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Subject: Re: [patch v2 3/8] KVM: x86: add Intel processor trace virtualization
 mode
To: Luwei Kang <luwei.kang@intel.com>, kvm@vger.kernel.org
Cc: rkrcmar@redhat.com, tglx@linutronix.de, mingo@redhat.com,
        hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org,
        Chao Peng <chao.p.peng@linux.intel.com>
References: <1509401117-15521-1-git-send-email-luwei.kang@intel.com>
 <1509401117-15521-4-git-send-email-luwei.kang@intel.com>
From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <9838721f-ed64-cec8-f3dc-895c0bb7a681@redhat.com>
Date: Mon, 13 Nov 2017 17:32:00 +0100
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On 30/10/2017 23:05, Luwei Kang 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.

> +		_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.

Paolo

> +	}
> +