-----Original Message-----
From: Marc Zyngier <maz@kernel.org>
Sent: Wednesday, August 19, 2020 6:39 PM
To: Jianyong Wu <redacted>
Cc: Paolo Bonzini <pbonzini@redhat.com>; Peng Hao
[off-list ref]; kernel-team@android.com; kvm@vger.kernel.org;
Will Deacon [off-list ref]; Catalin Marinas [off-list ref];
Alexander Graf [off-list ref]; 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 11:18, Jianyong Wu wrote:

quoted

quoted

-----Original Message-----
From: Marc Zyngier <maz@kernel.org>
Sent: Wednesday, August 19, 2020 6:00 PM
To: Jianyong Wu <redacted>
Cc: Paolo Bonzini <pbonzini@redhat.com>; Peng Hao
[off-list ref]; kernel-team@android.com;
kvm@vger.kernel.org; Will Deacon [off-list ref]; Catalin Marinas
[off-list ref]; Alexander Graf [off-list ref];
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:

quoted

Hi Marc,

-----Original Message-----
From: kvmarm-bounces@lists.cs.columbia.edu
[off-list ref] On Behalf Of Marc Zyngier
Sent: Thursday, August 6, 2020 1:57 AM
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peng Hao <redacted>; kernel-team@android.com;
kvm@vger.kernel.org; Will Deacon [off-list ref]; Catalin Marinas
[off-list ref]; Alexander Graf [off-list ref];
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.

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...

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