From: Alexander Shishkin <alexander.shishkin@linux.intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
Luwei Kang <luwei.kang@intel.com>,
kvm@vger.kernel.org, x86@kernel.org
Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
hpa@zytor.com, rkrcmar@redhat.com, joro@8bytes.org,
songliubraving@fb.com, peterz@infradead.org,
kstewart@linuxfoundation.org, gregkh@linuxfoundation.org,
thomas.lendacky@amd.com, konrad.wilk@oracle.com,
mattst88@gmail.com, Janakarajan.Natarajan@amd.com,
dwmw@amazon.co.uk, jpoimboe@redhat.com, marcorr@google.com,
ubizjak@gmail.com, sean.j.christopherson@intel.com,
jmattson@google.com, linux-kernel@vger.kernel.org,
Chao Peng <chao.p.peng@linux.intel.com>
Subject: Re: [PATCH v13 08/12] KVM: x86: Add Intel PT context switch for each vcpu
Date: Tue, 30 Oct 2018 13:26:57 +0200 [thread overview]
Message-ID: <87y3af65fi.fsf@ashishki-desk.ger.corp.intel.com> (raw)
In-Reply-To: <bc192976-2c56-3cfc-a697-cf941a92ad0a@redhat.com>
Paolo Bonzini <pbonzini@redhat.com> writes:
>> If you "have to enable or disable anything" it means you have to
>> override the default. But the default in this patches is "no change
>> compared to before the patches", leaving tracing of both host and guest
>> entirely to the host, so I don't understand your remark. What workflow
>> is broken?
>>
>>> There already are controls in perf that enable/disable guest tracing.
>>
>> You are confusing "tracing guest from the host" and "the guest can trace
>> itself". This patchset is adding support for the latter, and that
I'm not confusing anything. In the terminology that you're using, the
latter breaks the former. This cannot happen.
>> affects directly whether the tracing CPUID leaf can be added to the
>> guest. Therefore it's not perf that can decide whether to turn it on;
>> KVM must know it when /dev/kvm is opened, which is why it is a module
>> parameter.
There is a control in the perf event attribute that enables tracing the
guest. If this control is enabled, the kvm needs to stay away from any
PT related MSRs. Conversely, if kvm is using PT (or, as you say, "the
guest is tracing itself"), the host should not be allowed to ask for
tracing the guest at the same time.
Regards,
--
Alex
next prev parent reply other threads:[~2018-10-30 11:27 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-24 8:05 [PATCH v13 00/12] Intel Processor Trace virtualization enabling Luwei Kang
2018-10-24 8:05 ` [PATCH v13 01/12] perf/x86/intel/pt: Move Intel PT MSRs bit defines to global header Luwei Kang
2018-10-24 8:05 ` [PATCH v13 02/12] perf/x86/intel/pt: Export pt_cap_get() Luwei Kang
2018-10-24 8:05 ` [PATCH v13 03/12] perf/x86/intel/pt: Introduce intel_pt_validate_cap() Luwei Kang
2018-10-24 8:05 ` [PATCH v13 04/12] perf/x86/intel/pt: Add new bit definitions for PT MSRs Luwei Kang
2018-10-24 8:05 ` [PATCH v13 05/12] perf/x86/intel/pt: add new capability for Intel PT Luwei Kang
2018-10-30 9:57 ` Thomas Gleixner
2018-10-24 8:05 ` [PATCH v13 06/12] KVM: x86: Add Intel PT virtualization work mode Luwei Kang
2018-10-24 16:18 ` Jim Mattson
2018-10-25 0:35 ` Kang, Luwei
2018-10-30 9:30 ` Thomas Gleixner
2018-10-30 9:49 ` Paolo Bonzini
2018-10-30 10:13 ` Kang, Luwei
2018-10-30 10:23 ` Thomas Gleixner
2018-10-31 0:36 ` Kang, Luwei
2018-10-24 8:05 ` [PATCH v13 07/12] KVM: x86: Add Intel Processor Trace cpuid emulation Luwei Kang
2018-10-24 8:05 ` [PATCH v13 08/12] KVM: x86: Add Intel PT context switch for each vcpu Luwei Kang
2018-10-24 10:13 ` Alexander Shishkin
2018-10-25 0:06 ` Kang, Luwei
2018-10-29 17:48 ` Paolo Bonzini
2018-10-30 10:00 ` Thomas Gleixner
2018-10-31 10:43 ` Paolo Bonzini
2018-10-31 11:46 ` Alexander Shishkin
2018-10-30 11:26 ` Alexander Shishkin [this message]
2018-10-31 10:49 ` Paolo Bonzini
2018-10-31 11:38 ` Alexander Shishkin
2018-10-31 12:07 ` Paolo Bonzini
2018-10-31 14:21 ` Alexander Shishkin
2018-10-31 14:43 ` Paolo Bonzini
2018-10-24 8:05 ` [PATCH v13 09/12] KVM: x86: Introduce a function to initialize the PT configuration Luwei Kang
2018-10-24 8:05 ` [PATCH v13 10/12] KVM: x86: Implement Intel PT MSRs read/write emulation Luwei Kang
2018-10-24 8:05 ` [PATCH v13 11/12] KVM: x86: Set intercept for Intel PT MSRs read/write Luwei Kang
2018-10-24 8:05 ` [PATCH v13 12/12] KVM: x86: Disable Intel PT when VMXON in L1 guest Luwei Kang
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