linux-kernel - Re: [PATCH v10 15/26] gunyah: rsc_mgr: Add platform ops on mem_lend/mem

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Date:   Tue, 21 Feb 2023 13:22:51 -0800
From:   Elliot Berman <quic_eberman@...cinc.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Alex Elder <elder@...aro.org>,
        Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>
CC:     Murali Nalajala <quic_mnalajal@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
        Carl van Schaik <quic_cvanscha@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        "Konrad Dybcio" <konrad.dybcio@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Bagas Sanjaya <bagasdotme@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Jassi Brar <jassisinghbrar@...il.com>,
        <linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v10 15/26] gunyah: rsc_mgr: Add platform ops on
 mem_lend/mem_reclaim



On 2/21/2023 6:51 AM, Srinivas Kandagatla wrote:
> 
> 
> On 14/02/2023 21:24, Elliot Berman wrote:
[snip]
>> +
>> +static struct gunyah_rm_platform_ops *rm_platform_ops;
>> +static DECLARE_RWSEM(rm_platform_ops_lock);
> 
> Why do we need this read/write lock or this global rm_platform_ops here, 
> AFAIU, there will be only one instance of platform_ops per platform.
> 
> This should be a core part of the gunyah and its driver early setup, 
> that should give us pretty much lock less behaviour.
> 
> We should be able to determine by Hypervisor UUID that its on Qualcomm 
> platform or not, during early gunyah setup which should help us setup 
> the platfrom ops accordingly.
> 
> This should also help cleanup some of the gunyah code that was added 
> futher down in this patchset.

I'm guessing the direction to take is:

   config GUNYAH
     select QCOM_SCM if ARCH_QCOM

and have vm_mgr call directly into qcom_scm driver if the UID matches?

We have an Android requirement to enable CONFIG_GUNYAH=y and 
CONFIG_QCOM_SCM=m, but it wouldn't be possible with this design. The 
platform hooks implementation allows GUNYAH and QCOM_SCM to be enabled 
without setting lower bound of the other.

- Elliot