From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Ilias Stamatis <ilstam@amazon.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
mlevitsk@redhat.com, vkuznets@redhat.com, wanpengli@tencent.com,
jmattson@google.com, joro@8bytes.org, zamsden@gmail.com,
mtosatti@redhat.com, dwmw@amazon.co.uk
Subject: Re: [PATCH v3 04/12] KVM: X86: Add a ratio parameter to kvm_scale_tsc()
Date: Mon, 24 May 2021 15:48:18 +0000 [thread overview]
Message-ID: <YKvKwpRP6UcftcnQ@google.com> (raw)
In-Reply-To: <cba90aa4-0665-a2d5-29e0-133e0aa45ad2@redhat.com>
On Mon, May 24, 2021, Paolo Bonzini wrote:
> On 21/05/21 12:24, Ilias Stamatis wrote:
> > @@ -3537,10 +3539,14 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> > * return L1's TSC value to ensure backwards-compatible
> > * behavior for migration.
> > */
> > - u64 tsc_offset = msr_info->host_initiated ? vcpu->arch.l1_tsc_offset :
> > - vcpu->arch.tsc_offset;
> > -
> > - msr_info->data = kvm_scale_tsc(vcpu, rdtsc()) + tsc_offset;
> > + if (msr_info->host_initiated)
> > + msr_info->data = kvm_scale_tsc(
> > + vcpu, rdtsc(), vcpu->arch.l1_tsc_scaling_ratio
> > + ) + vcpu->arch.l1_tsc_offset;
>
> Better indentation:
>
> msr_info->data = vcpu->arch.l1_tsc_offset +
> kvm_scale_tsc(vcpu, rdtsc(),
I like this more, but it's still a bit ugly.
> vcpu->arch.tsc_scaling_ratio);
Wrong pairing of ratio and offset (not necessarily what you queued, obviously).
>
> Same below.
Alternatively, what about something like this?
u64 offset, ratio;
if (msr_info->host_initiated) {
offset = vcpu->arch.l1_tsc_offset;
ratio = vcpu->arch.l1_tsc_scaling_ratio;
} else {
offset = vcpu->arch.tsc_offset;
ratio = vcpu->arch.tsc_scaling_ratio;
}
msr_info->data = kvm_scale_tsc(vcpu, rdtsc(), ratio) + offset;
or an option that would require additional refactoring:
struct kvm_guest_tsc *tsc;
tsc = msr_info->host_initiated ? &vcpu->arch.l1_tsc :
&vcpu->arch.current_tsc;
msr_info->data = tsc->offset +
kvm_scale_tsc(vcpu, rdtsc(), tsc->scaling_ratio);
>
> Paolo
>
> > + else
> > + msr_info->data = kvm_scale_tsc(
> > + vcpu, rdtsc(), vcpu->arch.tsc_scaling_ratio
> > + ) + vcpu->arch.tsc_offset;
> > break;
> > }
> > case MSR_MTRRcap:
> >
>
next prev parent reply other threads:[~2021-05-24 16:09 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-21 10:24 [PATCH v3 00/12] KVM: Implement nested TSC scaling Ilias Stamatis
2021-05-21 10:24 ` [PATCH v3 01/12] math64.h: Add mul_s64_u64_shr() Ilias Stamatis
2021-05-24 17:49 ` Maxim Levitsky
2021-05-21 10:24 ` [PATCH v3 02/12] KVM: X86: Store L1's TSC scaling ratio in 'struct kvm_vcpu_arch' Ilias Stamatis
2021-05-24 17:49 ` Maxim Levitsky
2021-05-21 10:24 ` [PATCH v3 03/12] KVM: X86: Rename kvm_compute_tsc_offset() to kvm_compute_tsc_offset_l1() Ilias Stamatis
2021-05-24 14:21 ` Paolo Bonzini
2021-05-24 17:49 ` Maxim Levitsky
2021-05-21 10:24 ` [PATCH v3 04/12] KVM: X86: Add a ratio parameter to kvm_scale_tsc() Ilias Stamatis
2021-05-24 14:23 ` Paolo Bonzini
2021-05-24 15:48 ` Sean Christopherson [this message]
2021-05-24 15:56 ` Paolo Bonzini
2021-05-24 17:50 ` Maxim Levitsky
2021-05-21 10:24 ` [PATCH v3 05/12] KVM: VMX: Add a TSC multiplier field in VMCS12 Ilias Stamatis
2021-05-21 10:24 ` [PATCH v3 06/12] KVM: X86: Add functions for retrieving L2 TSC fields from common code Ilias Stamatis
2021-05-24 17:50 ` Maxim Levitsky
2021-05-21 10:24 ` [PATCH v3 07/12] KVM: X86: Add functions that calculate L2's TSC offset and multiplier Ilias Stamatis
2021-05-24 17:51 ` Maxim Levitsky
2021-05-21 10:24 ` [PATCH v3 08/12] KVM: X86: Move write_l1_tsc_offset() logic to common code and rename it Ilias Stamatis
2021-05-24 17:51 ` Maxim Levitsky
2021-05-21 10:24 ` [PATCH v3 09/12] KVM: VMX: Remove vmx->current_tsc_ratio and decache_tsc_multiplier() Ilias Stamatis
2021-05-24 17:53 ` Maxim Levitsky
2021-05-24 18:44 ` Sean Christopherson
2021-05-25 10:41 ` Stamatis, Ilias
2021-05-25 15:58 ` Sean Christopherson
2021-05-25 16:15 ` Paolo Bonzini
2021-05-25 16:34 ` Sean Christopherson
2021-05-25 17:34 ` Paolo Bonzini
2021-05-25 18:21 ` Sean Christopherson
2021-05-25 18:52 ` Stamatis, Ilias
2021-05-25 19:25 ` Stamatis, Ilias
2021-05-25 23:35 ` Sean Christopherson
2021-05-21 10:24 ` [PATCH v3 10/12] KVM: VMX: Set the TSC offset and multiplier on nested entry and exit Ilias Stamatis
2021-05-24 17:54 ` Maxim Levitsky
2021-05-25 16:05 ` Sean Christopherson
2021-05-21 10:24 ` [PATCH v3 11/12] KVM: VMX: Expose TSC scaling to L2 Ilias Stamatis
2021-05-21 10:24 ` [PATCH v3 12/12] KVM: selftests: x86: Add vmx_nested_tsc_scaling_test Ilias Stamatis
2021-05-24 17:55 ` Maxim Levitsky
2021-05-24 15:37 ` [PATCH v3 00/12] KVM: Implement nested TSC scaling Paolo Bonzini
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