x86/msr: Change wrmsr() to take a single parameter

Mirroring the cleanup to rdmsr(), do the same to wrmsr().  It now has the same
API as wrmsrl(), but we'll want to drop that wrapper in due course.

It's telling that almost all remaining users pass in 0.  Most are converted
directly to WRMSRNS, but a few are not.

MSR_VIRT_SPEC_CTRL is unconditionally intercepted and is orders of magnitude
more expensive than just serialising.  In disable_lapic_nmi_watchdog(), the P4
case won't run on hardware which has anything more than plain WRMSR.

For CTR_WRITE() in op_model_athlon.c there is a logical change in behaviour,
but it's fixing a bug.  Peformance counters typically get written to -(count)
as they generate an interrupt on overflow.  The performance counters even in
the K8 were 48 bits wide, and this wrmsr() not being a wrmsrl() appears to
have been an oversight in commit b5103d692a ("x86 oprofile: use
rdmsrl/wrmsrl") which converted all other users, and appears to be the last
time there was an attempt to unify the MSR APIs.

No practical change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
(cherry picked from commit 389347a75f)

xen/arch/x86/cpu/amd.c

@@ -895,7 +895,7 @@ void amd_set_legacy_ssbd(bool enable)
 		return;
 
 	if (cpu_has_virt_ssbd)
-		wrmsr(MSR_VIRT_SPEC_CTRL, enable ? SPEC_CTRL_SSBD : 0, 0);
+		wrmsr(MSR_VIRT_SPEC_CTRL, enable ? SPEC_CTRL_SSBD : 0);
 	else if (amd_legacy_ssbd)
 		core_set_legacy_ssbd(enable);
 	else

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

@@ -754,7 +754,7 @@ static int _vmx_cpu_up(bool bsp)
         eax |= IA32_FEATURE_CONTROL_ENABLE_VMXON_OUTSIDE_SMX;
         if ( test_bit(X86_FEATURE_SMX, &boot_cpu_data.x86_capability) )
             eax |= IA32_FEATURE_CONTROL_ENABLE_VMXON_INSIDE_SMX;
-        wrmsr(MSR_IA32_FEATURE_CONTROL, eax, 0);
+        wrmsrns(MSR_IA32_FEATURE_CONTROL, eax);
     }
 
     if ( (rc = vmx_init_vmcs_config(bsp)) != 0 )

xen/arch/x86/include/asm/msr.h

@@ -15,13 +15,17 @@
  *   uint64_t foo = rdmsr(MSR_BAR);
  *   wrmsrns(MSR_BAR, foo);
  *
+ * and, if architectural serialisaition is necessary, or there are other
+ * reasons that WRMSRNS is inapplicable, then:
+ *
+ *   wrmsr(MSR_BAR, foo);
+ *
  * In addition, *_safe() wrappers exist to cope gracefully with a #GP.
  *
  *
  * All legacy forms are to be phased out:
  *
  *  rdmsrl(MSR_FOO, val);
- *  wrmsr(MSR_FOO, lo, hi);
  *  wrmsrl(MSR_FOO, val);
  */
 
@@ -43,17 +47,13 @@ static always_inline uint64_t rdmsr(unsigned int msr)
        val = a__ | ((u64)b__<<32); \
 } while(0)
 
-#define wrmsr(msr,val1,val2) \
-     __asm__ __volatile__("wrmsr" \
-			  : /* no outputs */ \
-			  : "c" (msr), "a" (val1), "d" (val2))
-
-static inline void wrmsrl(unsigned int msr, uint64_t val)
+static inline void wrmsr(unsigned int msr, uint64_t val)
 {
-        uint32_t lo = val, hi = val >> 32;
+    uint32_t lo = val, hi = val >> 32;
 
-        wrmsr(msr, lo, hi);
+    asm volatile ( "wrmsr" :: "a" (lo), "d" (hi), "c" (msr) );
 }
+#define wrmsrl(msr, val) wrmsr(msr, val)
 
