From: Maxim Levitsky <mlevitsk@redhat.com>
To: Ilias Stamatis <ilstam@amazon.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
pbonzini@redhat.com
Cc: seanjc@google.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 07/12] KVM: X86: Add functions that calculate L2's TSC offset and multiplier
Date: Mon, 24 May 2021 20:51:09 +0300 [thread overview]
Message-ID: <1110a7a9079031d9148142fe00356bf3a855258f.camel@redhat.com> (raw)
In-Reply-To: <20210521102449.21505-8-ilstam@amazon.com>
On Fri, 2021-05-21 at 11:24 +0100, Ilias Stamatis wrote:
> When L2 is entered we need to "merge" the TSC multiplier and TSC offset
> values of 01 and 12 together.
>
> The merging is done using the following equations:
> offset_02 = ((offset_01 * mult_12) >> shift_bits) + offset_12
> mult_02 = (mult_01 * mult_12) >> shift_bits
>
> Where shift_bits is kvm_tsc_scaling_ratio_frac_bits.
>
> Signed-off-by: Ilias Stamatis <ilstam@amazon.com>
> ---
> arch/x86/include/asm/kvm_host.h | 2 ++
> arch/x86/kvm/x86.c | 25 +++++++++++++++++++++++++
> 2 files changed, 27 insertions(+)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 0f2cf5d1240c..aaf756442ed1 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1792,6 +1792,8 @@ static inline bool kvm_is_supported_user_return_msr(u32 msr)
>
> u64 kvm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc, u64 ratio);
> u64 kvm_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc);
> +u64 kvm_calc_nested_tsc_offset(u64 l1_offset, u64 l2_offset, u64 l2_multiplier);
> +u64 kvm_calc_nested_tsc_multiplier(u64 l1_multiplier, u64 l2_multiplier);
>
> unsigned long kvm_get_linear_rip(struct kvm_vcpu *vcpu);
> bool kvm_is_linear_rip(struct kvm_vcpu *vcpu, unsigned long linear_rip);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index fdcb4f46a003..04abaacb9cfc 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2334,6 +2334,31 @@ u64 kvm_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc)
> }
> EXPORT_SYMBOL_GPL(kvm_read_l1_tsc);
>
> +u64 kvm_calc_nested_tsc_offset(u64 l1_offset, u64 l2_offset, u64 l2_multiplier)
> +{
> + u64 nested_offset;
> +
> + if (l2_multiplier == kvm_default_tsc_scaling_ratio)
> + nested_offset = l1_offset;
> + else
> + nested_offset = mul_s64_u64_shr((s64) l1_offset, l2_multiplier,
> + kvm_tsc_scaling_ratio_frac_bits);
> +
> + nested_offset += l2_offset;
> + return nested_offset;
> +}
> +EXPORT_SYMBOL_GPL(kvm_calc_nested_tsc_offset);
Looks OK.
> +
> +u64 kvm_calc_nested_tsc_multiplier(u64 l1_multiplier, u64 l2_multiplier)
> +{
> + if (l2_multiplier != kvm_default_tsc_scaling_ratio)
> + return mul_u64_u64_shr(l1_multiplier, l2_multiplier,
> + kvm_tsc_scaling_ratio_frac_bits);
> +
> + return l1_multiplier;
> +}
> +EXPORT_SYMBOL_GPL(kvm_calc_nested_tsc_multiplier);
Looks OK as well.
> +
> static void kvm_vcpu_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
> {
> vcpu->arch.l1_tsc_offset = offset;
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Best regards,
Maxim Levitsky
next prev parent reply other threads:[~2021-05-24 17:51 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
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 [this message]
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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