linux-kernel - Re: [PATCH Part1 v5 13/38] x86/sev: Register GHCB memory when SEV-SNP is active

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Date:   Mon, 23 Aug 2021 13:56:06 -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,
        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>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>, tony.luck@...el.com,
        marcorr@...gle.com, sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH Part1 v5 13/38] x86/sev: Register GHCB memory when SEV-SNP
 is active



On 8/23/21 12:35 PM, Borislav Petkov wrote:
> On Fri, Aug 20, 2021 at 10:19:08AM -0500, Brijesh Singh wrote:
>> The SEV-SNP guest is required to perform GHCB GPA registration. This is
>> because the hypervisor may prefer that a guest use a consistent and/or
>> specific GPA for the GHCB associated with a vCPU. For more information,
>> see the GHCB specification section GHCB GPA Registration.
>>
>> During the boot, init_ghcb() allocates a per-cpu GHCB page. On very first
>> VC exception, the exception handler switch to using the per-cpu GHCB page
>> allocated during the init_ghcb(). The GHCB page must be registered in
>> the current vcpu context.
>>
>> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
>> ---
>>   arch/x86/kernel/sev-internal.h | 12 ++++++++++++
>>   arch/x86/kernel/sev.c          | 28 ++++++++++++++++++++++++++++
>>   2 files changed, 40 insertions(+)
>>   create mode 100644 arch/x86/kernel/sev-internal.h
>>
>> diff --git a/arch/x86/kernel/sev-internal.h b/arch/x86/kernel/sev-internal.h
>> new file mode 100644
>> index 000000000000..0fb7324803b4
>> --- /dev/null
>> +++ b/arch/x86/kernel/sev-internal.h
>> @@ -0,0 +1,12 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * Forward declarations for sev-shared.c
>> + *
>> + * Author: Brijesh Singh <brijesh.singh@....com>
>> + */
>> +
>> +#ifndef __X86_SEV_INTERNAL_H__
>> +
>> +static void snp_register_ghcb_early(unsigned long paddr);
>> +
>> +#endif	/* __X86_SEV_INTERNAL_H__ */
> 
> I believe you don't need that header if you move __sev_get_ghcb()
> and snp_register_ghcb() under the #include "sev-shared.c" so that
> snp_register_ghcb_early() is visible by then.
> 

thanks, I will merge this in next version.