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

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Date:   Mon, 22 Nov 2021 11:56:16 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Michael Kelley <mikelley@...rosoft.com>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Steven Price <steven.price@....com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] firmware: smccc: Fix check for ARCH_SOC_ID not implemented

On Mon, Nov 22, 2021 at 9:35 AM Sudeep Holla <sudeep.holla@....com> wrote:
> 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.

In general, I think the easiest way would be for you to forward the
patch with your Signed-off-by, when you don't have other material
for a pull request.

I've applied this patch from the list now.

       Arnd