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Date:   Wed, 30 Nov 2022 11:41:56 +0200
From:   Mike Rapoport <rppt@kernel.org>
To:     Song Liu <song@kernel.org>
Cc:     Luis Chamberlain <mcgrof@kernel.org>, bpf@vger.kernel.org,
        linux-mm@kvack.org, akpm@linux-foundation.org, x86@kernel.org,
        peterz@infradead.org, hch@lst.de, rick.p.edgecombe@intel.com,
        willy@infradead.org, dave@stgolabs.net, a.manzanares@samsung.com
Subject: Re: [PATCH bpf-next v4 0/6] execmem_alloc for BPF programs
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On Mon, Nov 21, 2022 at 07:28:36PM -0700, Song Liu wrote:
> On Mon, Nov 21, 2022 at 1:12 PM Luis Chamberlain <mcgrof@kernel.org> wrote:
> >
> > Also, you mention your perf stats are run on a VM, I am curious what
> > things you need to get TLB to be properly measured on the VM and if
> > this is really reliable data Vs bare metal. I haven't yet been sucessful
> > on getting perf stat for TBL to work on a VM and based on what I've read
> > have been catious about the results.
> 
> To make these perf counters work on VM, we need a newer host kernel
> (my system is running 5.6 based kernel, but I am not sure what is the
> minimum required version). Then we need to run qemu with option
> "-cpu host" (both host and guest are x86_64).
> 
> >
> > So curious if you'd see something different on bare metal.
> 
> Once the above all worked out, VM runs the same as bare metal from
> perf counter's point of view.

TLBs behave differently because of EPT.

-- 
Sincerely yours,
Mike.