[PATCH v3 02/41] x86/tsc: Add helper to register CPU and TSC freq calibration routines

[Sean Christopherson <seanjc@xxxxxxxxxx>]

Add a helper to register non-native, i.e. PV and CoCo, CPU and TSC
frequency calibration routines.  This will allow consolidating handling
of common TSC properties that are forced by hypervisor (PV routines),
and will also allow adding sanity checks to guard against overriding a
TSC calibration routine with a routine that is less robust/trusted.

Make the CPU calibration routine optional, as Xen (very sanely) doesn't
assume the CPU runs as the same frequency as the TSC.

Wrap the helper in an #ifdef to document that the kernel overrides
the native routines when running as a VM, and to guard against unwanted
usage.  Add a TODO to call out that AMD_MEM_ENCRYPT is a mess and doesn't
depend on HYPERVISOR_GUEST because it gates both guest and host code.

No functional change intended.

Reviewed-by: Michael Kelley <mhklinux@xxxxxxxxxxx>
Tested-by: Michael Kelley <mhklinux@xxxxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
 arch/x86/coco/sev/core.c       |  4 ++--
 arch/x86/include/asm/tsc.h     |  4 ++++
 arch/x86/kernel/cpu/acrn.c     |  4 ++--
 arch/x86/kernel/cpu/mshyperv.c |  3 +--
 arch/x86/kernel/cpu/vmware.c   |  4 ++--
 arch/x86/kernel/jailhouse.c    |  4 ++--
 arch/x86/kernel/kvmclock.c     |  4 ++--
 arch/x86/kernel/tsc.c          | 17 +++++++++++++++++
 arch/x86/xen/time.c            |  2 +-
 9 files changed, 33 insertions(+), 13 deletions(-)

diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index 7ed3da998489..d27cf8f8b025 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -2048,8 +2048,8 @@ void __init snp_secure_tsc_init(void)
 
        snp_tsc_freq_khz = SNP_SCALE_TSC_FREQ(tsc_freq_mhz * 1000, 
secrets->tsc_factor);
 
-       x86_platform.calibrate_cpu = securetsc_get_tsc_khz;
-       x86_platform.calibrate_tsc = securetsc_get_tsc_khz;
+       tsc_register_calibration_routines(securetsc_get_tsc_khz,
+                                         securetsc_get_tsc_khz);
 
        early_memunmap(mem, PAGE_SIZE);
 }
diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index 0c57fadc4a39..bae709f5f44d 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -94,6 +94,10 @@ extern int cpuid_get_tsc_freq(struct cpuid_tsc_info *info);
 
 extern void tsc_early_init(void);
 extern void tsc_init(void);
+#if defined(CONFIG_HYPERVISOR_GUEST) || defined(CONFIG_AMD_MEM_ENCRYPT)
+extern void tsc_register_calibration_routines(unsigned long 
(*calibrate_tsc)(void),
+                                             unsigned long 
(*calibrate_cpu)(void));
+#endif
 extern void mark_tsc_unstable(char *reason);
 extern int unsynchronized_tsc(void);
 extern int check_tsc_unstable(void);
diff --git a/arch/x86/kernel/cpu/acrn.c b/arch/x86/kernel/cpu/acrn.c
index 2c5b51aad91a..c1506cb87d8c 100644
--- a/arch/x86/kernel/cpu/acrn.c
+++ b/arch/x86/kernel/cpu/acrn.c
@@ -29,8 +29,8 @@ static void __init acrn_init_platform(void)
        /* Install system interrupt handler for ACRN hypervisor callback */
        sysvec_install(HYPERVISOR_CALLBACK_VECTOR, sysvec_acrn_hv_callback);
 
-       x86_platform.calibrate_tsc = acrn_get_tsc_khz;
-       x86_platform.calibrate_cpu = acrn_get_tsc_khz;
+       tsc_register_calibration_routines(acrn_get_tsc_khz,
+                                         acrn_get_tsc_khz);
 }
 
 static bool acrn_x2apic_available(void)
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 640e6b223c2d..8d2401be420c 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -573,8 +573,7 @@ static void __init ms_hyperv_init_platform(void)
 
        if (ms_hyperv.features & HV_ACCESS_FREQUENCY_MSRS &&
            ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) {
-               x86_platform.calibrate_tsc = hv_get_tsc_khz;
-               x86_platform.calibrate_cpu = hv_get_tsc_khz;
+               tsc_register_calibration_routines(hv_get_tsc_khz, 
hv_get_tsc_khz);
                setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
        }
 
