[Xen-devel] [PATCH 1/3] vvmx: set vmxon_region_pa of vcpu out of VMX operation to an invalid address

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

nvmx_handle_vmxon() previously checks whether a vcpu is in VMX
operation by comparing its vmxon_region_pa with GPA 0. However, 0 is
also a valid VMXON region address. If L1 hypervisor had set the VMXON
region address to 0, the check in nvmx_handle_vmxon() will be skipped.
Fix this problem by using an invalid VMXON region address for vcpu
out of VMX operation.

Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vvmx.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c
index e6e9ebd..f5637eb 100644
--- a/xen/arch/x86/hvm/vmx/vvmx.c
+++ b/xen/arch/x86/hvm/vmx/vvmx.c
@@ -32,6 +32,18 @@ static DEFINE_PER_CPU(u64 *, vvmcs_buf);
 
 static void nvmx_purge_vvmcs(struct vcpu *v);
 
+/*
+ * When a vcpu is out of VMXON region, set its vmxon_region_pa to
+ * INVALID_VMXON_REGION_PA. We cannot use 0, because 0 is also a valid
+ * VMXON region address.
+ */
+#define INVALID_VMXON_REGION_PA (~0UL)
+
+static bool nvmx_vcpu_in_vmx(struct vcpu *v)
+{
+    return vcpu_2_nvmx(v).vmxon_region_pa != INVALID_VMXON_REGION_PA;
+}
+
 #define VMCS_BUF_SIZE 100
 
 int nvmx_cpu_up_prepare(unsigned int cpu)
@@ -107,7 +119,7 @@ int nvmx_vcpu_initialise(struct vcpu *v)
 
     nvmx->ept.enabled = 0;
     nvmx->guest_vpid = 0;
-    nvmx->vmxon_region_pa = 0;
+    nvmx->vmxon_region_pa = INVALID_VMXON_REGION_PA;
     nvcpu->nv_vvmcx = NULL;
     nvcpu->nv_vvmcxaddr = VMCX_EADDR;
     nvmx->intr.intr_info = 0;
@@ -357,7 +369,7 @@ static int vmx_inst_check_privilege(struct cpu_user_regs 
*regs, int vmxop_check)
              !(v->arch.hvm_vcpu.guest_cr[4] & X86_CR4_VMXE) )
             goto invalid_op;
     }
-    else if ( !vcpu_2_nvmx(v).vmxon_region_pa )
+    else if ( !nvmx_vcpu_in_vmx(v) )
         goto invalid_op;
 
     hvm_get_segment_register(v, x86_seg_cs, &cs);
@@ -1384,7 +1396,7 @@ int nvmx_handle_vmxon(struct cpu_user_regs *regs)
     if ( rc != X86EMUL_OKAY )
         return rc;
 
-    if ( nvmx->vmxon_region_pa )
+    if ( nvmx_vcpu_in_vmx(v) )
         gdprintk(XENLOG_WARNING, 
                  "vmxon again: orig %"PRIpaddr" new %lx\n",
                  nvmx->vmxon_region_pa, gpa);
@@ -1417,7 +1429,7 @@ int nvmx_handle_vmxoff(struct cpu_user_regs *regs)
         return rc;
 
     nvmx_purge_vvmcs(v);
-    nvmx->vmxon_region_pa = 0;
+    nvmx->vmxon_region_pa = INVALID_VMXON_REGION_PA;
 
     vmreturn(regs, VMSUCCEED);
     return X86EMUL_OKAY;
-- 
2.10.1


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