linux-kernel - Re: [PATCH v5 07/19] arm64: kvm: Enable access to TRBE support for host

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Date:   Tue, 30 Mar 2021 11:16:42 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:     Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        coresight@...ts.linaro.org, mike.leach@...aro.org,
        leo.yan@...aro.org, anshuman.khandual@....com,
        catalin.marinas@....com, Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v5 07/19] arm64: kvm: Enable access to TRBE support for host

Hi Mathieu,

On Fri, 26 Mar 2021 16:55:50 +0000,
Mathieu Poirier <mathieu.poirier@...aro.org> wrote:
> 
> On Tue, Mar 23, 2021 at 12:06:35PM +0000, Suzuki K Poulose wrote:
> > For a nvhe host, the EL2 must allow the EL1&0 translation
> > regime for TraceBuffer (MDCR_EL2.E2TB == 0b11). This must
> > be saved/restored over a trip to the guest. Also, before
> > entering the guest, we must flush any trace data if the
> > TRBE was enabled. And we must prohibit the generation
> > of trace while we are in EL1 by clearing the TRFCR_EL1.
> > 
> > For vhe, the EL2 must prevent the EL1 access to the Trace
> > Buffer.
> > 
> > Cc: Will Deacon <will@...nel.org>
> > Cc: Catalin Marinas <catalin.marinas@....com>
> > Cc: Marc Zyngier <maz@...nel.org>
> > Cc: Mark Rutland <mark.rutland@....com>
> > Cc: Anshuman Khandual <anshuman.khandual@....com>
> > Acked-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> > ---
> >  arch/arm64/include/asm/el2_setup.h | 13 +++++++++
> >  arch/arm64/include/asm/kvm_arm.h   |  2 ++
> >  arch/arm64/include/asm/kvm_host.h  |  2 ++
> >  arch/arm64/kernel/hyp-stub.S       |  3 ++-
> >  arch/arm64/kvm/debug.c             |  6 ++---
> >  arch/arm64/kvm/hyp/nvhe/debug-sr.c | 42 ++++++++++++++++++++++++++++++
> >  arch/arm64/kvm/hyp/nvhe/switch.c   |  1 +
> >  7 files changed, 65 insertions(+), 4 deletions(-)
> > 
> 
> Marc - do you want me to pick up this one?

I just went through the KVM patch, and I have a couple of question
that Suzuki can hopefully address quickly enough. As for merging it
via your tree, I'm worried that it will conflict with other patches
that are in flight.

We can hopefully set up a stable branch between the two trees.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.