[PATCH v2 1/4] vvmx: set vmxon_region_pa of vcpu out of VMX operation to an invalid address

[Haozhong Zhang <haozhong.zhang@intel.com>]

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@intel.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>
---
 xen/arch/x86/hvm/vmx/vvmx.c        | 13 +++++++++----
 xen/include/asm-x86/hvm/vmx/vvmx.h |  7 +++++++
 2 files 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..eae8150 100644
--- a/xen/arch/x86/hvm/vmx/vvmx.c
+++ b/xen/arch/x86/hvm/vmx/vvmx.c
@@ -32,6 +32,11 @@ static DEFINE_PER_CPU(u64 *, vvmcs_buf);
 
 static void nvmx_purge_vvmcs(struct vcpu *v);
 
+static bool nvmx_vcpu_in_vmx(const struct vcpu *v)
+{
+    return vcpu_2_nvmx(v).vmxon_region_pa != INVALID_PADDR;
+}
+
 #define VMCS_BUF_SIZE 100
 
 int nvmx_cpu_up_prepare(unsigned int cpu)
@@ -107,7 +112,7 @@ 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_PADDR;
     nvcpu->nv_vvmcx = NULL;
     nvcpu->nv_vvmcxaddr = VMCX_EADDR;
     nvmx->intr.intr_info = 0;
@@ -357,7 +362,7 @@ 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 +1389,7 @@ 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 +1422,7 @@ 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_PADDR;
 
     vmreturn(regs, VMSUCCEED);
     return X86EMUL_OKAY;
diff --git a/xen/include/asm-x86/hvm/vmx/vvmx.h b/xen/include/asm-x86/hvm/vmx/vvmx.h
index ead586e..af7702b 100644
--- a/xen/include/asm-x86/hvm/vmx/vvmx.h
+++ b/xen/include/asm-x86/hvm/vmx/vvmx.h
@@ -28,6 +28,13 @@ struct vvmcs_list {
 };
 
 struct nestedvmx {
+    /*
+     * vmxon_region_pa is also used to indicate whether a vcpu is in
+     * the VMX operation. When a vcpu is out of the VMX operation, its
+     * vmxon_region_pa is set to an invalid address INVALID_PADDR. We
+     * cannot use 0 for this purpose, because it's a valid VMXON region
+     * address.
+     */
     paddr_t    vmxon_region_pa;
     void       *iobitmap[2];		/* map (va) of L1 guest I/O bitmap */
     void       *msrbitmap;		/* map (va) of L1 guest MSR bitmap */
-- 
2.10.1


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