Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Wed, 16 Nov 2022 01:56:12 +0000
From:   Sean Christopherson <seanjc@google.com>
To:     "Huang, Kai" <kai.huang@intel.com>
Cc:     "imbrenda@linux.ibm.com" <imbrenda@linux.ibm.com>,
        "aou@eecs.berkeley.edu" <aou@eecs.berkeley.edu>,
        "mjrosato@linux.ibm.com" <mjrosato@linux.ibm.com>,
        "vkuznets@redhat.com" <vkuznets@redhat.com>,
        "farman@linux.ibm.com" <farman@linux.ibm.com>,
        "chenhuacai@kernel.org" <chenhuacai@kernel.org>,
        "paul.walmsley@sifive.com" <paul.walmsley@sifive.com>,
        "palmer@dabbelt.com" <palmer@dabbelt.com>,
        "maz@kernel.org" <maz@kernel.org>,
        "anup@brainfault.org" <anup@brainfault.org>,
        "pbonzini@redhat.com" <pbonzini@redhat.com>,
        "borntraeger@linux.ibm.com" <borntraeger@linux.ibm.com>,
        "aleksandar.qemu.devel@gmail.com" <aleksandar.qemu.devel@gmail.com>,
        "frankja@linux.ibm.com" <frankja@linux.ibm.com>,
        "oliver.upton@linux.dev" <oliver.upton@linux.dev>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "Yao, Yuan" <yuan.yao@intel.com>,
        "farosas@linux.ibm.com" <farosas@linux.ibm.com>,
        "david@redhat.com" <david@redhat.com>,
        "james.morse@arm.com" <james.morse@arm.com>,
        "mpe@ellerman.id.au" <mpe@ellerman.id.au>,
        "alexandru.elisei@arm.com" <alexandru.elisei@arm.com>,
        "linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "Yamahata, Isaku" <isaku.yamahata@intel.com>,
        "kvmarm@lists.linux.dev" <kvmarm@lists.linux.dev>,
        "suzuki.poulose@arm.com" <suzuki.poulose@arm.com>,
        "kvm-riscv@lists.infradead.org" <kvm-riscv@lists.infradead.org>,
        "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-mips@vger.kernel.org" <linux-mips@vger.kernel.org>,
        "kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
        "Gao, Chao" <chao.gao@intel.com>,
        "atishp@atishpatra.org" <atishp@atishpatra.org>,
        "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>
Subject: Re: [PATCH 33/44] KVM: x86: Do VMX/SVM support checks directly in
 vendor code
Message-ID: <Y3RDPOerOIf6SwI0@google.com>
References: <20221102231911.3107438-1-seanjc@google.com>
 <20221102231911.3107438-34-seanjc@google.com>
 <95c3cce88560024566f3b4b0061ca7e62a8a4286.camel@intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <95c3cce88560024566f3b4b0061ca7e62a8a4286.camel@intel.com>
Precedence: bulk

On Tue, Nov 15, 2022, Huang, Kai wrote:
> On Wed, 2022-11-02 at 23:19 +0000, Sean Christopherson wrote:
> > +static bool __init kvm_is_vmx_supported(void)
> > +{
> > +	if (!cpu_has_vmx()) {
> > +		pr_err("CPU doesn't support VMX\n");
> > +		return false;
> > +	}
> > +
> > +	if (!boot_cpu_has(X86_FEATURE_MSR_IA32_FEAT_CTL) ||
> > +	??? !boot_cpu_has(X86_FEATURE_VMX)) {
> > +		pr_err("VMX not enabled in MSR_IA32_FEAT_CTL\n");
> > +		return false;
> > +	}
> > +
> > +	return true;
> > +}
> > +
> > ?static int __init vmx_check_processor_compat(void)
> > ?{
> > ?	struct vmcs_config vmcs_conf;
> > ?	struct vmx_capability vmx_cap;
> > ?
> > -	if (!this_cpu_has(X86_FEATURE_MSR_IA32_FEAT_CTL) ||
> > -	??? !this_cpu_has(X86_FEATURE_VMX)) {
> > -		pr_err("VMX is disabled on CPU %d\n", smp_processor_id());
> > +	if (!kvm_is_vmx_supported())
> > ?		return -EIO;
> > -	}
> > ?
> 
> Looks there's a functional change here -- the old code checks local cpu's
> feature bits but the new code always checks bsp's feature bits.  Should have no
> problem I think, though.

Ouch.  The bad check will defeat the purpose of doing compat checks.  Nice catch!