x86: Clean up the Xen MSR infrastructure

Rename them to guest_{rd,wr}msr_xen() for consistency, and because the _regs
suffix isn't very appropriate.

Update them to take a vcpu pointer rather than presuming that they act on
current, and switch to using X86EMUL_* return values.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Sergey Dyasli <sergey.dyasli@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/msr.c

@@ -156,8 +156,7 @@ int guest_rdmsr(const struct vcpu *v, uint32_t msr, uint64_t *val)
 
         /* Fallthrough. */
     case 0x40000200 ... 0x400002ff:
-        ret = (rdmsr_hypervisor_regs(msr, val)
-               ? X86EMUL_OKAY : X86EMUL_EXCEPTION);
+        ret = guest_rdmsr_xen(v, msr, val);
         break;
 
     default:
@@ -283,12 +282,7 @@ int guest_wrmsr(struct vcpu *v, uint32_t msr, uint64_t val)
 
         /* Fallthrough. */
     case 0x40000200 ... 0x400002ff:
-        switch ( wrmsr_hypervisor_regs(msr, val) )
-        {
-        case -ERESTART: ret = X86EMUL_RETRY;     break;
-        case 1:         ret = X86EMUL_OKAY;      break;
-        default:        ret = X86EMUL_EXCEPTION; break;
-        }
+        ret = guest_wrmsr_xen(v, msr, val);
         break;
 
     default:

xen/arch/x86/traps.c

@@ -768,29 +768,25 @@ static void do_trap(struct cpu_user_regs *regs)
           trapnr, trapstr(trapnr), regs->error_code);
 }
 
-/* Returns 0 if not handled, and non-0 for success. */
-int rdmsr_hypervisor_regs(uint32_t idx, uint64_t *val)
+int guest_rdmsr_xen(const struct vcpu *v, uint32_t idx, uint64_t *val)
 {
-    struct domain *d = current->domain;
+    const struct domain *d = v->domain;
     /* Optionally shift out of the way of Viridian architectural MSRs. */
     uint32_t base = is_viridian_domain(d) ? 0x40000200 : 0x40000000;
 
     switch ( idx - base )
     {
     case 0: /* Write hypercall page MSR.  Read as zero. */
-    {
         *val = 0;
-        return 1;
-    }
+        return X86EMUL_OKAY;
     }
 
-    return 0;
+    return X86EMUL_EXCEPTION;
 }
 
-/* Returns 1 if handled, 0 if not and -Exx for error. */
-int wrmsr_hypervisor_regs(uint32_t idx, uint64_t val)
+int guest_wrmsr_xen(struct vcpu *v, uint32_t idx, uint64_t val)
 {
-    struct domain *d = current->domain;
+    struct domain *d = v->domain;
     /* Optionally shift out of the way of Viridian architectural MSRs. */
     uint32_t base = is_viridian_domain(d) ? 0x40000200 : 0x40000000;
 
@@ -809,7 +805,7 @@ int wrmsr_hypervisor_regs(uint32_t idx, uint64_t val)
             gdprintk(XENLOG_WARNING,
                      "wrmsr hypercall page index %#x unsupported\n",
                      page_index);
-            return 0;
+            return X86EMUL_EXCEPTION;
         }
 
         page = get_page_from_gfn(d, gmfn, &t, P2M_ALLOC);
@@ -822,13 +818,13 @@ int wrmsr_hypervisor_regs(uint32_t idx, uint64_t val)
             if ( p2m_is_paging(t) )
             {
                 p2m_mem_paging_populate(d, gmfn);
-                return -ERESTART;
+                return X86EMUL_RETRY;
             }
 
             gdprintk(XENLOG_WARNING,
                      "Bad GMFN %lx (MFN %#"PRI_mfn") to MSR %08x\n",
                      gmfn, mfn_x(page ? page_to_mfn(page) : INVALID_MFN), base);
-            return 0;
+            return X86EMUL_EXCEPTION;
         }
 
         hypercall_page = __map_domain_page(page);
@@ -836,11 +832,12 @@ int wrmsr_hypervisor_regs(uint32_t idx, uint64_t val)
         unmap_domain_page(hypercall_page);
 
         put_page_and_type(page);
-        return 1;
-    }
+        return X86EMUL_OKAY;
     }
 
-    return 0;
+    default:
+        return X86EMUL_EXCEPTION;
+    }
 }
 
 void cpuid_hypervisor_leaves(const struct vcpu *v, uint32_t leaf,

xen/include/asm-x86/processor.h

@@ -554,8 +554,8 @@ unsigned long alloc_stub_page(unsigned int cpu, unsigned long *mfn);
 
 void cpuid_hypervisor_leaves(const struct vcpu *v, uint32_t leaf,
                              uint32_t subleaf, struct cpuid_leaf *res);
-int rdmsr_hypervisor_regs(uint32_t idx, uint64_t *val);
-int wrmsr_hypervisor_regs(uint32_t idx, uint64_t val);
+int guest_rdmsr_xen(const struct vcpu *v, uint32_t idx, uint64_t *val);
+int guest_wrmsr_xen(struct vcpu *v, uint32_t idx, uint64_t val);
 
 void microcode_set_module(unsigned int);
 int microcode_update(XEN_GUEST_HANDLE_PARAM(const_void), unsigned long len);