linux-kernel - Re: [PATCH v3 2/6] arm64: KVM: Move SPE and trace registers to the sysreg array

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Message-ID: <1aca6009-9943-d0ee-0fa9-b88b33fd0540@arm.com>
Date:   Mon, 4 Dec 2023 16:17:43 +0000
From:   James Clark <james.clark@....com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.linux.dev, suzuki.poulose@....com, broonie@...nel.org,
        Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Rob Herring <robh@...nel.org>,
        Jintack Lim <jintack.lim@...aro.org>,
        Akihiko Odaki <akihiko.odaki@...nix.com>,
        Fuad Tabba <tabba@...gle.com>, Joey Gouly <joey.gouly@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/6] arm64: KVM: Move SPE and trace registers to the
 sysreg array



On 04/12/2023 09:29, Marc Zyngier wrote:
> On Thu, 19 Oct 2023 17:55:00 +0100,
> James Clark <james.clark@....com> wrote:
>>
>> pmscr_el1 and trfcr_el1 are currently special cased in the
>> host_debug_state struct, but they're just registers after all so give
>> them entries in the sysreg array and refer to them through the host
>> context.
>>
>> Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
>> Signed-off-by: James Clark <james.clark@....com>
>> ---
>>  arch/arm64/include/asm/kvm_host.h  |  6 ++--
>>  arch/arm64/include/asm/kvm_hyp.h   |  4 +--
>>  arch/arm64/kvm/hyp/nvhe/debug-sr.c | 44 +++++++++++++++---------------
>>  arch/arm64/kvm/hyp/nvhe/switch.c   |  4 +--
>>  4 files changed, 28 insertions(+), 30 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 4a966c0d7373..7c82927ddaf2 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -437,6 +437,8 @@ enum vcpu_sysreg {
>>  	CNTHP_CVAL_EL2,
>>  	CNTHV_CTL_EL2,
>>  	CNTHV_CVAL_EL2,
>> +	PMSCR_EL1,	/* Statistical profiling extension */
>> +	TRFCR_EL1,	/* Self-hosted trace filters */
> 
> Why this move? Are you also adding guest support for SPE?
> 
> Until you do, I don't see the need to pollute the guest's sysreg
> namespace.
> 
> 	M.
> 

Ah ok yes, I think I misunderstood your previous review comment. You're
right I don't touch SPE and it's only ever for the host so I can leave
it where it was in struct host_debug_state.

James