linux-kernel - Re: [PATCH 5/5] KVM: x86/xen: Explicitly pad struct compat_vcpu

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Message-ID: <9dbfbc342899895a13effb7ed745001549b51798.camel@amazon.co.uk>
Date:   Wed, 10 Feb 2021 21:20:08 +0000
From:   "Woodhouse, David" <dwmw@...zon.co.uk>
To:     "seanjc@...gle.com" <seanjc@...gle.com>
CC:     "jmattson@...gle.com" <jmattson@...gle.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "wanpengli@...cent.com" <wanpengli@...cent.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/5] KVM: x86/xen: Explicitly pad struct compat_vcpu_info to 64
 bytes

On Wed, 2021-02-10 at 13:13 -0800, Sean Christopherson wrote:
> On Wed, Feb 10, 2021, Woodhouse, David wrote:
> > On Wed, 2021-02-10 at 10:26 -0800, Sean Christopherson wrote:
> > So it isn't clear the additionally padding really buys us anything; if
> > we play this game without knowing the ABI we'd be screwed anyway. But
> > it doesn't hurt.
> 
> Ya, this is purely for folks reading the code and wondering how 62==64.

Fair enough. That kind of thing is why I littered the code with
assertions based on sizeof() and offsetof() :)



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