[PATCH 47/56] KVM: arm64: timers: Move timer registers to the sys_regs file

[Jianyong Wu]

> -----Original Message-----
> From: Marc Zyngier <maz at kernel.org>
> Sent: Wednesday, August 19, 2020 6:39 PM
> To: Jianyong Wu <Jianyong.Wu at arm.com>
> Cc: Paolo Bonzini <pbonzini at redhat.com>; Peng Hao
> <richard.peng at oppo.com>; kernel-team at android.com; kvm at vger.kernel.org;
> Will Deacon <will at kernel.org>; Catalin Marinas <Catalin.Marinas at arm.com>;
> Alexander Graf <graf at amazon.com>; kvmarm at lists.cs.columbia.edu; linux-
> arm-kernel at lists.infradead.org
> Subject: Re: [PATCH 47/56] KVM: arm64: timers: Move timer registers to the
> sys_regs file
> 
> On 2020-08-19 11:18, Jianyong Wu wrote:
> >> -----Original Message-----
> >> From: Marc Zyngier <maz at kernel.org>
> >> Sent: Wednesday, August 19, 2020 6:00 PM
> >> To: Jianyong Wu <Jianyong.Wu at arm.com>
> >> Cc: Paolo Bonzini <pbonzini at redhat.com>; Peng Hao
> >> <richard.peng at oppo.com>; kernel-team at android.com;
> >> kvm at vger.kernel.org; Will Deacon <will at kernel.org>; Catalin Marinas
> >> <Catalin.Marinas at arm.com>; Alexander Graf <graf at amazon.com>;
> >> kvmarm at lists.cs.columbia.edu; linux-arm-kernel at lists.infradead.org
> >> Subject: Re: [PATCH 47/56] KVM: arm64: timers: Move timer registers
> >> to the sys_regs file
> >>
> >> On 2020-08-19 10:24, Jianyong Wu wrote:
> >> > Hi Marc,
> >> >
> >> > -----Original Message-----
> >> > From: kvmarm-bounces at lists.cs.columbia.edu
> >> > <kvmarm-bounces at lists.cs.columbia.edu> On Behalf Of Marc Zyngier
> >> > Sent: Thursday, August 6, 2020 1:57 AM
> >> > To: Paolo Bonzini <pbonzini at redhat.com>
> >> > Cc: Peng Hao <richard.peng at oppo.com>; kernel-team at android.com;
> >> > kvm at vger.kernel.org; Will Deacon <will at kernel.org>; Catalin Marinas
> >> > <Catalin.Marinas at arm.com>; Alexander Graf <graf at amazon.com>;
> >> > kvmarm at lists.cs.columbia.edu; linux-arm-kernel at lists.infradead.org
> >> > Subject: [PATCH 47/56] KVM: arm64: timers: Move timer registers to
> >> > the sys_regs file
> >> >
> >> > Move the timer gsisters to the sysreg file. This will further help
> >> > when they are directly changed by a nesting hypervisor in the VNCR
> >> > page.
> >> >
> >> > This requires moving the initialisation of the timer struct so that
> >> > some of the helpers (such as arch_timer_ctx_index) can work
> >> > correctly at an early stage.
> >> >
> >> > Signed-off-by: Marc Zyngier <maz at kernel.org>
> >> > ---
> >> >  arch/arm64/include/asm/kvm_host.h |   6 ++
> >> >  arch/arm64/kvm/arch_timer.c       | 155 +++++++++++++++++++++++-------
> >> >  arch/arm64/kvm/trace_arm.h        |   8 +-
> >> >  include/kvm/arm_arch_timer.h      |  11 +--
> >> >  4 files changed, 136 insertions(+), 44 deletions(-)
> >> >
> >> > +static u64 timer_get_offset(struct arch_timer_context *ctxt) {
> >> > +	struct kvm_vcpu *vcpu = ctxt->vcpu;
> >> > +
> >> > +	switch(arch_timer_ctx_index(ctxt)) {
> >> > +	case TIMER_VTIMER:
> >> > +		return __vcpu_sys_reg(vcpu, CNTVOFF_EL2);
> >> > +	default:
> >> > +		return 0;
> >> > +	}
> >> > +}
> >> > +
> >> > Can I export this helper? As in my ptp_kvm implementation I need
> >> > get VCNT offset value separately not just give me a result of VCNT.
> >>
> >> Sorry, you need to give me a bit more context. What do you need the
> >> offset for exactly?
> >
> > Yeah,
> > In my ptp_kvm implementation, I need acquire wall time and counter
> > cycle in the same time in host. After get host counter cycle, I need
> > subtract it by VCNT offset to obtain VCNT. See
> > https://lkml.org/lkml/2020/6/19/441
> > https://lkml.org/lkml/2020/6/19/441
> > But now I can't get the VCNT offset easily like before using "
> > vcpu_vtimer(vcpu)->cntvoff" and I can't use the helper like
> > "kvm_arm_timer_read" as I need acquire the counter cycle in the same
> > time with the host wall time.
> 
> I must be missing something. CNTVOFF_EL2 is now implemented as a standard
> system register, and has the same visibility as any other vcpu sysreg.
> 
> Why doesn't vcpu_read_sys_reg(vcpu, CNTVOFF_EL2) work for you?

Maybe it serves me, let me try it, thanks.

Thanks
Jianyong
> 
>          M.
> --
> Jazz is not dead. It just smells funny...