linux-kernel - Re: [PATCH v2 12/14] KVM: SVM: Drop redundant svm_sev

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Message-ID: <bfce6e5e-2edd-cbd2-79e5-737e66da20f3@amd.com>
Date:   Thu, 14 Jan 2021 16:51:29 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Borislav Petkov <bp@...e.de>,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH v2 12/14] KVM: SVM: Drop redundant svm_sev_enabled()
 helper

On 1/13/21 6:37 PM, Sean Christopherson wrote:
> Replace calls to svm_sev_enabled() with direct checks on sev_enabled, or
> in the case of svm_mem_enc_op, simply drop the call to svm_sev_enabled().
> This effectively replaces checks against a valid max_sev_asid with checks
> against sev_enabled.  sev_enabled is forced off by sev_hardware_setup()
> if max_sev_asid is invalid, all call sites are guaranteed to run after
> sev_hardware_setup(), and all of the checks care about SEV being fully
> enabled (as opposed to intentionally handling the scenario where
> max_sev_asid is valid but SEV enabling fails due to OOM).
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Ultimately the #ifdef CONFIG_KVM_AMD_SEV that you added that #defines 
sev_enabled and sev_es_enabled to false, resolves the build issue when 
kvm_amd is built into the kernel and ccp is built as a module, for which 
svm_sev_enabled() was originally created.

Reviewed-by: Tom Lendacky <thomas.lendacky@....com>

> ---
>   arch/x86/kvm/svm/sev.c | 6 +++---
>   arch/x86/kvm/svm/svm.h | 5 -----
>   2 files changed, 3 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index a2c3e2d42a7f..7e14514dd083 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1057,7 +1057,7 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
>   	struct kvm_sev_cmd sev_cmd;
>   	int r;
>   
> -	if (!svm_sev_enabled() || !sev_enabled)
> +	if (!sev_enabled)
>   		return -ENOTTY;
>   
>   	if (!argp)
> @@ -1321,7 +1321,7 @@ void __init sev_hardware_setup(void)
>   
>   void sev_hardware_teardown(void)
>   {
> -	if (!svm_sev_enabled())
> +	if (!sev_enabled)
>   		return;
>   
>   	bitmap_free(sev_asid_bitmap);
> @@ -1332,7 +1332,7 @@ void sev_hardware_teardown(void)
>   
>   int sev_cpu_init(struct svm_cpu_data *sd)
>   {
> -	if (!svm_sev_enabled())
> +	if (!sev_enabled)
>   		return 0;
>   
>   	sd->sev_vmcbs = kmalloc_array(max_sev_asid + 1, sizeof(void *),
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index 4eb4bab0ca3e..8cb4395b58a0 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -569,11 +569,6 @@ void svm_vcpu_unblocking(struct kvm_vcpu *vcpu);
>   
>   extern unsigned int max_sev_asid;
>   
> -static inline bool svm_sev_enabled(void)
> -{
> -	return IS_ENABLED(CONFIG_KVM_AMD_SEV) ? max_sev_asid : 0;
> -}
> -
>   void sev_vm_destroy(struct kvm *kvm);
>   int svm_mem_enc_op(struct kvm *kvm, void __user *argp);
>   int svm_register_enc_region(struct kvm *kvm,
>