Commit a091fe60 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: x86: Grab lapic_timer in a local variable to cleanup periodic code 

Stash apic->lapic_timer in a local "ktimer" variable in
advance_periodic_target_expiration() to eliminate a few unaligned wraps,
and to make the code easier to read overall.

No functional change intended.

Link: https://patch.msgid.link/20251113205114.1647493-5-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 18ab3fc8

arch/x86/kvm/lapic.c

+8 −8
Original line number Diff line number Diff line
@@ -2126,6 +2126,7 @@ static bool set_target_expiration(struct kvm_lapic *apic, u32 count_reg) 


static void advance_periodic_target_expiration(struct kvm_lapic *apic)

{

	struct kvm_timer *ktimer = &apic->lapic_timer;

	ktime_t now = ktime_get();

	u64 tscl = rdtsc();

	ktime_t delta;
@@ -2137,9 +2138,8 @@ static void advance_periodic_target_expiration(struct kvm_lapic *apic) 
	 * over time as differences in the periods accumulate, e.g. due to

	 * differences in the underlying clocks or numerical approximation errors.

	 */

	apic->lapic_timer.target_expiration =

		ktime_add_ns(apic->lapic_timer.target_expiration,

				apic->lapic_timer.period);

	ktimer->target_expiration = ktime_add_ns(ktimer->target_expiration,

						 ktimer->period);



	/*

	 * If the new expiration is in the past, e.g. because userspace stopped
@@ -2150,16 +2150,16 @@ static void advance_periodic_target_expiration(struct kvm_lapic *apic) 
	 * past will do nothing more than waste host cycles, and can even lead

	 * to a hard lockup in extreme cases.

	 */

	if (ktime_before(apic->lapic_timer.target_expiration, now))

		apic->lapic_timer.target_expiration = now;

	if (ktime_before(ktimer->target_expiration, now))

		ktimer->target_expiration = now;



	/*

	 * Note, ensuring the expiration isn't in the past also prevents delta

	 * from going negative, which could cause the TSC deadline to become

	 * excessively large due to it an unsigned value.

	 */

	delta = ktime_sub(apic->lapic_timer.target_expiration, now);

	apic->lapic_timer.tscdeadline = kvm_read_l1_tsc(apic->vcpu, tscl) +

	delta = ktime_sub(ktimer->target_expiration, now);

	ktimer->tscdeadline = kvm_read_l1_tsc(apic->vcpu, tscl) +

			      nsec_to_cycles(apic->vcpu, delta);

}