to_irr,
     .handle_eoi           = vmx_handle_eoi,
     .nhvm_hap_walk_L1_p2m = nvmx_hap_walk_L1_p2m,
+    .hypervisor_cpuid_leaf = vmx_hypervisor_cpuid_leaf,
 };
 
 const struct hvm_function_table * __init start_vmx(void)

diff --git a/xen/include/public/arch-x86/cpuid.h b/xen/include/public/arch-x86/cpuid.h
index fff972acc996a07decd9a5a7fd94d437b510e960..7135d5456bfd954a57b71b59023e2fb21e31e691 100644 (file)
--- a/xen/include/public/arch-x86/cpuid.h
+++ b/xen/include/public/arch-x86/cpuid.h
@@ -70,6 +70,10 @@
  * HVM-specific features
  */
 
+/* EAX Features */
+#define XEN_HVM_CPUID_APIC_ACCESS_VIRT (1u << 0) /* Virtualized APIC registers */
+#define XEN_HVM_CPUID_X2APIC_VIRT      (1u << 1) /* Virtualized x2APIC accesses */
+
 #define XEN_CPUID_MAX_NUM_LEAVES 4
 
 #endif /* __XEN_PUBLIC_ARCH_X86_CPUID_H__ */