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    SubjectRe: [RFC v2 10/10] KVM: arm/arm64: Emulate the EL1 phys timer register access
    Date
    On Fri, Jan 27 2017 at 01:05:00 AM, Jintack Lim <jintack@cs.columbia.edu> wrote:
    > Emulate read and write operations to CNTP_TVAL, CNTP_CVAL and CNTP_CTL.
    > Now VMs are able to use the EL1 physical timer.
    >
    > Signed-off-by: Jintack Lim <jintack@cs.columbia.edu>
    > ---
    > arch/arm64/kvm/sys_regs.c | 32 +++++++++++++++++++++++++++++---
    > include/kvm/arm_arch_timer.h | 2 ++
    > virt/kvm/arm/arch_timer.c | 2 +-
    > 3 files changed, 32 insertions(+), 4 deletions(-)
    >
    > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
    > index fd9e747..adf009f 100644
    > --- a/arch/arm64/kvm/sys_regs.c
    > +++ b/arch/arm64/kvm/sys_regs.c
    > @@ -824,7 +824,14 @@ static bool access_cntp_tval(struct kvm_vcpu *vcpu,
    > struct sys_reg_params *p,
    > const struct sys_reg_desc *r)
    > {
    > - kvm_inject_undefined(vcpu);
    > + struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
    > + u64 now = kvm_phys_timer_read();
    > +
    > + if (p->is_write)
    > + ptimer->cnt_cval = p->regval + now;
    > + else
    > + p->regval = ptimer->cnt_cval - now;
    > +
    > return true;
    > }
    >
    > @@ -832,7 +839,20 @@ static bool access_cntp_ctl(struct kvm_vcpu *vcpu,
    > struct sys_reg_params *p,
    > const struct sys_reg_desc *r)
    > {
    > - kvm_inject_undefined(vcpu);
    > + struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
    > +
    > + if (p->is_write) {
    > + /* ISTATUS bit is read-only */
    > + ptimer->cnt_ctl = p->regval & ~ARCH_TIMER_CTRL_IT_STAT;
    > + } else {
    > + u64 now = kvm_phys_timer_read();
    > +
    > + p->regval = ptimer->cnt_ctl;
    > + /* Set ISTATUS bit if it's expired */
    > + if (ptimer->cnt_cval <= now)
    > + p->regval |= ARCH_TIMER_CTRL_IT_STAT;
    > + }

    Shouldn't we take the ENABLE bit into account? The ARMv8 ARM version I
    have at hand (version h) seems to indicate that we should, but we should
    check with the latest and greatest...

    > +
    > return true;
    > }
    >
    > @@ -840,7 +860,13 @@ static bool access_cntp_cval(struct kvm_vcpu *vcpu,
    > struct sys_reg_params *p,
    > const struct sys_reg_desc *r)
    > {
    > - kvm_inject_undefined(vcpu);
    > + struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
    > +
    > + if (p->is_write)
    > + ptimer->cnt_cval = p->regval;
    > + else
    > + p->regval = ptimer->cnt_cval;
    > +
    > return true;
    > }
    >
    > diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
    > index a364593..fec99f2 100644
    > --- a/include/kvm/arm_arch_timer.h
    > +++ b/include/kvm/arm_arch_timer.h
    > @@ -74,6 +74,8 @@ bool kvm_timer_should_fire(struct kvm_vcpu *vcpu,
    > void kvm_timer_schedule(struct kvm_vcpu *vcpu);
    > void kvm_timer_unschedule(struct kvm_vcpu *vcpu);
    >
    > +u64 kvm_phys_timer_read(void);
    > +
    > void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu);
    >
    > void kvm_timer_init_vhe(void);
    > diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
    > index b366bb2..9eec063 100644
    > --- a/virt/kvm/arm/arch_timer.c
    > +++ b/virt/kvm/arm/arch_timer.c
    > @@ -40,7 +40,7 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
    > vcpu_vtimer(vcpu)->active_cleared_last = false;
    > }
    >
    > -static u64 kvm_phys_timer_read(void)
    > +u64 kvm_phys_timer_read(void)
    > {
    > return timecounter->cc->read(timecounter->cc);
    > }

    Thanks,

    M.
    --
    Jazz is not dead. It just smells funny.

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