linux-kernel - Re: [PATCH Part1 RFC v4 03/36] x86/sev: Add support for hypervisor feature VMGEXIT

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Date:   Tue, 10 Aug 2021 13:22:19 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-crypto@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Dov Murik <dovmurik@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>, tony.luck@...el.com,
        npmccallum@...hat.com, brijesh.ksingh@...il.com
Subject: Re: [PATCH Part1 RFC v4 03/36] x86/sev: Add support for hypervisor
 feature VMGEXIT

On Wed, Jul 07, 2021 at 01:14:33PM -0500, Brijesh Singh wrote:
> diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
> index 11b7d9cea775..23929a3010df 100644
> --- a/arch/x86/include/asm/sev-common.h
> +++ b/arch/x86/include/asm/sev-common.h
> @@ -45,6 +45,15 @@
>  		(((unsigned long)reg & GHCB_MSR_CPUID_REG_MASK) << GHCB_MSR_CPUID_REG_POS) | \
>  		(((unsigned long)fn) << GHCB_MSR_CPUID_FUNC_POS))
>  
> +/* GHCB Hypervisor Feature Request */
> +#define GHCB_MSR_HV_FT_REQ	0x080
> +#define GHCB_MSR_HV_FT_RESP	0x081
> +#define GHCB_MSR_HV_FT_POS	12
> +#define GHCB_MSR_HV_FT_MASK	GENMASK_ULL(51, 0)
> +
> +#define GHCB_MSR_HV_FT_RESP_VAL(v)	\
> +	(((unsigned long)((v) >> GHCB_MSR_HV_FT_POS) & GHCB_MSR_HV_FT_MASK))

As I suggested...

> @@ -215,6 +216,7 @@
>  	{ SVM_VMGEXIT_NMI_COMPLETE,	"vmgexit_nmi_complete" }, \
>  	{ SVM_VMGEXIT_AP_HLT_LOOP,	"vmgexit_ap_hlt_loop" }, \
>  	{ SVM_VMGEXIT_AP_JUMP_TABLE,	"vmgexit_ap_jump_table" }, \
> +	{ SVM_VMGEXIT_HYPERVISOR_FEATURES,	"vmgexit_hypervisor_feature" }, \

	SVM_VMGEXIT_HV_FEATURES

>  	{ SVM_EXIT_ERR,         "invalid_guest_state" }
>  
>  
> diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
> index 19c2306ac02d..34821da5f05e 100644
> --- a/arch/x86/kernel/sev-shared.c
> +++ b/arch/x86/kernel/sev-shared.c
> @@ -23,6 +23,9 @@
>   */
>  static u16 ghcb_version __section(".data..ro_after_init");
>  
> +/* Bitmap of SEV features supported by the hypervisor */
> +u64 sev_hv_features __section(".data..ro_after_init") = 0;

__ro_after_init

> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
> index 66b7f63ad041..540b81ac54c9 100644
> --- a/arch/x86/kernel/sev.c
> +++ b/arch/x86/kernel/sev.c
> @@ -96,6 +96,9 @@ struct ghcb_state {
>  static DEFINE_PER_CPU(struct sev_es_runtime_data*, runtime_data);
>  DEFINE_STATIC_KEY_FALSE(sev_es_enable_key);
>  
> +/* Bitmap of SEV features supported by the hypervisor */
> +EXPORT_SYMBOL(sev_hv_features);

Why is this exported and why not a _GPL export?

-- 
Regards/Gruss,
    Boris.

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