RE: [PATCH V3 02/13] x86/HV: Initialize shared memory boundary in the Isolation VM.

[Michael Kelley <mikelley@microsoft.com>]

From: Tianyu Lan <ltykernel@gmail.com> Sent: Monday, August 9, 2021 10:56 AM
> Subject: [PATCH V3 02/13] x86/HV: Initialize shared memory boundary in the Isolation VM.

As with Patch 1, use the "x86/hyperv:" tag in the Subject line.

> 
> From: Tianyu Lan <Tianyu.Lan@microsoft.com>
> 
> Hyper-V exposes shared memory boundary via cpuid
> HYPERV_CPUID_ISOLATION_CONFIG and store it in the
> shared_gpa_boundary of ms_hyperv struct. This prepares
> to share memory with host for SNP guest.
> 
> Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
> ---
>  arch/x86/kernel/cpu/mshyperv.c |  2 ++
>  include/asm-generic/mshyperv.h | 12 +++++++++++-
>  2 files changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 6b5835a087a3..2b7f396ef1a5 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -313,6 +313,8 @@ static void __init ms_hyperv_init_platform(void)
>  	if (ms_hyperv.priv_high & HV_ISOLATION) {
>  		ms_hyperv.isolation_config_a = cpuid_eax(HYPERV_CPUID_ISOLATION_CONFIG);
>  		ms_hyperv.isolation_config_b = cpuid_ebx(HYPERV_CPUID_ISOLATION_CONFIG);
> +		ms_hyperv.shared_gpa_boundary =
> +			(u64)1 << ms_hyperv.shared_gpa_boundary_bits;

You could use BIT_ULL() here, but it's kind of a shrug.

> 
>  		pr_info("Hyper-V: Isolation Config: Group A 0x%x, Group B 0x%x\n",
>  			ms_hyperv.isolation_config_a, ms_hyperv.isolation_config_b);
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index 4269f3174e58..aa26d24a5ca9 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -35,8 +35,18 @@ struct ms_hyperv_info {
>  	u32 max_vp_index;
>  	u32 max_lp_index;
>  	u32 isolation_config_a;
> -	u32 isolation_config_b;
> +	union {
> +		u32 isolation_config_b;
> +		struct {
> +			u32 cvm_type : 4;
> +			u32 Reserved11 : 1;
> +			u32 shared_gpa_boundary_active : 1;
> +			u32 shared_gpa_boundary_bits : 6;
> +			u32 Reserved12 : 20;

Any reason to name the reserved fields as "11" and "12"?  It
just looks a bit unusual.  And I'd suggest lowercase "r".

> +		};
> +	};
>  	void  __percpu **ghcb_base;
> +	u64 shared_gpa_boundary;
>  };
>  extern struct ms_hyperv_info ms_hyperv;
> 
> --
> 2.25.1