linux-kernel - Re: [PATCH v6 07/42] x86/sev: Add support for hypervisor feature VMGEXIT

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Date:   Wed, 13 Oct 2021 16:02:33 +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,
        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>,
        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>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH v6 07/42] x86/sev: Add support for hypervisor feature
 VMGEXIT

On Fri, Oct 08, 2021 at 01:04:18PM -0500, Brijesh Singh wrote:
> Version 2 of GHCB specification introduced advertisement of a features
> that are supported by the hypervisor. Add support to query the HV
> features on boot.
> 
> Version 2 of GHCB specification adds several new NAEs, most of them are
> optional except the hypervisor feature. Now that hypervisor feature NAE
> is implemented, so bump the GHCB maximum support protocol version.
> 
> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
> ---
>  arch/x86/include/asm/sev-common.h |  3 +++
>  arch/x86/include/asm/sev.h        |  2 +-
>  arch/x86/include/uapi/asm/svm.h   |  2 ++
>  arch/x86/kernel/sev-shared.c      | 30 ++++++++++++++++++++++++++++++
>  4 files changed, 36 insertions(+), 1 deletion(-)

For the next version, when you add those variables, do this too pls:

diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index 8ee27d07c1cd..7a2176e0d0ad 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -21,10 +21,10 @@
  *
  * GHCB protocol version negotiated with the hypervisor.
  */
-static u16 __ro_after_init ghcb_version;
+static u16 ghcb_version __ro_after_init;
 
 /* Bitmap of SEV features supported by the hypervisor */
-static u64 __ro_after_init sev_hv_features;
+static u64 sev_hv_features __ro_after_init;
 
 static bool __init sev_es_check_cpu_features(void)
 {

I didn't realize this earlier but we put that annotation at the end.

Thx.

-- 
Regards/Gruss,
    Boris.

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