linux-kernel - Re: [PATCH] KVM: selftests: Use data load to trigger LLC references/misses in Intel PMU

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Message-ID: <173645118101.885497.8247079551108053264.b4-ty@google.com>
Date: Thu,  9 Jan 2025 11:47:17 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Maxim Levitsky <mlevitsk@...hat.com>
Subject: Re: [PATCH] KVM: selftests: Use data load to trigger LLC
 references/misses in Intel PMU

On Wed, 27 Nov 2024 15:56:27 -0800, Sean Christopherson wrote:
> In the PMU counters test, add a data load in the measured loop and target
> the data with CLFLUSH{OPT} in order to (try to) guarantee the loop
> generates LLC misses and fills.  Per the SDM, some hardware prefetchers
> are allowed to omit relevant PMU events, and Emerald Rapids (and possibly
> Sapphire Rapids) appears to have gained an instruction prefetcher that
> bypasses event counts.  E.g. the test will consistently fail on EMR CPUs,
> but then pass with seemingly benign changes to the code.
> 
> [...]

Applied to kvm-x86 selftests, thanks!

[1/1] KVM: selftests: Use data load to trigger LLC references/misses in Intel PMU
      https://github.com/kvm-x86/linux/commit/7803339fa929

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https://github.com/kvm-x86/linux/tree/next