Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH 3/4] KVM: x86: WARN and reject loading KVM if NX is
 supported but not enabled
To:     Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20210615164535.2146172-1-seanjc@google.com>
 <20210615164535.2146172-4-seanjc@google.com> <YNUITW5fsaQe4JSo@google.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <ad85c5db-c780-bd13-c6ce-e3478838acbe@redhat.com>
Date:   Fri, 25 Jun 2021 11:04:59 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.10.1
MIME-Version: 1.0
In-Reply-To: <YNUITW5fsaQe4JSo@google.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 25/06/21 00:33, Sean Christopherson wrote:
> On Tue, Jun 15, 2021, Sean Christopherson wrote:
>> WARN if NX is reported as supported but not enabled in EFER.  All flavors
>> of the kernel, including non-PAE 32-bit kernels, set EFER.NX=1 if NX is
>> supported, even if NX usage is disable via kernel command line.
> 
> Ugh, I misread .Ldefault_entry in head_32.S, it skips over the entire EFER code
> if PAE=0.  Apparently I didn't test this with non-PAE paging and EPT?
> 
> Paolo, I'll send a revert since it's in kvm/next, but even better would be if
> you can drop the patch :-)  Lucky for me you didn't pick up patch 4/4 that
> depends on this...
> 
> I'll revisit this mess in a few weeks.

Rather, let's keep this, see if anyone complains and possibly add a 
"depends on X86_PAE || X86_64" to KVM.

Paolo