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 34b73573b108..b88d9ca01202 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -419,8 +419,8 @@ static void __init vmware_platform_setup(void)
                }
 
                vmware_tsc_khz = tsc_khz;
-               x86_platform.calibrate_tsc = vmware_get_tsc_khz;
-               x86_platform.calibrate_cpu = vmware_get_tsc_khz;
+               tsc_register_calibration_routines(vmware_get_tsc_khz,
+                                                 vmware_get_tsc_khz);
 
 #ifdef CONFIG_X86_LOCAL_APIC
                /* Skip lapic calibration since we know the bus frequency. */
diff --git a/arch/x86/kernel/jailhouse.c b/arch/x86/kernel/jailhouse.c
index f58ce9220e0f..db8f31fdb480 100644
--- a/arch/x86/kernel/jailhouse.c
+++ b/arch/x86/kernel/jailhouse.c
@@ -210,8 +210,6 @@ static void __init jailhouse_init_platform(void)
        x86_init.mpparse.parse_smp_cfg          = jailhouse_parse_smp_config;
        x86_init.pci.arch_init                  = jailhouse_pci_arch_init;
 
-       x86_platform.calibrate_cpu              = jailhouse_get_tsc;
-       x86_platform.calibrate_tsc              = jailhouse_get_tsc;
        x86_platform.get_wallclock              = jailhouse_get_wallclock;
        x86_platform.legacy.rtc                 = 0;
        x86_platform.legacy.warm_reset          = 0;
@@ -221,6 +219,8 @@ static void __init jailhouse_init_platform(void)
 
        machine_ops.emergency_restart           = jailhouse_no_restart;
 
+       tsc_register_calibration_routines(jailhouse_get_tsc, jailhouse_get_tsc);
+
        while (pa_data) {
                mapping = early_memremap(pa_data, sizeof(header));
                memcpy(&header, mapping, sizeof(header));
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index b5991d53fc0e..e9e7394140dd 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -321,8 +321,8 @@ void __init kvmclock_init(void)
        flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
        kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
 
-       x86_platform.calibrate_tsc = kvm_get_tsc_khz;
-       x86_platform.calibrate_cpu = kvm_get_tsc_khz;
+       tsc_register_calibration_routines(kvm_get_tsc_khz, kvm_get_tsc_khz);
+
        x86_platform.get_wallclock = kvm_get_wallclock;
        x86_platform.set_wallclock = kvm_set_wallclock;
 #ifdef CONFIG_X86_LOCAL_APIC
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index f92236f40cbc..7e639c0a94a2 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1281,6 +1281,23 @@ static void __init check_system_tsc_reliable(void)
                tsc_disable_clocksource_watchdog();
 }
 
+/*
+ * TODO: Disentangle AMD_MEM_ENCRYPT and make SEV guest support depend on
+ *      HYPERVISOR_GUEST.
+ */
+#if defined(CONFIG_HYPERVISOR_GUEST) || defined(CONFIG_AMD_MEM_ENCRYPT)
+void tsc_register_calibration_routines(unsigned long (*calibrate_tsc)(void),
+                                      unsigned long (*calibrate_cpu)(void))
+{
+       if (WARN_ON_ONCE(!calibrate_tsc))
+               return;
+
+       x86_platform.calibrate_tsc = calibrate_tsc;
+       if (calibrate_cpu)
+               x86_platform.calibrate_cpu = calibrate_cpu;
+}
+#endif
+
 /*
  * Make an educated guess if the TSC is trustworthy and synchronized
  * over all CPUs.
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index d62c14334b35..3d3165eef821 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -569,7 +569,7 @@ static void __init xen_init_time_common(void)
        static_call_update(pv_steal_clock, xen_steal_clock);
        paravirt_set_sched_clock(xen_sched_clock);
 
-       x86_platform.calibrate_tsc = xen_tsc_khz;
+       tsc_register_calibration_routines(xen_tsc_khz, NULL);
        x86_platform.get_wallclock = xen_get_wallclock;
 }
 
-- 
2.54.0.563.g4f69b47b94-goog