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

From: Jianyong Wu <Jianyong.Wu@arm.com>
To: Marc Zyngier <maz@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Peng Hao <richard.peng@oppo.com>,
	"kernel-team@android.com" <kernel-team@android.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	Will Deacon <will@kernel.org>,
	Catalin Marinas <Catalin.Marinas@arm.com>,
	Alexander Graf <graf@amazon.com>,
	"kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>
Subject: RE: [PATCH 47/56] KVM: arm64: timers: Move timer registers to the sys_regs file
Date: Wed, 19 Aug 2020 10:18:18 +0000	[thread overview]
Message-ID: <HE1PR0802MB25552F2502B47554C6B53CADF45D0@HE1PR0802MB2555.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <551eac52dcd3b19ae6db45dd6f6e168b@kernel.org>

> -----Original Message-----
> From: Marc Zyngier <maz@kernel.org>
> Sent: Wednesday, August 19, 2020 6:00 PM
> To: Jianyong Wu <Jianyong.Wu@arm.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>; Peng Hao
> <richard.peng@oppo.com>; kernel-team@android.com;
> kvm@vger.kernel.org; Will Deacon <will@kernel.org>; Catalin Marinas
> <Catalin.Marinas@arm.com>; Alexander Graf <graf@amazon.com>;
> kvmarm@lists.cs.columbia.edu; linux-arm-kernel@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@lists.cs.columbia.edu
> > <kvmarm-bounces@lists.cs.columbia.edu> On Behalf Of Marc Zyngier
> > Sent: Thursday, August 6, 2020 1:57 AM
> > To: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: Peng Hao <richard.peng@oppo.com>; kernel-team@android.com;
> > kvm@vger.kernel.org; Will Deacon <will@kernel.org>; Catalin Marinas
> > <Catalin.Marinas@arm.com>; Alexander Graf <graf@amazon.com>;
> > kvmarm@lists.cs.columbia.edu; linux-arm-kernel@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@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.

Thanks
Jianyong

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