[PATCH 3/3] vm_event: vmx: Allow intercepting hypervisor MSRs in debug builds

[Teddy Astie <teddy.astie@xxxxxxxxxx>]

MSRs that are not covered by MSR bitmap (e.g hypervisor range) are
unconditionally intercepted by hardware and don't need any specific handling.

However, vmx_set_msr_intercept() wrongly ASSERT() if the MSR is a part of the
hypervisor range. Fix it by skipping the ASSERT() in this case.

This is only reachable with CONFIG_VM_EVENT using 
XEN_DOMCTL_MONITOR_EVENT_MOV_TO_MSR
to configure a MSR intercept in the hypervisor range (0x40000000–0x40001fff).

Fixes: 62999081ca27 ("x86/vmx: Introduce and use struct vmx_msr_bitmap")
Signed-off-by: Teddy Astie <teddy.astie@xxxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vmcs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index 8e52ef4d49..050168bbce 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -986,7 +986,7 @@ void vmx_set_msr_intercept(struct vcpu *v, unsigned int msr,
         if ( type & VMX_MSR_W )
             set_bit(msr, msr_bitmap->write_high);
     }
-    else
+    else if ( !((msr >= 0x40000000U) && (msr <= 0x40001fffU)) )
         ASSERT(!"MSR out of range for interception\n");
 }
 
-- 
2.55.0



--
Teddy Astie | Vates XCP-ng Developer

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