linux-kernel - RE: [PATCH v3] x86/hyper-v: Mark TLFS structures packed

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Message-ID: <CY4PR21MB07731E29CA0BAEE1697690BBD7AE0@CY4PR21MB0773.namprd21.prod.outlook.com>
Date:   Mon, 3 Dec 2018 16:26:02 +0000
From:   Michael Kelley <mikelley@...rosoft.com>
To:     vkuznets <vkuznets@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
CC:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Roman Kagan <rkagan@...tuozzo.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "x86@...nel.org" <x86@...nel.org>,
        Nadav Amit <nadav.amit@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: RE: [PATCH v3] x86/hyper-v: Mark TLFS structures packed

From: Vitaly Kuznetsov <vkuznets@...hat.com>  Sent: Monday, December 3, 2018 6:07 AM
>
> The TLFS structures are used for hypervisor-guest communication and must
> exactly meet the specification.
> 
> Compilers can add alignment padding to structures or reorder struct members
> for randomization and optimization, which would break the hypervisor ABI.
> 
> Mark the structures as packed to prevent this.
> 
> Suggested-by: Nadav Amit <nadav.amit@...il.com>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> Acked-by: Thomas Gleixner <tglx@...utronix.de>
> Acked-by: Nadav Amit <nadav.amit@...il.com>
> ---
> - Changes since v2:
>  - add __packed to struct 'u' defined within union 'hv_port_id'
>    [Michael Kelley]
> 
> - This is a follow-up to my "[PATCH v2 0/4] x86/kvm/hyper-v: Implement
>  Direct Mode for synthetic timers" series, as suggested by Thomas I'm
>  routing it to KVM tree to avoid merge conflicts.
> ---

Reviewed-by: Michael Kelley <mikelley@...rosoft.com>