[PATCH] x86/vmx: Remove IO bitmap from minimal VMX requirements

[Hubert Jasudowicz <hubert.jasudowicz@xxxxxxx>]

This patch is a result of a downstream bug report[1]. Xen fails to
create a HVM domain while running under VMware Fusion 12.1.0 on
a modern Intel Core i9 CPU:

(XEN) VMX: CPU0 has insufficient CPU-Based Exec Control (b5b9fffe; requires 
2299968c)
(XEN) VMX: failed to initialise.

It seems that Apple hypervisor API doesn't support this feature[2].

Move this bit from minimal required features to optional.

[1] https://github.com/CERT-Polska/drakvuf-sandbox/issues/418
[2] https://developer.apple.com/documentation/hypervisor/cpu_based_io_bitmaps

Signed-off-by: Hubert Jasudowicz <hubert.jasudowicz@xxxxxxx>
---
 xen/arch/x86/hvm/vmx/vmcs.c        | 8 +++++---
 xen/include/asm-x86/hvm/vmx/vmcs.h | 2 ++
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index 164535f8f0..bad4d6e206 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -276,10 +276,10 @@ static int vmx_init_vmcs_config(void)
            CPU_BASED_MONITOR_EXITING |
            CPU_BASED_MWAIT_EXITING |
            CPU_BASED_MOV_DR_EXITING |
-           CPU_BASED_ACTIVATE_IO_BITMAP |
            CPU_BASED_USE_TSC_OFFSETING |
            CPU_BASED_RDTSC_EXITING);
     opt = (CPU_BASED_ACTIVATE_MSR_BITMAP |
+           CPU_BASED_ACTIVATE_IO_BITMAP |
            CPU_BASED_TPR_SHADOW |
            CPU_BASED_MONITOR_TRAP_FLAG |
            CPU_BASED_ACTIVATE_SECONDARY_CONTROLS);
@@ -1168,8 +1168,10 @@ static int construct_vmcs(struct vcpu *v)
     }
 
     /* I/O access bitmap. */
-    __vmwrite(IO_BITMAP_A, __pa(d->arch.hvm.io_bitmap));
-    __vmwrite(IO_BITMAP_B, __pa(d->arch.hvm.io_bitmap) + PAGE_SIZE);
+    if ( cpu_has_vmx_io_bitmap ) {
+        __vmwrite(IO_BITMAP_A, __pa(d->arch.hvm.io_bitmap));
+        __vmwrite(IO_BITMAP_B, __pa(d->arch.hvm.io_bitmap) + PAGE_SIZE);
+    }
 
     if ( cpu_has_vmx_virtual_intr_delivery )
     {
diff --git a/xen/include/asm-x86/hvm/vmx/vmcs.h 
b/xen/include/asm-x86/hvm/vmx/vmcs.h
index 906810592f..b00830a5b3 100644
--- a/xen/include/asm-x86/hvm/vmx/vmcs.h
+++ b/xen/include/asm-x86/hvm/vmx/vmcs.h
@@ -342,6 +342,8 @@ extern u64 vmx_ept_vpid_cap;
     (vmx_secondary_exec_control & SECONDARY_EXEC_XSAVES)
 #define cpu_has_vmx_tsc_scaling \
     (vmx_secondary_exec_control & SECONDARY_EXEC_TSC_SCALING)
+#define cpu_has_vmx_io_bitmap \
+    (vmx_cpu_based_exec_control & CPU_BASED_ACTIVATE_IO_BITMAP)
 
 #define VMCS_RID_TYPE_MASK              0x80000000
 
-- 
2.30.0