linux-kernel - Re: [PATCH v3 0/8] KVM: x86: Add AMD Guest PerfMonV2 PMU support

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Message-ID: <Y8nqv9K/WUqhaBub@google.com>
Date:   Fri, 20 Jan 2023 01:13:35 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Like Xu <like.xu.linux@...il.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/8] KVM: x86: Add AMD Guest PerfMonV2 PMU support

On Fri, Nov 11, 2022, Like Xu wrote:
> Starting with Zen4, core PMU on AMD platforms such as Genoa and
> Ryzen-7000 will support PerfMonV2, and it is also compatible with
> legacy PERFCTR_CORE behavior and msr addresses.
> 
> If you don't have access to the hardware specification, the commits
> d6d0c7f681fd..7685665c390d for host perf can also bring a quick
> overview. Its main change is the addition of three msr's equivalent
> to Intel V2, namely global_ctrl, global_status, global_status_clear.
> 
> It is worth noting that this feature is very attractive for reducing the
> overhead of PMU virtualization, since multiple msr accesses to multiple
> counters will be replaced by a single access to the global register,
> plus more accuracy gain when multiple guest counters are used.

Some minor nits, though I haven't looked at the meat of the series yet.  I'll
give this a thorough review early next week (unless I'm extra ambitious tomorrow).