Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Vitaly Kuznetsov <vkuznets@redhat.com>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
        Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        linux-kernel@vger.kernel.org, Roman Kagan <rkagan@virtuozzo.com>,
        "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>, x86@kernel.org,
        "Michael Kelley \(EOSG\)" <Michael.H.Kelley@microsoft.com>,
        Nadav Amit <nadav.amit@gmail.com>
Subject: Re: [PATCH] x86/hyper-v: define structures from TLFS as packed
In-Reply-To: <alpine.DEB.2.21.1811301320410.17702@nanos.tec.linutronix.de>
References: <20181130121511.12331-1-vkuznets@redhat.com> <alpine.DEB.2.21.1811301320410.17702@nanos.tec.linutronix.de>
Date:   Fri, 30 Nov 2018 13:49:52 +0100
Message-ID: <87y39awwzz.fsf@vitty.brq.redhat.com>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Thomas Gleixner <tglx@linutronix.de> writes:

> On Fri, 30 Nov 2018, Vitaly Kuznetsov wrote:
>
>> Subject: x86/hyper-v: define structures from TLFS as packed
>
> Please start the first word after the prefix colon with an uppercase
> letter. Also structures from TLFS doesn't make sense to me. Something like
> this:
>
> Subject: x86/hyper-v: Mark TLFS structures packed
>
>> Without 'packed' compiler is free to add optimization paddings and re-order
>> structure fields for randomization/optimization. And structures from
>
> s/And/As/ ?
>
>> hyperv-tlfs.h are used for hypervisor-guest communication, we need to
>> ultimately forbid such practices.
>
> That whole paragraph reads a bit strange. Something like:
>
>   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.
>
> Hmm?

Sure, will do v2!

>
>> Suggested-by: Nadav Amit <nadav.amit@gmail.com>
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>
> Other than that: Acked-by: Thomas Gleixner <tglx@linutronix.de>

Thanks!

-- 
Vitaly