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References: <20190815172237.10464-1-sean.j.christopherson@intel.com>
In-Reply-To: <20190815172237.10464-1-sean.j.christopherson@intel.com>
From:   Jim Mattson <jmattson@google.com>
Date:   Fri, 16 Aug 2019 11:25:05 -0700
Message-ID: <CALMp9eQZ=c4nkKmJQr4omdCmB=P1Yug+g_XK_fqZ0YZuEt0Pkg@mail.gmail.com>
Subject: Re: [PATCH] KVM: Assert that struct kvm_vcpu is always as offset zero
To:     Sean Christopherson <sean.j.christopherson@intel.com>
Cc:     Paul Mackerras <paulus@ozlabs.org>, Joerg Roedel <joro@8bytes.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        kvm-ppc@vger.kernel.org, kvm list <kvm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Thu, Aug 15, 2019 at 10:23 AM Sean Christopherson
<sean.j.christopherson@intel.com> wrote:
>
> KVM implementations that wrap struct kvm_vcpu with a vendor specific
> struct, e.g. struct vcpu_vmx, must place the vcpu member at offset 0,
> otherwise the usercopy region intended to encompass struct kvm_vcpu_arch
> will instead overlap random chunks of the vendor specific struct.
> E.g. padding a large number of bytes before struct kvm_vcpu triggers
> a usercopy warn when running with CONFIG_HARDENED_USERCOPY=y.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
X86 parts:
Reviewed-by: Jim Mattson <jmattson@google.com>