linux-kernel - Re: [PATCH v5 5/13] virt: gunyah: Add hypercalls to identify Gunyah

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Message-ID: <2b6804ff-5386-06bd-7c01-4e1cd4ad23f3@kernel.org>
Date:   Tue, 11 Oct 2022 08:22:03 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Elliot Berman <quic_eberman@...cinc.com>,
        Bjorn Andersson <quic_bjorande@...cinc.com>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Arnd Bergmann <arnd@...db.de>
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>,
        Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>,
        Andy Gross <agross@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        linux-arm-kernel@...ts.infradead.org,
        Marc Zyngier <maz@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 5/13] virt: gunyah: Add hypercalls to identify Gunyah

On 11. 10. 22, 2:08, Elliot Berman wrote:
> Add hypercalls to identify when Linux is running a virtual machine under
> Gunyah.
> 
> There are two calls to help identify Gunyah:
> 
> 1. gh_hypercall_get_uid() returns a UID when running under a Gunyah
>     hypervisor.
> 2. gh_hypercall_hyp_identify() returns build information and a set of
>     feature flags that are supported by Gunyah.
...
> --- /dev/null
> +++ b/arch/arm64/gunyah/hypercall.c
> @@ -0,0 +1,71 @@
...
> +/**
> + * gh_hypercall_get_uid() - Returns a UID when running under a Gunyah hypervisor.
> + * @uid: An array of 4 u32's (u32 uid[4];)
> + *
> + * The UID will be either QC_HYP_UID or GUNYAH_UID defined in include/asm-generic/gunyah.h.
> + * QC_HYP_UID is returned on platforms using Qualcomm's version of Gunyah.
> + * GUNYAH_UID is returned on platforms using open source version of Gunyah.
> + * If the uid is not one of the above two UIDs, then it is assumed that the hypervisor or firmware
> + * is not Gunyah.
> + */
> +void gh_hypercall_get_uid(u32 *uid)

So why this isn't u32 uid[4], or u32 uid[static 4] to aid the compiler 
(and limit users)?

> +{
> +	struct arm_smccc_res res;
> +
> +	arm_smccc_1_1_hvc(GH_HYPERCALL_CALL_UID, &res);
> +
> +	uid[0] = res.a0;
> +	uid[1] = res.a1;
> +	uid[2] = res.a2;
> +	uid[3] = res.a3;
> +}
> +EXPORT_SYMBOL_GPL(gh_hypercall_get_uid);

...

> --- a/include/asm-generic/gunyah.h
> +++ b/include/asm-generic/gunyah.h
> @@ -71,4 +71,40 @@ static inline int gh_remap_error(int gh_error)
...
> +#define GH_API_INFO_API_VERSION(x)	(((x) >> 0) & 0x3fff)
> +#define GH_API_INFO_BIG_ENDIAN(x)	(((x) >> 14) & 1)
> +#define GH_API_INFO_IS_64BIT(x)		(((x) >> 15) & 1)
> +#define GH_API_INFO_VARIANT(x)		(((x) >> 56) & 0xff)

Use GET_FIELD()?

regards,
-- 
-- 
js
suse labs