linux-kernel - Re: [PATCH v2 2/3] soc: qcom: rmtfs: Support discarding guard pages

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Message-ID: <ba3e6235-3976-6a86-ec4c-62a8786a1707@linaro.org>
Date:   Wed, 31 May 2023 01:09:21 +0100
From:   Caleb Connolly <caleb.connolly@...aro.org>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] soc: qcom: rmtfs: Support discarding guard pages



On 31/05/2023 01:08, Caleb Connolly wrote:
> 
> 
> On 31/05/2023 00:36, Bjorn Andersson wrote:
>> In some configurations, the exact placement of the rmtfs shared memory
>> region isn't so strict. The DeviceTree author can then choose to use the
>> "size" property and rely on the OS for placement (in combination with
>> "alloc-ranges", if desired).
>>
>> But on some platforms the rmtfs memory region may not be allocated
>> adjacent to regions allocated by other clients. Add support for
>> discarding the first and last 4k block in the region, if
>> qcom,use-guard-pages is specified in DeviceTree.
> 
> Oh nice!
... Bit eager on the enter key there
>>
>> Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>

Reviewed-by: Caleb Connolly <caleb.connolly@...aro.org>
>> ---
>>
>> Changes since v1:
>> - Drop the dma_alloc_coherent() based approach and just add support for
>>   the guard pages.
>>
>>  drivers/soc/qcom/rmtfs_mem.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/soc/qcom/rmtfs_mem.c b/drivers/soc/qcom/rmtfs_mem.c
>> index f83811f51175..28238974d913 100644
>> --- a/drivers/soc/qcom/rmtfs_mem.c
>> +++ b/drivers/soc/qcom/rmtfs_mem.c
>> @@ -213,6 +213,16 @@ static int qcom_rmtfs_mem_probe(struct platform_device *pdev)
>>  		goto put_device;
>>  	}
>>  
>> +	/*
>> +	 * If requested, discard the first and last 4k block in order to ensure
>> +	 * that the rmtfs region isn't adjacent to other protected regions.
>> +	 */
>> +	if (of_property_present(node, "qcom,use-guard-pages")) {
>> +		rmtfs_mem->addr += SZ_4K;
>> +		rmtfs_mem->base += SZ_4K;
>> +		rmtfs_mem->size -= 2 * SZ_4K;
>> +	}
>> +
>>  	cdev_init(&rmtfs_mem->cdev, &qcom_rmtfs_mem_fops);
>>  	rmtfs_mem->cdev.owner = THIS_MODULE;
>>  
> 

-- 
// Caleb (they/them)