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Merge branch kvm-arm64/nv-timer-improvements into kvmarm/next

Browse source 
* kvm-arm64/nv-timer-improvements:
  : Timer emulation improvements, courtesy of Marc Zyngier.
  :
  :  - Avoid re-arming an hrtimer for a guest timer that is already pending
  :
  :  - Only reload the affected timer context when emulating a sysreg access
  :    instead of both the virtual/physical timers.
  KVM: arm64: timers: Don't BUG() on unhandled timer trap
  KVM: arm64: Reduce overhead of trapped timer sysreg accesses
  KVM: arm64: Don't arm a hrtimer for an already pending timer

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
This commit is contained in:
Oliver Upton 2023-02-13 23:26:21 +00:00
commit 1b915210d9
2 changed files with 52 additions and 29 deletions
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77
arch/arm64/kvm/arch_timer.c
View file

@ -428,14 +428,17 @@ static void timer_emulate(struct arch_timer_context *ctx)
* scheduled for the future. If the timer cannot fire at all,
* then we also don't need a soft timer.
*/
if (!kvm_timer_irq_can_fire(ctx)) {
soft_timer_cancel(&ctx->hrtimer);
if (should_fire || !kvm_timer_irq_can_fire(ctx))
return;
}
soft_timer_start(&ctx->hrtimer, kvm_timer_compute_delta(ctx));
}
static void set_cntvoff(u64 cntvoff)
{
kvm_call_hyp(__kvm_timer_set_cntvoff, cntvoff);
}
static void timer_save_state(struct arch_timer_context *ctx)
{
struct arch_timer_cpu *timer = vcpu_timer(ctx->vcpu);
@ -459,6 +462,22 @@ static void timer_save_state(struct arch_timer_context *ctx)
write_sysreg_el0(0, SYS_CNTV_CTL);
isb();
/*
* The kernel may decide to run userspace after
* calling vcpu_put, so we reset cntvoff to 0 to
* ensure a consistent read between user accesses to
* the virtual counter and kernel access to the
* physical counter of non-VHE case.
*
* For VHE, the virtual counter uses a fixed virtual
* offset of zero, so no need to zero CNTVOFF_EL2
* register, but this is actually useful when switching
* between EL1/vEL2 with NV.
*
* Do it unconditionally, as this is either unavoidable
* or dirt cheap.
*/
set_cntvoff(0);
break;
case TIMER_PTIMER:
timer_set_ctl(ctx, read_sysreg_el0(SYS_CNTP_CTL));
@ -532,6 +551,7 @@ static void timer_restore_state(struct arch_timer_context *ctx)
switch (index) {
case TIMER_VTIMER:
set_cntvoff(timer_get_offset(ctx));
write_sysreg_el0(timer_get_cval(ctx), SYS_CNTV_CVAL);
isb();
write_sysreg_el0(timer_get_ctl(ctx), SYS_CNTV_CTL);
@ -552,11 +572,6 @@ static void timer_restore_state(struct arch_timer_context *ctx)
local_irq_restore(flags);
}
static void set_cntvoff(u64 cntvoff)
{
kvm_call_hyp(__kvm_timer_set_cntvoff, cntvoff);
}
static inline void set_timer_irq_phys_active(struct arch_timer_context *ctx, bool active)
{
int r;
@ -631,8 +646,6 @@ void kvm_timer_vcpu_load(struct kvm_vcpu *vcpu)
kvm_timer_vcpu_load_nogic(vcpu);
}
set_cntvoff(timer_get_offset(map.direct_vtimer));
kvm_timer_unblocking(vcpu);
timer_restore_state(map.direct_vtimer);
@ -688,15 +701,6 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
if (kvm_vcpu_is_blocking(vcpu))
kvm_timer_blocking(vcpu);
/*
* The kernel may decide to run userspace after calling vcpu_put, so
* we reset cntvoff to 0 to ensure a consistent read between user
* accesses to the virtual counter and kernel access to the physical
* counter of non-VHE case. For VHE, the virtual counter uses a fixed
* virtual offset of zero, so no need to zero CNTVOFF_EL2 register.
*/
set_cntvoff(0);
}
/*
@ -934,14 +938,22 @@ u64 kvm_arm_timer_read_sysreg(struct kvm_vcpu *vcpu,
enum kvm_arch_timers tmr,
enum kvm_arch_timer_regs treg)
{
struct arch_timer_context *timer;
struct timer_map map;
u64 val;
get_timer_map(vcpu, &map);
timer = vcpu_get_timer(vcpu, tmr);
if (timer == map.emul_ptimer)
return kvm_arm_timer_read(vcpu, timer, treg);
preempt_disable();
kvm_timer_vcpu_put(vcpu);
timer_save_state(timer);
val = kvm_arm_timer_read(vcpu, vcpu_get_timer(vcpu, tmr), treg);
val = kvm_arm_timer_read(vcpu, timer, treg);
kvm_timer_vcpu_load(vcpu);
timer_restore_state(timer);
preempt_enable();
return val;
@ -975,13 +987,22 @@ void kvm_arm_timer_write_sysreg(struct kvm_vcpu *vcpu,
enum kvm_arch_timer_regs treg,
u64 val)
{
preempt_disable();
kvm_timer_vcpu_put(vcpu);
struct arch_timer_context *timer;
struct timer_map map;
kvm_arm_timer_write(vcpu, vcpu_get_timer(vcpu, tmr), treg, val);
kvm_timer_vcpu_load(vcpu);
preempt_enable();
get_timer_map(vcpu, &map);
timer = vcpu_get_timer(vcpu, tmr);
if (timer == map.emul_ptimer) {
soft_timer_cancel(&timer->hrtimer);
kvm_arm_timer_write(vcpu, timer, treg, val);
timer_emulate(timer);
} else {
preempt_disable();
timer_save_state(timer);
kvm_arm_timer_write(vcpu, timer, treg, val);
timer_restore_state(timer);
preempt_enable();
}
}
static int timer_irq_set_vcpu_affinity(struct irq_data *d, void *vcpu)

4
arch/arm64/kvm/sys_regs.c
View file

@ -1122,7 +1122,9 @@ static bool access_arch_timer(struct kvm_vcpu *vcpu,
treg = TIMER_REG_CVAL;
break;
default:
BUG();
print_sys_reg_msg(p, "%s", "Unhandled trapped timer register");
kvm_inject_undefined(vcpu);
return false;
}
if (p->is_write)