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From: Paolo Bonzini <pbonzini@redhat.com>
To: "Kang, Luwei" <luwei.kang@intel.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Cc: "rkrcmar@redhat.com" <rkrcmar@redhat.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"hpa@zytor.com" <hpa@zytor.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Chao Peng <chao.p.peng@linux.intel.com>
Subject: Re: [patch v2 3/8] KVM: x86: add Intel processor trace virtualization mode
Date: Tue, 14 Nov 2017 11:47:22 +0100	[thread overview]
Message-ID: <de621c4c-6116-2340-428b-ad3e03151752@redhat.com> (raw)
In-Reply-To: <82D7661F83C1A047AF7DC287873BF1E167E37638@SHSMSX101.ccr.corp.intel.com>

On 14/11/2017 08:31, Kang, Luwei wrote:
>>> +	if (!(_cpu_based_2nd_exec_control & SECONDARY_EXEC_PT_USE_GPA) ||
>>> +		!(_vmexit_control & VM_EXIT_CLEAR_IA32_RTIT_CTL) ||
>>> +		!(_vmentry_control & VM_ENTRY_LOAD_IA32_RTIT_CTL)) {
>>> +		_cpu_based_2nd_exec_control &= ~SECONDARY_EXEC_PT_USE_GPA;
>>
>> Also, you are not checking anywhere if the SUPPRESS_PIP controls are available.  This is probably the best place.
> 
> SUPPRESS_PIP(should be "CONCEAL", will fix it.) is use for control of  processor trace packet. 
> I think we should clear it when in SYSTEM mode (For example, PIPs are
> generated on VM exit, with NonRoot=0. On VM exit to SMM, VMCS packets
> are additionally generated). Why need check this here?

I agree.  But if SUPPRESS_PIP/CONCEAL is not available, you cannot
enable HOST_GUEST mode I think?

>>
>>> +		_vmexit_control &= ~VM_EXIT_CLEAR_IA32_RTIT_CTL;
>>> +		_vmentry_control &= ~VM_ENTRY_LOAD_IA32_RTIT_CTL;
>>
>> These two are not needed; disabling SECONDARY_EXEC_PT_USE_GPA is enough.
>> The tracing mode will revert to PT_SYSTEM, which does not use the load/clear RTIT_CTL controls.
> 
> The status of *_RTIT_CTL should be same with SECONDARY_EXEC_PT_USE_GPA
> or would cause VM-entry failed.
> (architecture-instruction-set-extensions-programming-reference 5.2.3)

Indeed:

- disable "use GPA" here

- hardware_setup notices !cpu_has_vmx_pt_use_gpa() and switches tracing
mode to system

- vmx_vcpu_setup (via vmx_vmentry_control and vmx_vmexit_control) turns
off the IA32_RIT_CTL vmentry/vmexit controls (and also turns off
SUPPRESS_PIP)

- everybody is happy

Paolo

  reply	other threads:[~2017-11-14 10:47 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-30 22:05 [patch v2 0/8] Intel Processor Trace virtulization enabling Luwei Kang
2017-10-30 22:05 ` [patch v2 1/8] perf/x86/intel/pt: Move Intel-PT MSR bit definitions to a public header Luwei Kang
2017-10-30 22:05 ` [patch v2 2/8] perf/x86/intel/pt: change pt_cap_get() to a public function Luwei Kang
2017-10-30 22:05 ` [patch v2 3/8] KVM: x86: add Intel processor trace virtualization mode Luwei Kang
2017-11-13 16:29   ` Paolo Bonzini
2017-11-14  7:11     ` Kang, Luwei
2017-11-13 16:32   ` Paolo Bonzini
2017-11-14  7:31     ` Kang, Luwei
2017-11-14 10:47       ` Paolo Bonzini [this message]
2017-10-30 22:05 ` [patch v2 4/8] KVM: x86: add Intel processor trace cpuid emulataion Luwei Kang
2017-11-13 15:36   ` Paolo Bonzini
2017-11-14  2:56     ` Kang, Luwei
2017-10-30 22:05 ` [patch v2 5/8] KVM: x86: add Intel processor trace context for each vcpu Luwei Kang
2017-10-30 22:05 ` [patch v2 6/8] KVM: x86: Implement Intel processor trace context switch Luwei Kang
2017-11-13 16:01   ` Paolo Bonzini
2017-10-30 22:05 ` [patch v2 7/8] KVM: x86: add Intel PT msr RTIT_CTL read/write Luwei Kang
2017-11-13 16:22   ` Paolo Bonzini
2017-11-14  6:59     ` Kang, Luwei
2017-11-14 10:34       ` Paolo Bonzini
2017-10-30 22:05 ` [patch v2 8/8] KVM: x86: Disable intercept for Intel processor trace MSRs Luwei Kang
2017-11-13 16:24   ` Paolo Bonzini
2017-11-14  7:01     ` Kang, Luwei
2017-11-02 14:57 ` [patch v2 0/8] Intel Processor Trace virtulization enabling Paolo Bonzini
2017-11-03  6:09   ` Kang, Luwei

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