linux-kernel - Re: [PATCH v5 05/19] arm64: Add support for trace synchronization barrier

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Message-ID: <871rc4jzn0.wl-maz@kernel.org>
Date:   Wed, 24 Mar 2021 16:16:19 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        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,
        Will Deacon <will.deacon@....com>
Subject: Re: [PATCH v5 05/19] arm64: Add support for trace synchronization barrier

On Wed, 24 Mar 2021 15:51:14 +0000,
Suzuki K Poulose <suzuki.poulose@....com> wrote:
> 
> On 24/03/2021 13:49, Marc Zyngier wrote:
> > On Wed, 24 Mar 2021 09:39:13 +0000,
> > Suzuki K Poulose <suzuki.poulose@....com> wrote:
> >> 
> >> On 23/03/2021 18:21, Catalin Marinas wrote:
> >>> Hi Suzuki?
> >>> 
> >>> On Tue, Mar 23, 2021 at 12:06:33PM +0000, Suzuki K Poulose wrote:
> >>>> tsb csync synchronizes the trace operation of instructions.
> >>>> The instruction is a nop when FEAT_TRF is not implemented.
> >>>> 
> >>>> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> >>>> Cc: Mike Leach <mike.leach@...aro.org>
> >>>> Cc: Catalin Marinas <catalin.marinas@....com>
> >>>> Cc: Will Deacon <will.deacon@....com>
> >>>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> >>> 
> >>> How do you plan to merge these patches? If they go via the coresight
> >>> tree:
> >>> 
> >> 
> >> Ideally all of this should go via the CoreSight tree to have the
> >> dependencies solved at one place. But there are some issues :
> >> 
> >> If this makes to 5.13 queue for CoreSight,
> >> 
> >> 1) CoreSight next is based on rc2 at the moment and we have fixes gone
> >> into rc3 and later, which this series will depend on. (We could move
> >> the next tree forward to a later rc to solve this).
> >> 
> >> 2) There could be conflicts with the kvmarm tree for the KVM host
> >> changes (That has dependency on the TRBE definitions patch).
> >> 
> >> If it doesn't make to 5.13 queue, it would be good to have this patch,
> >> the TRBE defintions and the KVM host patches queued for 5.13 (not sure
> >> if this is acceptable) and we could rebase the CoreSight changes on 5.13
> >> and push it to next release.
> >> 
> >> I am open for other suggestions.
> >> 
> >> Marc, Mathieu,
> >> 
> >> Thoughts ?
> > 
> > I was planning to take the first two patches in 5.12 as fixes (they
> > are queued already, and would hopefully land in -rc5). If that doesn't
> > fit with the plan, please let me know ASAP.
> 
> Marc,
> 
> I think it would be better to hold on pushing those patches until we
> have a clarity on how things will go.

OK. I thought there was a need for these patches to prevent guest
access to the v8.4 self hosted tracing feature that went in 5.12
though[1]... Did I get it wrong?

Thanks,

	M.

[1] https://lore.kernel.org/r/cbe4ef17-38f9-c555-d838-796be752d4a3@arm.com

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