linux-kernel - Re: [PATCH 1/1] firmware: smccc: Fix check for ARCH_SOC

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Date:   Mon, 22 Nov 2021 08:35:03 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Michael Kelley <mikelley@...rosoft.com>
Cc:     mark.rutland@....com, lorenzo.pieralisi@....com,
        steven.price@....com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH 1/1] firmware: smccc: Fix check for ARCH_SOC_ID not
 implemented

On Fri, Nov 19, 2021 at 03:39:01PM -0800, Michael Kelley wrote:
> The ARCH_FEATURES function ID is a 32-bit SMC call, which returns
> a 32-bit result per the SMCCC spec.  Current code is doing a 64-bit
> comparison against -1 (SMCCC_RET_NOT_SUPPORTED) to detect that the
> feature is unimplemented.  That check doesn't work in a Hyper-V VM,
> where the upper 32-bits are zero as allowed by the spec.
> 
> Cast the result as an 'int' so the comparison works. The change also
> makes the code consistent with other similar checks in this file.
> 
> Fixes: 821b67fa4639 ("firmware: smccc: Add ARCH_SOC_ID support")

Good catch.

Reviewed-by: Sudeep Holla <sudeep.holla@....com>

Can you please re-post with my review tag keeping arm@...nel.org and
soc@...nel.org ? I don't have any other fixes at the moment, we can
ask SoC maintainers to fix this up directly.

-- 
Regards,
Sudeep