[PATCH v8 14/17] KVM: x86: Make master clock logic in guest PV clock updates 64-bit only

[Sean Christopherson]

Wrap kvm_guest_time_update()'s entire use_master_clock block in #ifdef
CONFIG_X86_64 and providing a hardcoded-to-false variable for the 32-bit
path, as use_master_clock is never true on 32-bit (host_tsc_clocksource is
only set under CONFIG_X86_64)

Keep the local "ka" variable outside of the 64-bit-only code as it's also
used for Xen code, but tag it as potentially unused since it's not used on
32-bit kernels without Xen emulation.

For all intents and purposes, no functional change intended.

Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
 arch/x86/kvm/x86.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 63702be799cc..070a12535788 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1796,22 +1796,21 @@ static void kvm_setup_guest_pvclock(struct pvclock_vcpu_time_info *ref_hv_clock,
 
 int kvm_guest_time_update(struct kvm_vcpu *v)
 {
+	struct kvm_arch *ka __maybe_unused = &v->kvm->arch;
 	struct pvclock_vcpu_time_info hv_clock = {};
 	u64 tgt_tsc_hz;
-	unsigned seq;
 	struct kvm_vcpu_arch *vcpu = &v->arch;
-	struct kvm_arch *ka = &v->kvm->arch;
 	s64 kernel_ns;
 	u64 tsc_timestamp, host_tsc;
+
+	/*
+	 * If the host uses TSC clock, then passthrough TSC as stable
+	 * to the guest.
+	 */
+#ifdef CONFIG_X86_64
 	bool use_master_clock;
+	unsigned int seq;
 
-	kernel_ns = 0;
-	host_tsc = 0;
-
-	/*
-	 * If the host uses TSC clock, then passthrough TSC as stable
-	 * to the guest.
-	 */
 	do {
 		seq = read_seqcount_begin(&ka->pvclock_sc);
 		use_master_clock = ka->use_master_clock;
@@ -1820,7 +1819,9 @@ int kvm_guest_time_update(struct kvm_vcpu *v)
 			kernel_ns = ka->master_kernel_ns;
 		}
 	} while (read_seqcount_retry(&ka->pvclock_sc, seq));
-
+#else
+	const bool use_master_clock = false;
+#endif
 	/*
 	 * Ensure reading the TSC+frequency pair is done on the same CPU.  When
 	 * NOT using the master clock, the TSC frequency may vary between CPUs.
-- 
2.55.0.571.g244d577d93-goog