hv: Explicitly trap VMXE and PCIDE bit for CR4 write

Now, we let guest own most CR4 bit. Which means guest
handles whether the CR4 writting is invalid or not and
GP injection if it's invalid writing.

Two bits are exception here:

we filter VMX and PCID feature to guest (which means
they are supported on native).

So we can't depends on guest to inject GP for these bits.
Instead, we should explicitly trap these CR4 bits update
and inject GP to guest from HV.

Signed-off-by: Yin Fengwei <fengwei.yin@intel.com>
Acked-by: Anthony Xu <anthony.xu@intel.com>

Author: fyin1

hypervisor/arch/x86/vmx.c

@@ -505,6 +505,23 @@ int vmx_write_cr3(struct vcpu *vcpu, uint64_t cr3)
 	return 0;
 }
 
+static bool is_cr4_write_valid(struct vcpu *vcpu, uint64_t cr4)
+{
+	/* Check if guest try to set fixed to 0 bits or reserved bits */
+	if ((cr4 & cr4_always_off_mask) != 0U)
+		return false;
+
+	/* Do NOT support nested guest */
+	if ((cr4 & CR4_VMXE) != 0UL)
+		return false;
+
+	/* Do NOT support PCID in guest */
+	if ((cr4 & CR4_PCIDE) != 0UL)
+		return false;
+
+	return true;
+}
+
 /*
  * Handling of CR4:
  * Assume "unrestricted guest" feature is supported by vmx.
@@ -529,10 +546,13 @@ int vmx_write_cr3(struct vcpu *vcpu, uint64_t cr3)
  *   - PCE (8) Flexible to guest
  *   - OSFXSR (9) Flexible to guest
  *   - OSXMMEXCPT (10) Flexible to guest
- *   - VMXE (13) must always be 1 => must lead to a VM exit
+ *   - VMXE (13) Trapped to hide from guest
  *   - SMXE (14) must always be 0 => must lead to a VM exit
- *   - PCIDE (17) Flexible to guest
+ *   - PCIDE (17) Trapped to hide from guest
  *   - OSXSAVE (18) Flexible to guest
+ *   - XSAVE (19) Flexible to guest
+ *   		We always keep align with physical cpu. So it's flexible to
+ *   		guest
  *   - SMEP (20) Flexible to guest
  *   - SMAP (21) Flexible to guest
  *   - PKE (22) Flexible to guest
@@ -543,19 +563,8 @@ int vmx_write_cr4(struct vcpu *vcpu, uint64_t cr4)
 		&vcpu->arch_vcpu.contexts[vcpu->arch_vcpu.cur_context];
 	uint64_t cr4_vmx;
 
-	/* TODO: Check all invalid guest statuses according to the change of
-	 * CR4, and inject a #GP to guest */
-
-	/* Check if guest try to set fixed to 0 bits or reserved bits */
-	if((cr4 & cr4_always_off_mask) != 0U) {
-		pr_err("Not allow to set reserved/always off bits for CR4");
-		vcpu_inject_gp(vcpu, 0U);
-		return 0;
-	}
-
-	/* Do NOT support nested guest */
-	if ((cr4 & CR4_VMXE) != 0UL) {
-		pr_err("Nested guest not supported");
+	if (!is_cr4_write_valid(vcpu, cr4)) {
+		pr_dbg("Invalid cr4 write operation from guest");
 		vcpu_inject_gp(vcpu, 0U);
 		return 0;
 	}

hypervisor/include/arch/x86/vmx.h

@@ -404,7 +404,7 @@
 			   CR0_NE |  CR0_ET | CR0_TS | CR0_EM | CR0_MP | CR0_PE)
 
 /* CR4 bits hv want to trap to track status change */
-#define CR4_TRAP_MASK (CR4_PSE | CR4_PAE)
+#define CR4_TRAP_MASK (CR4_PSE | CR4_PAE | CR4_VMXE | CR4_PCIDE)
 #define	CR4_RESERVED_MASK ~(CR4_VME | CR4_PVI | CR4_TSD | CR4_DE | CR4_PSE | \
 				CR4_PAE | CR4_MCE | CR4_PGE | CR4_PCE |	     \
 				CR4_OSFXSR | CR4_PCIDE | CR4_OSXSAVE |       \