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From: Jim Mattson <jmattson@google.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: kvm list <kvm@vger.kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Like Xu <like.xu@linux.intel.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] KVM: SVM: drop MSR_IA32_PERF_CAPABILITIES from emulated MSRs
Date: Wed, 17 Jun 2020 09:47:01 -0700	[thread overview]
Message-ID: <CALMp9eQCbKz5aeacvMvBX4kq5Oxy5Tap3dUT4SZ_dnO-zmrPVQ@mail.gmail.com> (raw)
In-Reply-To: <87wo45hqhy.fsf@vitty.brq.redhat.com>

On Wed, Jun 17, 2020 at 4:38 AM Vitaly Kuznetsov <vkuznets@redhat.com> wrote:

> Side note: MSR_IA32_PERF_CAPABILITIES can be returned by both
> KVM_GET_MSR_INDEX_LIST and KVM_GET_MSR_FEATURE_INDEX_LIST as we have it
> both as an emulated MSR filtered by kvm_x86_ops.has_emulated_msr() and
> a feature msr filtered by kvm_x86_ops.get_msr_feature(). But the later
> is a whitelist so MSR_IA32_PERF_CAPABILITIES won't appear on AMD and the
> promise "can be passed to the KVM_GET_MSRS" is kept.

So, how is MSR_IA32_PERF_CAPABILITIES different from, say,
MSR_K7_HWCR, which by its very name doesn't sound like it would be
supported on Intel CPUs? Why not just emulate
MSR_IA32_PERF_CAPABILITIES on AMD, just as we emulate MSR_K7_HWCR on
Intel?

My concern is that we don't seem to have a standard here. Each
individual MSR is handled ad hoc, which adds unnecessary complexity.

  reply	other threads:[~2020-06-17 16:47 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-16 16:14 [PATCH] KVM: SVM: drop MSR_IA32_PERF_CAPABILITIES from emulated MSRs Vitaly Kuznetsov
2020-06-16 16:24 ` Jim Mattson
2020-06-16 16:45   ` Vitaly Kuznetsov
2020-06-16 16:52     ` Jim Mattson
2020-06-17 11:38       ` Vitaly Kuznetsov
2020-06-17 16:47         ` Jim Mattson [this message]
2020-06-17 17:17         ` Paolo Bonzini
2020-06-18 11:08           ` Vitaly Kuznetsov

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