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Subject[PATCH RFC 1/3] RISC-V: KVM: Change the method of calculating cycles to nanoseconds
Date
Because we will introduce the dynamic guest frequency later, we
can't use the fixed mult and shift to calculate nanoseconds.

Signed-off-by: Yifei Jiang <jiangyifei@huawei.com>
Signed-off-by: Yipeng Yin <yinyipeng1@huawei.com>
---
arch/riscv/include/asm/kvm_vcpu_timer.h | 3 ---
arch/riscv/kvm/vcpu_timer.c | 3 +--
2 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/arch/riscv/include/asm/kvm_vcpu_timer.h b/arch/riscv/include/asm/kvm_vcpu_timer.h
index 375281eb49e0..87e00d878999 100644
--- a/arch/riscv/include/asm/kvm_vcpu_timer.h
+++ b/arch/riscv/include/asm/kvm_vcpu_timer.h
@@ -12,9 +12,6 @@
#include <linux/hrtimer.h>

struct kvm_guest_timer {
- /* Mult & Shift values to get nanoseconds from cycles */
- u32 nsec_mult;
- u32 nsec_shift;
/* Time delta value */
u64 time_delta;
};
diff --git a/arch/riscv/kvm/vcpu_timer.c b/arch/riscv/kvm/vcpu_timer.c
index ddd0ce727b83..f6b35180199a 100644
--- a/arch/riscv/kvm/vcpu_timer.c
+++ b/arch/riscv/kvm/vcpu_timer.c
@@ -33,7 +33,7 @@ static u64 kvm_riscv_delta_cycles2ns(u64 cycles,
cycles_delta = cycles - cycles_now;
else
cycles_delta = 0;
- delta_ns = (cycles_delta * gt->nsec_mult) >> gt->nsec_shift;
+ delta_ns = mul_u64_u64_div_u64(cycles_delta, NSEC_PER_SEC, riscv_timebase);
local_irq_restore(flags);

return delta_ns;
@@ -218,7 +218,6 @@ int kvm_riscv_guest_timer_init(struct kvm *kvm)
{
struct kvm_guest_timer *gt = &kvm->arch.timer;

- riscv_cs_get_mult_shift(&gt->nsec_mult, &gt->nsec_shift);
gt->time_delta = -get_cycles64();

return 0;
--
2.19.1
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