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From: "Stamatis, Ilias" <ilstam@amazon.com>
To: "jmattson@google.com" <jmattson@google.com>,
	"ilstam@mailbox.org" <ilstam@mailbox.org>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"Woodhouse, David" <dwmw@amazon.co.uk>,
	"vkuznets@redhat.com" <vkuznets@redhat.com>,
	"mtosatti@redhat.com" <mtosatti@redhat.com>,
	"joro@8bytes.org" <joro@8bytes.org>,
	"zamsden@gmail.com" <zamsden@gmail.com>,
	"seanjc@google.com" <seanjc@google.com>,
	"pbonzini@redhat.com" <pbonzini@redhat.com>,
	"wanpengli@tencent.com" <wanpengli@tencent.com>
Subject: Re: [PATCH 0/8] KVM: VMX: Implement nested TSC scaling
Date: Thu, 6 May 2021 17:48:26 +0000	[thread overview]
Message-ID: <fccb8b01aadfb7e53f8711100bc10dc1c98c5cd5.camel@amazon.com> (raw)
In-Reply-To: <CALMp9eSNHf=vmqeer+ZkRa3NhJoLMbEO+OZJaG9qf+2+TQ2grA@mail.gmail.com>

On Thu, 2021-05-06 at 10:16 -0700, Jim Mattson wrote:
> On Thu, May 6, 2021 at 3:34 AM <ilstam@mailbox.org> wrote:
> > 
> > From: Ilias Stamatis <ilstam@amazon.com>
> > 
> > KVM currently supports hardware-assisted TSC scaling but only for L1
> > and it
> > doesn't expose the feature to nested guests. This patch series adds
> > support for
> > nested TSC scaling and allows both L1 and L2 to be scaled with
> > different
> > scaling factors.
> > 
> > When scaling and offsetting is applied, the TSC for the guest is
> > calculated as:
> > 
> > (TSC * multiplier >> 48) + offset
> > 
> > With nested scaling the values in VMCS01 and VMCS12 need to be
> > merged
> > together and stored in VMCS02.
> > 
> > The VMCS02 values are calculated as follows:
> > 
> > offset_02 = ((offset_01 * mult_12) >> 48) + offset_12
> > mult_02 = (mult_01 * mult_12) >> 48
> > 
> > The last patch of the series adds a KVM selftest.
> 
> Will you be doing the same for SVM? The last time I tried to add a
> nested virtualization feature for Intel only, Paolo rapped my knuckles
> with a ruler.

Yes, I can try do this, if it's not much more complicated, once I get
access to AMD hardware. 

But I suppose this series is standalone and could be merged separately?
By taking a quick look it seems that SVM exposes far less features to
nested guests than VMX does anyway.

Ilias

  reply	other threads:[~2021-05-06 17:48 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-06 10:32 ilstam
2021-05-06 10:32 ` [PATCH 1/8] KVM: VMX: Add a TSC multiplier field in VMCS12 ilstam
2021-05-06 14:50   ` kernel test robot
2021-05-06 17:36   ` Jim Mattson
2021-05-10 13:42   ` Maxim Levitsky
2021-05-06 10:32 ` [PATCH 2/8] KVM: X86: Store L1's TSC scaling ratio in 'struct kvm_vcpu_arch' ilstam
2021-05-10 13:43   ` Maxim Levitsky
2021-05-06 10:32 ` [PATCH 3/8] KVM: X86: Pass an additional 'L1' argument to kvm_scale_tsc() ilstam
2021-05-10 13:52   ` Maxim Levitsky
2021-05-10 15:44     ` Stamatis, Ilias
2021-05-06 10:32 ` [PATCH 4/8] KVM: VMX: Adjust the TSC-related VMCS fields on L2 entry and exit ilstam
2021-05-06 11:32   ` Paolo Bonzini
2021-05-06 17:35     ` Stamatis, Ilias
2021-05-10 14:11       ` Paolo Bonzini
2021-05-10 13:53   ` Maxim Levitsky
2021-05-10 14:44     ` Stamatis, Ilias
2021-05-11 12:38       ` Maxim Levitsky
2021-05-11 15:11         ` Stamatis, Ilias
2021-05-06 10:32 ` [PATCH 5/8] KVM: X86: Move tracing outside write_l1_tsc_offset() ilstam
2021-05-10 13:54   ` Maxim Levitsky
2021-05-06 10:32 ` [PATCH 6/8] KVM: VMX: Make vmx_write_l1_tsc_offset() work with nested TSC scaling ilstam
2021-05-10 13:54   ` Maxim Levitsky
2021-05-10 16:08     ` Stamatis, Ilias
2021-05-11 12:44       ` Maxim Levitsky
2021-05-11 17:44         ` Stamatis, Ilias
2021-05-06 10:32 ` [PATCH 7/8] KVM: VMX: Expose TSC scaling to L2 ilstam
2021-05-10 13:56   ` Maxim Levitsky
2021-05-06 10:32 ` [PATCH 8/8] KVM: selftests: x86: Add vmx_nested_tsc_scaling_test ilstam
2021-05-10 13:59   ` Maxim Levitsky
2021-05-11 11:16     ` Stamatis, Ilias
2021-05-11 12:47       ` Maxim Levitsky
2021-05-11 14:02         ` Stamatis, Ilias
2021-05-06 17:16 ` [PATCH 0/8] KVM: VMX: Implement nested TSC scaling Jim Mattson
2021-05-06 17:48   ` Stamatis, Ilias [this message]
2021-05-10 13:43     ` Maxim Levitsky
2021-05-10 14:29   ` Paolo Bonzini

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