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Date:   Fri, 31 Mar 2023 09:24:55 -0500
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From:   Alex Elder <elder@linaro.org>
Subject: Re: [PATCH v11 05/26] virt: gunyah: Identify hypervisor version
To:     Elliot Berman <quic_eberman@quicinc.com>,
        Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
Cc:     Murali Nalajala <quic_mnalajal@quicinc.com>,
        Trilok Soni <quic_tsoni@quicinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@quicinc.com>,
        Carl van Schaik <quic_cvanscha@quicinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        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>,
        Will Deacon <will@kernel.org>, Andy Gross <agross@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Jassi Brar <jassisinghbrar@gmail.com>,
        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
References: <20230304010632.2127470-1-quic_eberman@quicinc.com>
 <20230304010632.2127470-6-quic_eberman@quicinc.com>
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On 3/3/23 7:06 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>

Looks good.

Reviewed-by: Alex Elder <elder@linaro.org>

> ---
>   drivers/virt/Makefile        |  1 +
>   drivers/virt/gunyah/Makefile |  3 ++
>   drivers/virt/gunyah/gunyah.c | 57 ++++++++++++++++++++++++++++++++++++
>   3 files changed, 61 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 e9aa6fc96fab..a5817e2d7d71 100644
> --- a/drivers/virt/Makefile
> +++ b/drivers/virt/Makefile
> @@ -12,3 +12,4 @@ obj-$(CONFIG_ACRN_HSM)		+= acrn/
>   obj-$(CONFIG_EFI_SECRET)	+= coco/efi_secret/
>   obj-$(CONFIG_SEV_GUEST)		+= coco/sev-guest/
>   obj-$(CONFIG_INTEL_TDX_GUEST)	+= coco/tdx-guest/
> +obj-y				+= gunyah/
> diff --git a/drivers/virt/gunyah/Makefile b/drivers/virt/gunyah/Makefile
> new file mode 100644
> index 000000000000..34f32110faf9
> --- /dev/null
> +++ b/drivers/virt/gunyah/Makefile
> @@ -0,0 +1,3 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +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..4b7e6f3edaff
> --- /dev/null
> +++ b/drivers/virt/gunyah/gunyah.c
> @@ -0,0 +1,57 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2022-2023 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>
> +
> +static struct gh_hypercall_hyp_identify_resp gh_api;
> +
> +u16 gh_api_version(void)
> +{
> +	return FIELD_GET(GH_API_INFO_API_VERSION_MASK, gh_api.api_info);
> +}
> +EXPORT_SYMBOL_GPL(gh_api_version);
> +
> +bool gh_api_has_feature(enum gh_api_feature feature)
> +{
> +	switch (feature) {
> +	case GH_FEATURE_DOORBELL:
> +	case GH_FEATURE_MSGQUEUE:
> +	case GH_FEATURE_VCPU:
> +	case GH_FEATURE_MEMEXTENT:
> +		return !!(gh_api.flags[0] & BIT_ULL(feature));
> +	default:
> +		return false;
> +	}
> +}
> +EXPORT_SYMBOL_GPL(gh_api_has_feature);
> +
> +static int __init gh_init(void)
> +{
> +	if (!arch_is_gh_guest())
> +		return -ENODEV;
> +
> +	gh_hypercall_hyp_identify(&gh_api);
> +
> +	pr_info("Running under Gunyah hypervisor %llx/v%u\n",
> +		FIELD_GET(GH_API_INFO_VARIANT_MASK, gh_api.api_info),
> +		gh_api_version());
> +
> +	/* We might move this out to individual drivers if there's ever an API version bump */
> +	if (gh_api_version() != GH_API_V1) {
> +		pr_info("Unsupported Gunyah version: %u\n", gh_api_version());
> +		return -ENODEV;
> +	}
> +
> +	return 0;
> +}
> +arch_initcall(gh_init);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Gunyah Hypervisor Driver");