[PATCH 4/5] x86/nmi: Check MSR_MISC_ENABLE for all Intel platforms

[Andrew Cooper <andrew.cooper3@citrix.com>]

Right now it's only checked in setup_p4_watchdog(), and not in
setup_p6_watchdog().

Perform the check in the common Intel path in
setup_apic_nmi_watchdog(), and pass misc_enable as a parameter into
setup_p4_watchdog() to aoid reading it twice.

Fixes: 0dfba864fbff ("NMI watchdog support in Xen.")
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <jbeulich@suse.com>
CC: Roger Pau Monné <roger@xenproject.org>
CC: Teddy Astie <teddy.astie@vates.tech>

I presume this bug went unnoticed because watchdog is off-by-default.
---
 xen/arch/x86/nmi.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/nmi.c b/xen/arch/x86/nmi.c
index d9d07870a333..a8b0d79c7cf2 100644
--- a/xen/arch/x86/nmi.c
+++ b/xen/arch/x86/nmi.c
@@ -295,14 +295,8 @@ static void setup_p6_watchdog(unsigned counter)
     wrmsrns(MSR_P6_EVNTSEL(0), evntsel);
 }
 
-static void setup_p4_watchdog(void)
+static void setup_p4_watchdog(uint64_t misc_enable)
 {
-    uint64_t misc_enable;
-
-    rdmsrl(MSR_IA32_MISC_ENABLE, misc_enable);
-    if ( !(misc_enable & MSR_IA32_MISC_ENABLE_PERF_AVAIL) )
-        return;
-
     nmi_perfctr_msr = MSR_P4_IQ_PERFCTR0;
     nmi_p4_cccr_val = P4_NMI_IQ_CCCR0;
     if ( boot_cpu_data.x86_num_siblings == 2 )
@@ -337,6 +331,8 @@ static void setup_p4_watchdog(void)
 
 void setup_apic_nmi_watchdog(void)
 {
+    uint64_t misc;
+
     if ( nmi_watchdog == NMI_NONE )
         return;
 
@@ -347,6 +343,14 @@ void setup_apic_nmi_watchdog(void)
         break;
 
     case X86_VENDOR_INTEL:
+        misc = rdmsr(MSR_IA32_MISC_ENABLE);
+
+        if ( !(misc & MSR_IA32_MISC_ENABLE_PERF_AVAIL) )
+        {
+            printk(XENLOG_WARNING "Intel Perfmon unavailable\n");
+            goto disable;
+        }
+
         switch ( boot_cpu_data.family )
         {
         case 6:
@@ -355,7 +359,7 @@ void setup_apic_nmi_watchdog(void)
                               : CORE_EVENT_CPU_CLOCKS_NOT_HALTED);
             break;
         case 15:
-            setup_p4_watchdog();
+            setup_p4_watchdog(misc);
             break;
         }
         break;
@@ -363,6 +367,7 @@ void setup_apic_nmi_watchdog(void)
 
     if ( nmi_perfctr_msr == 0 )
     {
+    disable:
         printk(XENLOG_WARNING "Failed to configure NMI watchdog\n");
         nmi_watchdog = NMI_NONE;
         return;
-- 
2.34.1