linux-kernel - Re: [PATCH Part1 RFC v3 06/22] x86/sev: check SEV-SNP features support

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Message-ID: <e617a0a1-bb8d-9d75-56a4-2ac1138ebf8b@amd.com>
Date:   Thu, 17 Jun 2021 13:46:08 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     brijesh.singh@....com, 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>, tony.luck@...el.com,
        npmccallum@...hat.com
Subject: Re: [PATCH Part1 RFC v3 06/22] x86/sev: check SEV-SNP features
 support

Hi Boris,


On 6/7/2021 9:54 AM, Borislav Petkov wrote:
> On Wed, Jun 02, 2021 at 09:04:00AM -0500, Brijesh Singh wrote:
>>  static bool early_setup_sev_es(void)
> 
> This function is doing SNP init now too, so it should be called
> something generic like
> 
> 	do_early_sev_setup()
> 
> or so.
> 
>>  #define GHCB_SEV_ES_GEN_REQ		0
>>  #define GHCB_SEV_ES_PROT_UNSUPPORTED	1
>> +#define GHCB_SEV_ES_SNP_UNSUPPORTED	2
> 
> GHCB_SNP_UNSUPPORTED
> 
>> +static bool __init sev_snp_check_hypervisor_features(void)
> 
> check_hv_features()
> 

Based on your feedback on AP creation patch to not use the accessors, I am inclined to
remove this helper and have the caller directly check the feature bit, is that okay ?

something like:

if (sev_snp_enabled() && !(hv_features & GHCB_HV_FT_SNP))
	sev_es_terminate(GHCB_SNP_UNSUPPORTED);

Let me know if you think I should still keep the accessors.

-Brijesh

> is nice and short.
> 
>> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
>> index 77a754365ba9..9b70b7332614 100644
>> --- a/arch/x86/kernel/sev.c
>> +++ b/arch/x86/kernel/sev.c
>> @@ -609,6 +609,10 @@ static bool __init sev_es_setup_ghcb(void)
> 
> Ditto for this one: setup_ghcb()
> 
> Thx.
>