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From: Hao Xiang <hao.xiang@linux.alibaba.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
	Xiaoyao Li <xiaoyao.li@intel.com>,
	kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, chenyi.qiang@intel.com,
	shannon.zhao@linux.alibaba.com,
	Sean Christopherson <seanjc@google.com>,
	hao.xiang@linux.alibaba.com
Subject: Re: [PATCH] KVM: VMX: Check if bus lock vmexit was preempted
Date: Thu, 23 Sep 2021 08:59:11 +0800	[thread overview]
Message-ID: <84cd2713-3cc4-3120-946e-0cf8b8a8187d@linux.alibaba.com> (raw)
In-Reply-To: <a0d6bcd8-11e4-4efd-0317-0bec6e59f06a@redhat.com>


On 2021/9/22 20:40, Paolo Bonzini wrote:
> On 22/09/21 12:32, Xiaoyao Li wrote:
>>>
>>
>> EXIT_REASON.bus_lock_detected may or may not be set when exit reason 
>> == EXIT_REASON_BUS_LOCK. Intel will update ISE or SDM to state it.
>>
>> Maybe we can do below in handle_bus_lock_vmexit handler:
>>
>>      if (!to_vmx(vcpu)->exit_reason.bus_lock_detected)
>>          to_vmx(vcpu)->exit_reason.bus_lock_detected = 1;
>>
>> But is manually changing the hardware reported value for software 
>> purpose a good thing?
>
> No.  That said, Hao's patch is just making the code clearer; there's 
> no behavioral change since the "if" will just redo the same 
> assignments as handle_bus_lock_vmexit.
>
> Paolo
I agree Paolo. EXIT_REASON.bus_lock_detected may or may not be set when 
exit_reason=EXIT_REASON_BUS_LOCK,  It clould depend on hardware 
implementaion. No matter when intel states it clearly, I think it is 
better that we avoid repeated assignment by adding additional check 
condition in vmx_handle_exit.  Of course , it is also ok that 
hand_bus_lock_vmexit do nothing , but the code is not clear, and the 
code logic will be inconsistent with spec description.

  reply	other threads:[~2021-09-23  0:59 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-18 11:30 [PATCH] KVM: VMX: Check if bus lock vmexit was preempted Hao Xiang
2021-09-22 10:02 ` Paolo Bonzini
2021-09-22 10:32   ` Xiaoyao Li
2021-09-22 12:40     ` Paolo Bonzini
2021-09-23  0:59       ` Hao Xiang [this message]
2021-09-23  6:37         ` Paolo Bonzini
2021-09-22 14:58     ` Sean Christopherson
2021-09-23  7:15       ` Hao Xiang

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