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From: Sean Christopherson <seanjc@google.com>
To: Ilias Stamatis <ilstam@amazon.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	pbonzini@redhat.com, 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 v2 08/10] KVM: VMX: Set the TSC offset and multiplier on nested entry and exit
Date: Wed, 19 May 2021 00:07:56 +0000	[thread overview]
Message-ID: <YKRW3EF5NHBlJEOn@google.com> (raw)
In-Reply-To: <20210512150945.4591-9-ilstam@amazon.com>

On Wed, May 12, 2021, Ilias Stamatis wrote:
> Now that nested TSC scaling is supported we need to calculate the
> correct 02 values for both the offset and the multiplier using the
> corresponding functions. On L2's exit the L1 values are restored.
> 
> Signed-off-by: Ilias Stamatis <ilstam@amazon.com>
> ---
>  arch/x86/kvm/vmx/nested.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 6058a65a6ede..f1dff1ebaccb 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -3354,8 +3354,9 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
>  	}
>  
>  	enter_guest_mode(vcpu);
> -	if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETTING)
> -		vcpu->arch.tsc_offset += vmcs12->tsc_offset;
> +
> +	kvm_set_02_tsc_offset(vcpu);
> +	kvm_set_02_tsc_multiplier(vcpu);

Please move this code into prepare_vmcs02() to co-locate it with the relevant
vmcs02 logic.  If there's something in prepare_vmcs02() that consumes
vcpu->arch.tsc_offset() other than the obvious VMWRITE, I vote to move things
around to fix that rather than create this weird split.

>  	if (prepare_vmcs02(vcpu, vmcs12, &entry_failure_code)) {
>  		exit_reason.basic = EXIT_REASON_INVALID_STATE;
> @@ -4463,8 +4464,12 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,
>  	if (nested_cpu_has_preemption_timer(vmcs12))
>  		hrtimer_cancel(&to_vmx(vcpu)->nested.preemption_timer);
>  
> -	if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETTING)
> -		vcpu->arch.tsc_offset -= vmcs12->tsc_offset;
> +	if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETTING) {
> +		vcpu->arch.tsc_offset = vcpu->arch.l1_tsc_offset;
> +
> +		if (vmcs12->secondary_vm_exec_control & SECONDARY_EXEC_TSC_SCALING)
> +			vcpu->arch.tsc_scaling_ratio = vcpu->arch.l1_tsc_scaling_ratio;
> +	}
>  
>  	if (likely(!vmx->fail)) {
>  		sync_vmcs02_to_vmcs12(vcpu, vmcs12);
> -- 
> 2.17.1
> 

  reply	other threads:[~2021-05-19  0:08 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-12 15:09 [PATCH v2 00/10] KVM: Implement nested TSC scaling Ilias Stamatis
2021-05-12 15:09 ` [PATCH v2 01/10] math64.h: Add mul_s64_u64_shr() Ilias Stamatis
2021-05-18 22:36   ` Sean Christopherson
2021-05-12 15:09 ` [PATCH v2 02/10] KVM: X86: Store L1's TSC scaling ratio in 'struct kvm_vcpu_arch' Ilias Stamatis
2021-05-18 22:52   ` Sean Christopherson
2021-05-19  8:54     ` Stamatis, Ilias
2021-05-12 15:09 ` [PATCH v2 03/10] KVM: X86: Add kvm_scale_tsc_l1() and kvm_compute_tsc_offset_l1() Ilias Stamatis
2021-05-18 23:04   ` Sean Christopherson
2021-05-19  9:02     ` Stamatis, Ilias
2021-05-19 15:40       ` Sean Christopherson
2021-05-20 18:27         ` Stamatis, Ilias
2021-05-12 15:09 ` [PATCH v2 04/10] KVM: VMX: Add a TSC multiplier field in VMCS12 Ilias Stamatis
2021-05-12 15:09 ` [PATCH v2 05/10] KVM: X86: Add functions for retrieving L2 TSC fields from common code Ilias Stamatis
2021-05-12 15:09 ` [PATCH v2 06/10] KVM: X86: Add functions that calculate the 02 TSC offset and multiplier Ilias Stamatis
2021-05-18 23:21   ` Sean Christopherson
2021-05-19 10:15     ` Stamatis, Ilias
2021-05-12 15:09 ` [PATCH v2 07/10] KVM: X86: Move write_l1_tsc_offset() logic to common code and rename it Ilias Stamatis
2021-05-19  0:05   ` Sean Christopherson
2021-05-19 11:45     ` Stamatis, Ilias
2021-05-19 15:49       ` Sean Christopherson
2021-05-12 15:09 ` [PATCH v2 08/10] KVM: VMX: Set the TSC offset and multiplier on nested entry and exit Ilias Stamatis
2021-05-19  0:07   ` Sean Christopherson [this message]
2021-05-19 11:55     ` Stamatis, Ilias
2021-05-12 15:09 ` [PATCH v2 09/10] KVM: VMX: Expose TSC scaling to L2 Ilias Stamatis
2021-05-12 15:09 ` [PATCH v2 10/10] KVM: selftests: x86: Add vmx_nested_tsc_scaling_test Ilias Stamatis

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