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KVM: PPC: Use exported tb_to_ns() function in decrementer emulation

PATCH Superseded Paul Mackerras 2 participants 3 messages Oct 19, 2018 – Oct 31, 2018

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Paul Mackerras

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#0 lore raw

PATCH 1/1 KVM: PPC: Use exported tb_to_ns() function in decrementer emulation

This changes the KVM code that emulates the decrementer function to do the conversion of decrementer values to time intervals in nanoseconds by calling the tb_to_ns() function exported by the powerpc timer code, in preference to open-coded arithmetic using values from the decrementer_clockevent struct. Similarly, the HV-KVM code that did the same conversion using arithmetic on tb_ticks_per_sec also now uses tb_to_ns().

Signed-off-by Paul Mackerras <[email protected]>
---
 arch/powerpc/kvm/book3s_hv.c | 3 +--
 arch/powerpc/kvm/emulate.c   | 6 ++----
 2 files changed, 3 insertions(+), 6 deletions(-)
arch/powerpc/kvm/book3s_hv.c +1 -2
index bf8def2..d65b961 100644
@@ -2337,8 +2337,7 @@ static void kvmppc_set_timer(struct kvm_vcpu *vcpu)
 		kvmppc_core_prepare_to_enter(vcpu);
 		return;
 	}
-	dec_nsec = (vcpu->arch.dec_expires - now) * NSEC_PER_SEC
-		   / tb_ticks_per_sec;
+	dec_nsec = tb_to_ns(vcpu->arch.dec_expires - now);
 	hrtimer_start(&vcpu->arch.dec_timer, dec_nsec, HRTIMER_MODE_REL);
 	vcpu->arch.timer_running = 1;
 }
arch/powerpc/kvm/emulate.c +2 -4
index fa888bf..7a7c348 100644
@@ -62,11 +62,9 @@ void kvmppc_emulate_dec(struct kvm_vcpu *vcpu)
 	dec_time = vcpu->arch.dec;
 	/*
 	 * Guest timebase ticks at the same frequency as host decrementer.
-	 * So use the host decrementer calculations for decrementer emulation.
+	 * So use the host timebase calculations for decrementer emulation.
 	 */
-	dec_time = dec_time << decrementer_clockevent.shift;
-	do_div(dec_time, decrementer_clockevent.mult);
-	dec_nsec = do_div(dec_time, NSEC_PER_SEC);
+	dec_nsec = tb_to_ns(dec_time);
 	hrtimer_start(&vcpu->arch.dec_timer,
 		ktime_set(dec_time, dec_nsec), HRTIMER_MODE_REL);
 	vcpu->arch.dec_jiffies = get_tb();
Signature · 1 line
2.7.4
author
#1 lore raw

PATCH v2 1/1 KVM: PPC: Use exported tb_to_ns() function in decrementer emulation

This changes the KVM code that emulates the decrementer function to do the conversion of decrementer values to time intervals in nanoseconds by calling the tb_to_ns() function exported by the powerpc timer code, in preference to open-coded arithmetic using values from the decrementer_clockevent struct. Similarly, the HV-KVM code that did the same conversion using arithmetic on tb_ticks_per_sec also now uses tb_to_ns().

Signed-off-by Paul Mackerras <[email protected]>

---
v2: don't delete the second do_div in kvmppc_emulate_dec(), we need it.

 arch/powerpc/kvm/book3s_hv.c | 3 +--
 arch/powerpc/kvm/emulate.c   | 7 +++----
 2 files changed, 4 insertions(+), 6 deletions(-)
arch/powerpc/kvm/book3s_hv.c +1 -2
index bf8def2..d65b961 100644
@@ -2337,8 +2337,7 @@ static void kvmppc_set_timer(struct kvm_vcpu *vcpu)
 		kvmppc_core_prepare_to_enter(vcpu);
 		return;
 	}
-	dec_nsec = (vcpu->arch.dec_expires - now) * NSEC_PER_SEC
-		   / tb_ticks_per_sec;
+	dec_nsec = tb_to_ns(vcpu->arch.dec_expires - now);
 	hrtimer_start(&vcpu->arch.dec_timer, dec_nsec, HRTIMER_MODE_REL);
 	vcpu->arch.timer_running = 1;
 }
arch/powerpc/kvm/emulate.c +3 -4
index fa888bf..9f5b8c0 100644
@@ -61,11 +61,10 @@ void kvmppc_emulate_dec(struct kvm_vcpu *vcpu)
 
 	dec_time = vcpu->arch.dec;
 	/*
-	 * Guest timebase ticks at the same frequency as host decrementer.
-	 * So use the host decrementer calculations for decrementer emulation.
+	 * Guest timebase ticks at the same frequency as host timebase.
+	 * So use the host timebase calculations for decrementer emulation.
 	 */
-	dec_time = dec_time << decrementer_clockevent.shift;
-	do_div(dec_time, decrementer_clockevent.mult);
+	dec_time = tb_to_ns(dec_time);
 	dec_nsec = do_div(dec_time, NSEC_PER_SEC);
 	hrtimer_start(&vcpu->arch.dec_timer,
 		ktime_set(dec_time, dec_nsec), HRTIMER_MODE_REL);
Signature · 1 line
2.7.4
Applied
#2 lore raw
Quoted 9 lines · Paul Mackerras

This changes the KVM code that emulates the decrementer function to do the conversion of decrementer values to time intervals in nanoseconds by calling the tb_to_ns() function exported by the powerpc timer code, in preference to open-coded arithmetic using values from the decrementer_clockevent struct. Similarly, the HV-KVM code that did the same conversion using arithmetic on tb_ticks_per_sec also now uses tb_to_ns().

Signed-off-by Paul Mackerras <[email protected]>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/c43befca86ae35cc82bd889484bd17

cheers