linux-kernel - Re: [PATCH v19 023/130] KVM: TDX: Initialize the TDX module when loading the KVM intel kernel module

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Message-ID: <5470a429-cbbd-4946-b11a-ab86380d9b68@linux.intel.com>
Date: Fri, 15 Mar 2024 12:44:46 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Isaku Yamahata <isaku.yamahata@...el.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
 isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
 erdemaktas@...gle.com, Sean Christopherson <seanjc@...gle.com>,
 Sagi Shahar <sagis@...gle.com>, Kai Huang <kai.huang@...el.com>,
 chen.bo@...el.com, hang.yuan@...el.com, tina.zhang@...el.com,
 isaku.yamahata@...ux.intel.com
Subject: Re: [PATCH v19 023/130] KVM: TDX: Initialize the TDX module when
 loading the KVM intel kernel module



On 3/15/2024 12:27 AM, Isaku Yamahata wrote:
> On Thu, Mar 14, 2024 at 10:05:35AM +0800,
> Binbin Wu <binbin.wu@...ux.intel.com> wrote:
>
>>> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
>>> index 18cecf12c7c8..18aef6e23aab 100644
>>> --- a/arch/x86/kvm/vmx/main.c
>>> +++ b/arch/x86/kvm/vmx/main.c
>>> @@ -6,6 +6,22 @@
>>>    #include "nested.h"
>>>    #include "pmu.h"
>>> +static bool enable_tdx __ro_after_init;
>>> +module_param_named(tdx, enable_tdx, bool, 0444);
>>> +
>>> +static __init int vt_hardware_setup(void)
>>> +{
>>> +	int ret;
>>> +
>>> +	ret = vmx_hardware_setup();
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	enable_tdx = enable_tdx && !tdx_hardware_setup(&vt_x86_ops);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>>    #define VMX_REQUIRED_APICV_INHIBITS				\
>>>    	(BIT(APICV_INHIBIT_REASON_DISABLE)|			\
>>>    	 BIT(APICV_INHIBIT_REASON_ABSENT) |			\
>>> @@ -22,6 +38,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
>>>    	.hardware_unsetup = vmx_hardware_unsetup,
>>> +	/* TDX cpu enablement is done by tdx_hardware_setup(). */
>> How about if there are some LPs that are offline.
>> In tdx_hardware_setup(), only online LPs are initialed for TDX, right?
> Correct.
>
>
>> Then when an offline LP becoming online, it doesn't have a chance to call
>> tdx_cpu_enable()?
> KVM registers kvm_online/offline_cpu() @ kvm_main.c as cpu hotplug callbacks.
> Eventually x86 kvm hardware_enable() is called on online/offline event.

Yes, hardware_enable() will be called when online,
but  hardware_enable() now is vmx_hardware_enable() right?
It doens't call tdx_cpu_enable() during the online path.