linux-kernel - Re: [PATCH v19 087/130] KVM: TDX: handle vcpu migration over logical processor

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Message-ID: <01988152-c87b-4814-adc5-618e31fc035e@linux.intel.com>
Date: Tue, 23 Apr 2024 20:13:25 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Reinette Chatre <reinette.chatre@...el.com>, 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
Subject: Re: [PATCH v19 087/130] KVM: TDX: handle vcpu migration over logical
 processor



On 4/13/2024 12:15 AM, Reinette Chatre wrote:
> Hi Isaku,
>
> On 2/26/2024 12:26 AM, isaku.yamahata@...el.com wrote:
>> From: Isaku Yamahata <isaku.yamahata@...el.com>
> ...
>
>> @@ -218,6 +257,87 @@ static void tdx_reclaim_control_page(unsigned long td_page_pa)
>>   	free_page((unsigned long)__va(td_page_pa));
>>   }
>>   
>> +struct tdx_flush_vp_arg {
>> +	struct kvm_vcpu *vcpu;
>> +	u64 err;
>> +};
>> +
>> +static void tdx_flush_vp(void *arg_)
>> +{
>> +	struct tdx_flush_vp_arg *arg = arg_;
>> +	struct kvm_vcpu *vcpu = arg->vcpu;
>> +	u64 err;
>> +
>> +	arg->err = 0;
>> +	lockdep_assert_irqs_disabled();
>> +
>> +	/* Task migration can race with CPU offlining. */
>> +	if (unlikely(vcpu->cpu != raw_smp_processor_id()))
>> +		return;
>> +
>> +	/*
>> +	 * No need to do TDH_VP_FLUSH if the vCPU hasn't been initialized.  The
>> +	 * list tracking still needs to be updated so that it's correct if/when
>> +	 * the vCPU does get initialized.
>> +	 */
>> +	if (is_td_vcpu_created(to_tdx(vcpu))) {
>> +		/*
>> +		 * No need to retry.  TDX Resources needed for TDH.VP.FLUSH are,
>> +		 * TDVPR as exclusive, TDR as shared, and TDCS as shared.  This
>> +		 * vp flush function is called when destructing vcpu/TD or vcpu
>> +		 * migration.  No other thread uses TDVPR in those cases.
>> +		 */
Is it possible that other thread uses TDR or TDCS as exclusive?

>>