From: Thomas Gleixner <tglx@linutronix.de>
To: Xiaoyao Li <xiaoyao.li@intel.com>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
hpa@zytor.com, Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
kvm@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org
Cc: Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Arvind Sankar <nivedita@alum.mit.edu>,
Fenghua Yu <fenghua.yu@intel.com>,
Tony Luck <tony.luck@intel.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Jim Mattson <jmattson@google.com>
Subject: Re: [PATCH v5 1/9] x86/split_lock: Rework the initialization flow of split lock detection
Date: Tue, 24 Mar 2020 14:31:28 +0100 [thread overview]
Message-ID: <87imitev67.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <95093fb0-df88-0543-c7eb-32b94ac4f99e@intel.com>
Xiaoyao Li <xiaoyao.li@intel.com> writes:
> On 3/24/2020 1:02 AM, Thomas Gleixner wrote:
>> Xiaoyao Li <xiaoyao.li@intel.com> writes:
>>
>>> Current initialization flow of split lock detection has following issues:
>>> 1. It assumes the initial value of MSR_TEST_CTRL.SPLIT_LOCK_DETECT to be
>>> zero. However, it's possible that BIOS/firmware has set it.
>>
>> Ok.
>>
>>> 2. X86_FEATURE_SPLIT_LOCK_DETECT flag is unconditionally set even if
>>> there is a virtualization flaw that FMS indicates the existence while
>>> it's actually not supported.
>>>
>>> 3. Because of #2, KVM cannot rely on X86_FEATURE_SPLIT_LOCK_DETECT flag
>>> to check verify if feature does exist, so cannot expose it to
>>> guest.
>>
>> Sorry this does not make anny sense. KVM is the hypervisor, so it better
>> can rely on the detect flag. Unless you talk about nested virt and a
>> broken L1 hypervisor.
>>
>
> Yeah. It is for the nested virt on a broken L1 hypervisor.
Then please spell it out in the changelog. Changelogs which need crystalballs
to decode are pretty useless.
Thanks,
tglx
next prev parent reply other threads:[~2020-03-24 13:31 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-15 5:05 [PATCH v5 0/9] x86/split_lock: Add feature split lock detection Xiaoyao Li
2020-03-15 5:05 ` [PATCH v5 1/9] x86/split_lock: Rework the initialization flow of " Xiaoyao Li
2020-03-21 0:41 ` Luck, Tony
2020-03-23 17:02 ` Thomas Gleixner
2020-03-23 20:24 ` Thomas Gleixner
2020-03-24 1:10 ` Xiaoyao Li
2020-03-24 10:29 ` Thomas Gleixner
2020-03-25 0:18 ` Xiaoyao Li
2020-03-25 0:52 ` Thomas Gleixner
2020-03-24 11:51 ` Xiaoyao Li
2020-03-24 13:31 ` Thomas Gleixner [this message]
2020-03-15 5:05 ` [PATCH v5 2/9] x86/split_lock: Avoid runtime reads of the TEST_CTRL MSR Xiaoyao Li
2020-03-21 0:43 ` Luck, Tony
2020-03-23 17:06 ` Thomas Gleixner
2020-03-23 17:06 ` Thomas Gleixner
2020-03-24 1:16 ` Xiaoyao Li
2020-03-15 5:05 ` [PATCH v5 3/9] x86/split_lock: Re-define the kernel param option for split_lock_detect Xiaoyao Li
2020-03-21 0:46 ` Luck, Tony
2020-03-23 17:10 ` Thomas Gleixner
2020-03-24 1:38 ` Xiaoyao Li
2020-03-24 10:40 ` Thomas Gleixner
2020-03-24 18:02 ` Sean Christopherson
2020-03-24 18:42 ` Thomas Gleixner
2020-03-25 0:43 ` Xiaoyao Li
2020-03-25 1:03 ` Thomas Gleixner
2020-03-15 5:05 ` [PATCH v5 4/9] x86/split_lock: Export handle_user_split_lock() Xiaoyao Li
2020-03-21 0:48 ` Luck, Tony
2020-03-15 5:05 ` [PATCH v5 5/9] kvm: x86: Emulate split-lock access as a write Xiaoyao Li
2020-03-15 5:05 ` [PATCH v5 6/9] kvm: vmx: Extend VMX's #AC interceptor to handle split lock #AC happens in guest Xiaoyao Li
2020-03-15 5:05 ` [PATCH v5 7/9] kvm: x86: Emulate MSR IA32_CORE_CAPABILITIES Xiaoyao Li
2020-03-15 5:05 ` [PATCH v5 8/9] kvm: vmx: Enable MSR_TEST_CTRL for intel guest Xiaoyao Li
2020-03-15 5:05 ` [PATCH v5 9/9] x86: vmx: virtualize split lock detection Xiaoyao Li
2020-03-23 2:18 ` [PATCH v5 0/9] x86/split_lock: Add feature " Xiaoyao Li
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