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:   Tue, 30 May 2023 10:14:15 -0700
In-Reply-To: <20230530215036.000066d9.zhi.wang.linux@gmail.com>
Mime-Version: 1.0
References: <cover.1685333727.git.isaku.yamahata@intel.com>
 <e628e2d235d9b6c00b9bd5d81bb69136b77d13c4.1685333727.git.isaku.yamahata@intel.com>
 <20230530215036.000066d9.zhi.wang.linux@gmail.com>
Message-ID: <ZHYu5yvtw7oMDUAP@google.com>
Subject: Re: [PATCH v14 004/113] KVM: TDX: Initialize the TDX module when
 loading the KVM intel kernel module
From:   Sean Christopherson <seanjc@google.com>
To:     Zhi Wang <zhi.wang.linux@gmail.com>
Cc:     isaku.yamahata@intel.com, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, isaku.yamahata@gmail.com,
        Paolo Bonzini <pbonzini@redhat.com>, erdemaktas@google.com,
        Sagi Shahar <sagis@google.com>,
        David Matlack <dmatlack@google.com>,
        Kai Huang <kai.huang@intel.com>, chen.bo@intel.com
Content-Type: text/plain; charset="us-ascii"
Precedence: bulk

On Tue, May 30, 2023, Zhi Wang wrote:
> On Sun, 28 May 2023 21:18:46 -0700 isaku.yamahata@intel.com wrote:
> > +	/* tdx_enable() in tdx_module_setup() requires cpus lock. */
> > +	cpus_read_lock();
> > +	on_each_cpu(vmx_tdx_on, &err, true);	/* TDX requires vmxon. */
> > +	r = atomic_read(&err);
> > +	if (!r)
> > +		r = tdx_module_setup();
> > +	on_each_cpu(vmx_off, NULL, true);
> 
> Out of curiosity, why VMX has to be turned off after tdx_module_setup()?

KVM has historically enabled VMX if and only if KVM has active VMs.  Whether or
not it still makes sense to do dynamic enabling is debatable, but that's a
discussion for another day.