linux-kernel - Re: [PATCH v4 6/6] KVM: SVM: Delay legacy platform initialization on SNP

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Message-ID: <3f60b8cc-1075-be41-eb31-f802cac0d315@amd.com>
Date: Wed, 6 Nov 2024 08:45:15 -0600
From: Tom Lendacky <thomas.lendacky@....com>
To: Dionna Glaze <dionnaglaze@...gle.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org, Sean Christopherson <seanjc@...gle.com>,
 Paolo Bonzini <pbonzini@...hat.com>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>
Cc: Ashish Kalra <ashish.kalra@....com>, John Allen <john.allen@....com>,
 Herbert Xu <herbert@...dor.apana.org.au>,
 "David S. Miller" <davem@...emloft.net>, Michael Roth
 <michael.roth@....com>, Luis Chamberlain <mcgrof@...nel.org>,
 Russ Weight <russ.weight@...ux.dev>, Danilo Krummrich <dakr@...hat.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>,
 Tianfei zhang <tianfei.zhang@...el.com>, Alexey Kardashevskiy <aik@....com>,
 kvm@...r.kernel.org
Subject: Re: [PATCH v4 6/6] KVM: SVM: Delay legacy platform initialization on
 SNP

On 11/4/24 19:05, Dionna Glaze wrote:
> When no SEV or SEV-ES guests are active, then the firmware can be
> updated while (SEV-SNP) VM guests are active.
> 
> CC: Sean Christopherson <seanjc@...gle.com>
> CC: Paolo Bonzini <pbonzini@...hat.com>
> CC: Thomas Gleixner <tglx@...utronix.de>
> CC: Ingo Molnar <mingo@...hat.com>
> CC: Borislav Petkov <bp@...en8.de>
> CC: Dave Hansen <dave.hansen@...ux.intel.com>
> CC: Ashish Kalra <ashish.kalra@....com>
> CC: Tom Lendacky <thomas.lendacky@....com>
> CC: John Allen <john.allen@....com>
> CC: Herbert Xu <herbert@...dor.apana.org.au>
> CC: "David S. Miller" <davem@...emloft.net>
> CC: Michael Roth <michael.roth@....com>
> CC: Luis Chamberlain <mcgrof@...nel.org>
> CC: Russ Weight <russ.weight@...ux.dev>
> CC: Danilo Krummrich <dakr@...hat.com>
> CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> CC: "Rafael J. Wysocki" <rafael@...nel.org>
> CC: Tianfei zhang <tianfei.zhang@...el.com>
> CC: Alexey Kardashevskiy <aik@....com>
> 
> Co-developed-by: Ashish Kalra <ashish.kalra@....com>
> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> Reviewed-by: Ashish Kalra <ashish.kalra@....com>
> Signed-off-by: Dionna Glaze <dionnaglaze@...gle.com>
> ---
>  arch/x86/kvm/svm/sev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index f6e96ec0a5caa..3c2079ba7c76f 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -444,7 +444,7 @@ static int __sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp,
>  	if (ret)
>  		goto e_no_asid;
>  
> -	init_args.probe = false;
> +	init_args.probe = vm_type != KVM_X86_SEV_VM && vm_type != KVM_X86_SEV_ES_VM;

Add a comment above the setting of probe to indicate the intent of doing
this. Otherwise you have to go to the ccp code to understand what is
happening.

Thanks,
Tom

>  	ret = sev_platform_init(&init_args);
>  	if (ret)
>  		goto e_free;