x86/msr: Fix fallout from mostly c/s 832c180

* Fix the shim build by providing a !CONFIG_HVM declaration for
   hvm_get_guest_bndcfgs(), and removing the introduced
   ASSERT(is_hvm_domain(d))'s.  They are needed for DCE to keep the build
   working.  Furthermore, in this way, the risk of runtime type confusion is
   removed.
 * Revert the de-const'ing of the vcpu pointer in vmx_get_guest_bndcfgs().
   vmx_vmcs_enter() really does mutate the vcpu, and may cause it to undergo a
   full de/reschedule, which is contrary to the programmers expectation of
   hvm_get_guest_bndcfgs().  guest_rdmsr() was always going to need to lose
   its const parameter, and this was the correct time for it to happen.
 * The MSRs in vcpu_msrs are in numeric order.  Re-position XSS to match.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/hvm/vmx/vmx.c

@@ -1150,11 +1150,8 @@ static bool vmx_set_guest_bndcfgs(struct vcpu *v, u64 val)
     return true;
 }
 
-static bool vmx_get_guest_bndcfgs(const struct vcpu *cv, u64 *val)
+static bool vmx_get_guest_bndcfgs(struct vcpu *v, u64 *val)
 {
-    /* Get a non-const pointer for vmx_vmcs_enter() */
-    struct vcpu *v = cv->domain->vcpu[cv->vcpu_id];
-
     ASSERT(cpu_has_mpx && cpu_has_vmx_mpx);
 
     vmx_vmcs_enter(v);

xen/arch/x86/msr.c

@@ -115,7 +115,7 @@ int init_vcpu_msr_policy(struct vcpu *v)
     return 0;
 }
 
-int guest_rdmsr(const struct vcpu *v, uint32_t msr, uint64_t *val)
+int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t *val)
 {
     const struct vcpu *curr = current;
     const struct domain *d = v->domain;
@@ -182,13 +182,9 @@ int guest_rdmsr(const struct vcpu *v, uint32_t msr, uint64_t *val)
         break;
 
     case MSR_IA32_BNDCFGS:
-        if ( !cp->feat.mpx )
+        if ( !cp->feat.mpx || !is_hvm_domain(d) ||
+             !hvm_get_guest_bndcfgs(v, val) )
             goto gp_fault;
-
-        ASSERT(is_hvm_domain(d));
-        if (!hvm_get_guest_bndcfgs(v, val) )
-            goto gp_fault;
-
         break;
 
     case MSR_IA32_XSS:
@@ -375,13 +371,9 @@ int guest_wrmsr(struct vcpu *v, uint32_t msr, uint64_t val)
         break;
 
     case MSR_IA32_BNDCFGS:
-        if ( !cp->feat.mpx )
+        if ( !cp->feat.mpx || !is_hvm_domain(d) ||
+             !hvm_set_guest_bndcfgs(v, val) )
             goto gp_fault;
-
-        ASSERT(is_hvm_domain(d));
-        if ( !hvm_set_guest_bndcfgs(v, val) )
-            goto gp_fault;
-
         break;
 
     case MSR_IA32_XSS:

xen/arch/x86/pv/emul-priv-op.c

@@ -819,7 +819,7 @@ static inline bool is_cpufreq_controller(const struct domain *d)
 static int read_msr(unsigned int reg, uint64_t *val,
                     struct x86_emulate_ctxt *ctxt)
 {
-    const struct vcpu *curr = current;
+    struct vcpu *curr = current;
     const struct domain *currd = curr->domain;
     bool vpmu_msr = false;
     int ret;

xen/include/asm-x86/hvm/hvm.h

@@ -145,7 +145,7 @@ struct hvm_function_table {
     int  (*get_guest_pat)(struct vcpu *v, u64 *);
     int  (*set_guest_pat)(struct vcpu *v, u64);
 
-    bool (*get_guest_bndcfgs)(const struct vcpu *v, u64 *);
+    bool (*get_guest_bndcfgs)(struct vcpu *v, u64 *);
     bool (*set_guest_bndcfgs)(struct vcpu *v, u64);
 
     void (*set_tsc_offset)(struct vcpu *v, u64 offset, u64 at_tsc);
@@ -444,7 +444,7 @@ static inline unsigned long hvm_get_shadow_gs_base(struct vcpu *v)
     return hvm_funcs.get_shadow_gs_base(v);
 }
 
-static inline bool hvm_get_guest_bndcfgs(const struct vcpu *v, u64 *val)
+static inline bool hvm_get_guest_bndcfgs(struct vcpu *v, u64 *val)
 {
     return hvm_funcs.get_guest_bndcfgs &&
            hvm_funcs.get_guest_bndcfgs(v, val);
@@ -692,6 +692,7 @@ unsigned long hvm_get_shadow_gs_base(struct vcpu *v);
 void hvm_set_info_guest(struct vcpu *v);
 void hvm_cpuid_policy_changed(struct vcpu *v);
 void hvm_set_tsc_offset(struct vcpu *v, uint64_t offset, uint64_t at_tsc);
+bool hvm_get_guest_bndcfgs(struct vcpu *v, uint64_t *val);
 
 /* End of prototype list */
 

xen/include/asm-x86/msr.h

@@ -296,6 +296,11 @@ struct vcpu_msrs
         };
     } misc_features_enables;
 
+    /* 0x00000da0 - MSR_IA32_XSS */
+    struct {
+        uint64_t raw;
+    } xss;
+
     /*
      * 0xc0000103 - MSR_TSC_AUX
      *
@@ -313,11 +318,6 @@ struct vcpu_msrs
      * values here may be stale in current context.
      */
     uint32_t dr_mask[4];
-
-    /* 0x00000da0 - MSR_IA32_XSS */
-    struct {
-        uint64_t raw;
-    } xss;
 };
 
 void init_guest_msr_policy(void);
@@ -333,7 +333,7 @@ int init_vcpu_msr_policy(struct vcpu *v);
  * These functions are also used by the migration logic, so need to cope with
  * being used outside of v's context.
  */
-int guest_rdmsr(const struct vcpu *v, uint32_t msr, uint64_t *val);
+int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t *val);
 int guest_wrmsr(struct vcpu *v, uint32_t msr, uint64_t val);
 
 #endif /* !__ASSEMBLY__ */