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From:   "Michael Kelley (LINUX)" <mikelley@microsoft.com>
To:     Tianyu Lan <ltykernel@gmail.com>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        "wei.liu@kernel.org" <wei.liu@kernel.org>,
        Dexuan Cui <decui@microsoft.com>,
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        "bp@alien8.de" <bp@alien8.de>,
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        "daniel.lezcano@linaro.org" <daniel.lezcano@linaro.org>,
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CC:     Tianyu Lan <Tianyu.Lan@microsoft.com>,
        "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "vkuznets@redhat.com" <vkuznets@redhat.com>
Subject: RE: [PATCH 1/9] x86/hyperv: Add sev-snp enlightened guest static key
Thread-Topic: [PATCH 1/9] x86/hyperv: Add sev-snp enlightened guest static key
Thread-Index: AQHZlJwMbcDLsoSDQ0+wxKbSaonMLa+A5piA
Date:   Thu, 8 Jun 2023 12:56:12 +0000
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References: <20230601151624.1757616-1-ltykernel@gmail.com>
 <20230601151624.1757616-2-ltykernel@gmail.com>
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From: Tianyu Lan <ltykernel@gmail.com> Sent: Thursday, June 1, 2023 8:16 AM
>=20
> Introduce static key isolation_type_en_snp for enlightened
> sev-snp guest check.
>=20
> Signed-off-by: Tianyu Lan <tiala@microsoft.com>
> ---
>  arch/x86/hyperv/ivm.c           | 11 +++++++++++
>  arch/x86/include/asm/mshyperv.h |  3 +++
>  arch/x86/kernel/cpu/mshyperv.c  |  8 ++++++--
>  drivers/hv/hv_common.c          |  6 ++++++
>  include/asm-generic/mshyperv.h  | 12 +++++++++---
>  5 files changed, 35 insertions(+), 5 deletions(-)
>=20
> diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
> index cc92388b7a99..5d3ee3124e00 100644
> --- a/arch/x86/hyperv/ivm.c
> +++ b/arch/x86/hyperv/ivm.c
> @@ -409,3 +409,14 @@ bool hv_isolation_type_snp(void)
>  {
>  	return static_branch_unlikely(&isolation_type_snp);
>  }
> +
> +DEFINE_STATIC_KEY_FALSE(isolation_type_en_snp);
> +/*
> + * hv_isolation_type_en_snp - Check system runs in the AMD SEV-SNP based
> + * isolation enlightened VM.
> + */
> +bool hv_isolation_type_en_snp(void)
> +{
> +	return static_branch_unlikely(&isolation_type_en_snp);
> +}
> +
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyp=
erv.h
> index 49bb4f2bd300..31c476f4e656 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -26,6 +26,7 @@
>  union hv_ghcb;
>=20
>  DECLARE_STATIC_KEY_FALSE(isolation_type_snp);
> +DECLARE_STATIC_KEY_FALSE(isolation_type_en_snp);
>=20
>  typedef int (*hyperv_fill_flush_list_func)(
>  		struct hv_guest_mapping_flush_list *flush,
> @@ -45,6 +46,8 @@ extern void *hv_hypercall_pg;
>=20
>  extern u64 hv_current_partition_id;
>=20
> +extern bool hv_isolation_type_en_snp(void);
> +
>  extern union hv_ghcb * __percpu *hv_ghcb_pg;
>=20
>  int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages);
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyper=
v.c
> index c7969e806c64..9186453251f7 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -402,8 +402,12 @@ static void __init ms_hyperv_init_platform(void)
>  		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);
>=20
> -		if (hv_get_isolation_type() =3D=3D HV_ISOLATION_TYPE_SNP)
> +
> +		if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) {
> +			static_branch_enable(&isolation_type_en_snp);
> +		} else if (hv_get_isolation_type() =3D=3D HV_ISOLATION_TYPE_SNP) {
>  			static_branch_enable(&isolation_type_snp);
> +		}
>  	}
>=20
>  	if (hv_max_functions_eax >=3D HYPERV_CPUID_NESTED_FEATURES) {
> @@ -473,7 +477,7 @@ static void __init ms_hyperv_init_platform(void)
>=20
>  #if IS_ENABLED(CONFIG_HYPERV)
>  	if ((hv_get_isolation_type() =3D=3D HV_ISOLATION_TYPE_VBS) ||
> -	    (hv_get_isolation_type() =3D=3D HV_ISOLATION_TYPE_SNP))
> +	    ms_hyperv.paravisor_present)

This test needs to be:

  	if ((hv_get_isolation_type() =3D=3D HV_ISOLATION_TYPE_VBS) ||
	    ((hv_get_isolation_type() =3D=3D HV_ISOLATION_TYPE_SNP) &&
	    ms_hyperv.paravisor_present)

We want to call hv_vtom_init() only when running with VBS, or
with SEV-SNP *and* we have a paravisor present.  Testing only for
paravisor_present risks confusion with future TDX scenarios.

>  		hv_vtom_init();
>  	/*
>  	 * Setup the hook to get control post apic initialization.
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index 64f9ceca887b..179bc5f5bf52 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -502,6 +502,12 @@ bool __weak hv_isolation_type_snp(void)
>  }
>  EXPORT_SYMBOL_GPL(hv_isolation_type_snp);
>=20
> +bool __weak hv_isolation_type_en_snp(void)
> +{
> +	return false;
> +}
> +EXPORT_SYMBOL_GPL(hv_isolation_type_en_snp);
> +
>  void __weak hv_setup_vmbus_handler(void (*handler)(void))
>  {
>  }
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyper=
v.h
> index 402a8c1c202d..d444f831d633 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -36,15 +36,21 @@ struct ms_hyperv_info {
>  	u32 nested_features;
>  	u32 max_vp_index;
>  	u32 max_lp_index;
> -	u32 isolation_config_a;
> +	union {
> +		u32 isolation_config_a;
> +		struct {
> +			u32 paravisor_present : 1;
> +			u32 reserved1 : 31;
> +		};
> +	};
>  	union {
>  		u32 isolation_config_b;
>  		struct {
>  			u32 cvm_type : 4;
> -			u32 reserved1 : 1;
> +			u32 reserved2 : 1;
>  			u32 shared_gpa_boundary_active : 1;
>  			u32 shared_gpa_boundary_bits : 6;
> -			u32 reserved2 : 20;
> +			u32 reserved3 : 20;
>  		};
>  	};
>  	u64 shared_gpa_boundary;
> --
> 2.25.1