x86/vmware: Read tsc_khz only once at boot time

Re-factor the vmware platform setup code to query the hypervisor for tsc
frequency only once during boot. Since the VMware hypervisor guarantees
constant TSC, calibrate_tsc now uses the saved value.

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Acked-by: Alok N Kataria <akataria@vmware.com>
Cc: virtualization@lists.linux-foundation.org
Link: http://lkml.kernel.org/r/20161020050211.GA25304@amakhalov-virtual-machine
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 81160578b91ac9a053bf5a5f172ea2fb6da1c241..4e34da4be297a02a7ac9d1be1cf7a5c20b7ac9ea 100644 (file)
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -47,6 +47,8 @@
                        "2"(VMWARE_HYPERVISOR_PORT), "3"(UINT_MAX) :    \
                        "memory");
 
+static unsigned long vmware_tsc_khz __ro_after_init;
+
 static inline int __vmware_platform(void)
 {
        uint32_t eax, ebx, ecx, edx;
@@ -56,35 +58,32 @@ static inline int __vmware_platform(void)
 
 static unsigned long vmware_get_tsc_khz(void)
 {
-       uint64_t tsc_hz, lpj;
-       uint32_t eax, ebx, ecx, edx;
-
-       VMWARE_PORT(GETHZ, eax, ebx, ecx, edx);
-
-       tsc_hz = eax | (((uint64_t)ebx) << 32);
-       do_div(tsc_hz, 1000);
-       BUG_ON(tsc_hz >> 32);
-       pr_info("TSC freq read from hypervisor : %lu.%03lu MHz\n",
-                        (unsigned long) tsc_hz / 1000,
-                        (unsigned long) tsc_hz % 1000);
-
-       if (!preset_lpj) {
-               lpj = ((u64)tsc_hz * 1000);
-               do_div(lpj, HZ);
-               preset_lpj = lpj;
-       }
-
-       return tsc_hz;
+       return vmware_tsc_khz;
 }
 
 static void __init vmware_platform_setup(void)
 {
        uint32_t eax, ebx, ecx, edx;
+       uint64_t lpj, tsc_khz;
 
        VMWARE_PORT(GETHZ, eax, ebx, ecx, edx);
 
        if (ebx != UINT_MAX) {
+               lpj = tsc_khz = eax | (((uint64_t)ebx) << 32);
+               do_div(tsc_khz, 1000);
+               WARN_ON(tsc_khz >> 32);
+               pr_info("TSC freq read from hypervisor : %lu.%03lu MHz\n",
+                       (unsigned long) tsc_khz / 1000,
+                       (unsigned long) tsc_khz % 1000);
+
+               if (!preset_lpj) {
+                       do_div(lpj, HZ);
+                       preset_lpj = lpj;
+               }
+
+               vmware_tsc_khz = tsc_khz;
                x86_platform.calibrate_tsc = vmware_get_tsc_khz;
+
 #ifdef CONFIG_X86_LOCAL_APIC
                /* Skip lapic calibration since we know the bus frequency. */
                lapic_timer_frequency = ecx / HZ;