 /* Non-serialising WRMSR, when available.  Falls back to a serialising WRMSR. */
 static inline void wrmsrns(uint32_t msr, uint64_t val)
@@ -150,7 +150,7 @@ static inline void wrmsr_tsc_aux(uint32_t val)
 
     if ( *this_tsc_aux != val )
     {
-        wrmsr(MSR_TSC_AUX, val, 0);
+        wrmsrns(MSR_TSC_AUX, val);
         *this_tsc_aux = val;
     }
 }

xen/arch/x86/nmi.c

@@ -218,16 +218,16 @@ void disable_lapic_nmi_watchdog(void)
         return;
     switch (boot_cpu_data.x86_vendor) {
     case X86_VENDOR_AMD:
-        wrmsr(MSR_K7_EVNTSEL0, 0, 0);
+        wrmsrns(MSR_K7_EVNTSEL0, 0);
         break;
     case X86_VENDOR_INTEL:
         switch (boot_cpu_data.x86) {
         case 6:
-            wrmsr(MSR_P6_EVNTSEL(0), 0, 0);
+            wrmsrns(MSR_P6_EVNTSEL(0), 0);
             break;
         case 15:
-            wrmsr(MSR_P4_IQ_CCCR0, 0, 0);
-            wrmsr(MSR_P4_CRU_ESCR0, 0, 0);
+            wrmsr(MSR_P4_IQ_CCCR0, 0);
+            wrmsr(MSR_P4_CRU_ESCR0, 0);
             break;
         }
         break;
@@ -282,7 +282,7 @@ static void clear_msr_range(unsigned int base, unsigned int n)
     unsigned int i;
 
     for (i = 0; i < n; i++)
-        wrmsr(base+i, 0, 0);
+        wrmsrns(base + i, 0);
 }
 
 static inline void write_watchdog_counter(const char *descr)
@@ -308,11 +308,11 @@ static void setup_k7_watchdog(void)
         | K7_EVNTSEL_USR
         | K7_NMI_EVENT;
 
-    wrmsr(MSR_K7_EVNTSEL0, evntsel, 0);
+    wrmsrns(MSR_K7_EVNTSEL0, evntsel);
     write_watchdog_counter("K7_PERFCTR0");
     apic_write(APIC_LVTPC, APIC_DM_NMI);
     evntsel |= K7_EVNTSEL_ENABLE;
-    wrmsr(MSR_K7_EVNTSEL0, evntsel, 0);
+    wrmsrns(MSR_K7_EVNTSEL0, evntsel);
 }
 
 static void setup_p6_watchdog(unsigned counter)
@@ -338,11 +338,11 @@ static void setup_p6_watchdog(unsigned counter)
         | P6_EVNTSEL_USR
         | counter;
 
-    wrmsr(MSR_P6_EVNTSEL(0), evntsel, 0);
+    wrmsrns(MSR_P6_EVNTSEL(0), evntsel);
     write_watchdog_counter("P6_PERFCTR0");
     apic_write(APIC_LVTPC, APIC_DM_NMI);
     evntsel |= P6_EVNTSEL0_ENABLE;
-    wrmsr(MSR_P6_EVNTSEL(0), evntsel, 0);
+    wrmsrns(MSR_P6_EVNTSEL(0), evntsel);
 }
 
 static void setup_p4_watchdog(void)

xen/arch/x86/oprofile/op_model_athlon.c

@@ -34,7 +34,7 @@
 #define MAX_COUNTERS FAM15H_NUM_COUNTERS
 
 #define CTR_READ(msr_content,msrs,c) do {rdmsrl(msrs->counters[(c)].addr, (msr_content));} while (0)
-#define CTR_WRITE(l,msrs,c) do {wrmsr(msrs->counters[(c)].addr, -(unsigned int)(l), -1);} while (0)
+#define CTR_WRITE(l,msrs,c) wrmsr(msrs->counters[(c)].addr, -(l))
 #define CTR_OVERFLOWED(n) (!((n) & (1ULL<<31)))
 
 #define CTRL_READ(msr_content,msrs,c) do {rdmsrl(msrs->controls[(c)].addr, (msr_content));} while (0)