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Date:   Mon, 9 Jan 2023 15:34:29 -0600
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From:   Alex Elder <elder@linaro.org>
Subject: Re: [PATCH v8 06/28] virt: gunyah: Identify hypervisor version
To:     Elliot Berman <quic_eberman@quicinc.com>,
        Bjorn Andersson <quic_bjorande@quicinc.com>,
        Murali Nalajala <quic_mnalajal@quicinc.com>
Cc:     Trilok Soni <quic_tsoni@quicinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@quicinc.com>,
        Carl van Schaik <quic_cvanscha@quicinc.com>,
        Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Bagas Sanjaya <bagasdotme@gmail.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Jassi Brar <jassisinghbrar@gmail.com>,
        Sudeep Holla <sudeep.holla@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Lorenzo Pieralisi <lpieralisi@kernel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
        linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-acpi@vger.kernel.org
References: <20221219225850.2397345-1-quic_eberman@quicinc.com>
 <20221219225850.2397345-7-quic_eberman@quicinc.com>
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On 12/19/22 4:58 PM, Elliot Berman wrote:
> Export the version of Gunyah which is reported via the hyp_identify
> hypercall. Increments of the major API version indicate possibly
> backwards incompatible changes.
> 
> Export the hypervisor identity so that Gunyah drivers can act according
> to the major API version.
> 
> Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
> ---
>   drivers/virt/Makefile        |  1 +
>   drivers/virt/gunyah/Makefile |  1 +
>   drivers/virt/gunyah/gunyah.c | 46 ++++++++++++++++++++++++++++++++++++
>   include/linux/gunyah.h       |  6 +++++
>   4 files changed, 54 insertions(+)
>   create mode 100644 drivers/virt/gunyah/Makefile
>   create mode 100644 drivers/virt/gunyah/gunyah.c
> 
> diff --git a/drivers/virt/Makefile b/drivers/virt/Makefile
> index 093674e05c40..92b7e5311548 100644
> --- a/drivers/virt/Makefile
> +++ b/drivers/virt/Makefile
> @@ -11,3 +11,4 @@ obj-$(CONFIG_NITRO_ENCLAVES)	+= nitro_enclaves/
>   obj-$(CONFIG_ACRN_HSM)		+= acrn/
>   obj-$(CONFIG_EFI_SECRET)	+= coco/efi_secret/
>   obj-$(CONFIG_SEV_GUEST)		+= coco/sev-guest/
> +obj-y				+= gunyah/
> diff --git a/drivers/virt/gunyah/Makefile b/drivers/virt/gunyah/Makefile
> new file mode 100644
> index 000000000000..2ac4ee64b89d
> --- /dev/null
> +++ b/drivers/virt/gunyah/Makefile
> @@ -0,0 +1 @@
> +obj-$(CONFIG_GUNYAH) += gunyah.o
> diff --git a/drivers/virt/gunyah/gunyah.c b/drivers/virt/gunyah/gunyah.c
> new file mode 100644
> index 000000000000..c34c9046fc08
> --- /dev/null
> +++ b/drivers/virt/gunyah/gunyah.c
> @@ -0,0 +1,46 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#define pr_fmt(fmt) "gunyah: " fmt
> +
> +#include <linux/gunyah.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/printk.h>
> +
> +struct gh_hypercall_hyp_identify_resp gunyah_api;
> +EXPORT_SYMBOL_GPL(gunyah_api);
> +
> +static const uint32_t gunyah_known_uuids[][4] = {
> +	{0x19bd54bd, 0x0b37571b, 0x946f609b, 0x54539de6}, /* QC_HYP (Qualcomm's build) */
> +	{0x673d5f14, 0x9265ce36, 0xa4535fdb, 0xc1d58fcd}, /* GUNYAH (open source build) */
> +};
> +
> +static int __init gunyah_init(void)
> +{
> +	u32 uid[4];
> +	int i;
> +
> +	gh_hypercall_get_uid(uid);
> +
> +	for (i = 0; i < ARRAY_SIZE(gunyah_known_uuids); i++)
> +		if (!memcmp(uid, gunyah_known_uuids[i], sizeof(uid)))
> +			break;
> +
> +	if (i == ARRAY_SIZE(gunyah_known_uuids))
> +		return -ENODEV;
> +
> +	gh_hypercall_hyp_identify(&gunyah_api);
> +
> +	pr_info("Running under Gunyah hypervisor %llx/v%u\n",
> +		FIELD_GET(GH_API_INFO_VARIANT_MASK, gunyah_api.api_info),
> +		gh_api_version());
> +
> +	return 0;
> +}
> +arch_initcall(gunyah_init);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Gunyah Hypervisor Driver");
> diff --git a/include/linux/gunyah.h b/include/linux/gunyah.h
> index 2765d2b40198..166156f69df9 100644
> --- a/include/linux/gunyah.h
> +++ b/include/linux/gunyah.h
> @@ -92,6 +92,12 @@ struct gh_hypercall_hyp_identify_resp {
>   	u64 api_info;
>   	u64 flags[3];
>   };
> +extern struct gh_hypercall_hyp_identify_resp gunyah_api;

Must this global variable be exposed?  Can't you hide it--as
well as its interpretation--inside "gunyah.c"?

> +
> +static inline u16 gh_api_version(void)
> +{
> +	return FIELD_GET(GH_API_INFO_API_VERSION_MASK, gunyah_api.api_info);
> +}

If you don't make the above function inline, can you hide the
definition of gunyah_api?

					-Alex

>   void gh_hypercall_get_uid(u32 uid[4]);
>   void gh_hypercall_hyp_identify(struct gh_hypercall_hyp_identify_resp *hyp_identity);