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 01/12] math64.h: Add mul_s64_u64_shr()
Date: Mon, 24 May 2021 20:49:13 +0300 [thread overview]
Message-ID: <f6913c3669e156372c3d8e94946f2ec0dfc97020.camel@redhat.com> (raw)
In-Reply-To: <20210521102449.21505-2-ilstam@amazon.com>
On Fri, 2021-05-21 at 11:24 +0100, Ilias Stamatis wrote:
> This function is needed for KVM's nested virtualization. The nested TSC
> scaling implementation requires multiplying the signed TSC offset with
> the unsigned TSC multiplier.
>
> Signed-off-by: Ilias Stamatis <ilstam@amazon.com>
> ---
> include/linux/math64.h | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/include/linux/math64.h b/include/linux/math64.h
> index 66deb1fdc2ef..2928f03d6d46 100644
> --- a/include/linux/math64.h
> +++ b/include/linux/math64.h
> @@ -3,6 +3,7 @@
> #define _LINUX_MATH64_H
>
> #include <linux/types.h>
> +#include <linux/math.h>
> #include <vdso/math64.h>
> #include <asm/div64.h>
>
> @@ -234,6 +235,24 @@ static inline u64 mul_u64_u64_shr(u64 a, u64 b, unsigned int shift)
>
> #endif
>
> +#ifndef mul_s64_u64_shr
> +static inline u64 mul_s64_u64_shr(s64 a, u64 b, unsigned int shift)
> +{
> + u64 ret;
> +
> + /*
> + * Extract the sign before the multiplication and put it back
> + * afterwards if needed.
> + */
> + ret = mul_u64_u64_shr(abs(a), b, shift);
> +
> + if (a < 0)
> + ret = -((s64) ret);
> +
> + return ret;
> +}
> +#endif /* mul_s64_u64_shr */
> +
> #ifndef mul_u64_u32_div
> static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 divisor)
> {
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Best regards,
Maxim Levitsky
next prev parent reply other threads:[~2021-05-24 17:49 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 [this message]
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
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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