Re: [PATCH v3 4/7] arm64: hyperv: Boot in a Virtual Trust Level

[Wei Liu <wei.liu@kernel.org>]

On Fri, Jul 26, 2024 at 03:59:07PM -0700, Roman Kisel wrote:
> To run in the VTL mode, Hyper-V drivers have to know what
> VTL the system boots in, and the arm64/hyperv code does not
> update the variable that stores the value.
> 
> Update the variable to enable the Hyper-V drivers to boot
> in the VTL mode and print the VTL the code runs in.
> 
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
> ---
>  arch/arm64/hyperv/Makefile        |  1 +
>  arch/arm64/hyperv/hv_vtl.c        | 13 +++++++++++++
>  arch/arm64/hyperv/mshyperv.c      |  4 ++++
>  arch/arm64/include/asm/mshyperv.h |  7 +++++++
>  4 files changed, 25 insertions(+)
>  create mode 100644 arch/arm64/hyperv/hv_vtl.c
> 
> diff --git a/arch/arm64/hyperv/Makefile b/arch/arm64/hyperv/Makefile
> index 87c31c001da9..9701a837a6e1 100644
> --- a/arch/arm64/hyperv/Makefile
> +++ b/arch/arm64/hyperv/Makefile
> @@ -1,2 +1,3 @@
>  # SPDX-License-Identifier: GPL-2.0
>  obj-y		:= hv_core.o mshyperv.o
> +obj-$(CONFIG_HYPERV_VTL_MODE)	+= hv_vtl.o
> diff --git a/arch/arm64/hyperv/hv_vtl.c b/arch/arm64/hyperv/hv_vtl.c
> new file mode 100644
> index 000000000000..38642b7b6be0
> --- /dev/null
> +++ b/arch/arm64/hyperv/hv_vtl.c
> @@ -0,0 +1,13 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2024, Microsoft, Inc.
> + *
> + * Author : Roman Kisel <romank@linux.microsoft.com>
> + */
> +
> +#include <asm/mshyperv.h>
> +
> +void __init hv_vtl_init_platform(void)
> +{
> +	pr_info("Linux runs in Hyper-V Virtual Trust Level\n");
> +}
> diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c
> index 341f98312667..8fd04d6e4800 100644
> --- a/arch/arm64/hyperv/mshyperv.c
> +++ b/arch/arm64/hyperv/mshyperv.c
> @@ -98,6 +98,10 @@ static int __init hyperv_init(void)
>  		return ret;
>  	}
>  
> +	/* Find the VTL */
> +	ms_hyperv.vtl = get_vtl();
> +	hv_vtl_init_platform();

It doesn't make sense to me because this function unconditionally prints
Linux runs in Hyper-V Virtual Trust Level.

Thanks,
Wei.

> +
>  	ms_hyperv_late_init();
>  
>  	hyperv_initialized = true;
> diff --git a/arch/arm64/include/asm/mshyperv.h b/arch/arm64/include/asm/mshyperv.h
> index a7a3586f7cb1..63d6bb6998fc 100644
> --- a/arch/arm64/include/asm/mshyperv.h
> +++ b/arch/arm64/include/asm/mshyperv.h
> @@ -49,6 +49,13 @@ static inline u64 hv_get_msr(unsigned int reg)
>  				ARM_SMCCC_OWNER_VENDOR_HYP,	\
>  				HV_SMCCC_FUNC_NUMBER)
>  
> +#ifdef CONFIG_HYPERV_VTL_MODE
> +void __init hv_vtl_init_platform(void);
> +int __init hv_vtl_early_init(void);
> +#else
> +static inline void __init hv_vtl_init_platform(void) {}
> +#endif
> +
>  #include <asm-generic/mshyperv.h>
>  
>  #define ARM_SMCCC_VENDOR_HYP_UID_HYPERV_REG_0	0x7948734d
> -- 
> 2.34.1
>