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From: Thomas Gleixner <tglx@linutronix.de>
To: Paolo Bonzini <pbonzini@redhat.com>,
	Xiaoyao Li <xiaoyao.li@intel.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Andy Lutomirski <luto@amacapital.net>
Cc: x86@kernel.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	David Laight <David.Laight@aculab.com>
Subject: Re: [PATCH v2 3/6] kvm: x86: Emulate split-lock access as a write
Date: Tue, 11 Feb 2020 14:22:16 +0100	[thread overview]
Message-ID: <878sl945tj.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <95d29a81-62d5-f5b6-0eb6-9d002c0bba23@redhat.com>

Paolo Bonzini <pbonzini@redhat.com> writes:
> On 03/02/20 16:16, Xiaoyao Li wrote:
>> A sane guest should never tigger emulation on a split-lock access, but
>> it cannot prevent malicous guest from doing this. So just emulating the
>> access as a write if it's a split-lock access to avoid malicous guest
>> polluting the kernel log.
>
> Saying that anything doing a split lock access is malicious makes little
> sense.

Correct, but we also have to accept, that split lock access can be used
in a malicious way, aka. DoS.

> Split lock detection is essentially a debugging feature, there's a
> reason why the MSR is called "TEST_CTL".  So you don't want to make the

The fact that it ended up in MSR_TEST_CTL does not say anything. That's
where they it ended up to be as it was hastily cobbled together for
whatever reason.

Thanks,

        tglx

  reply	other threads:[~2020-02-11 13:22 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-03 15:16 [PATCH v2 0/6] kvm/split_lock: Add feature split lock detection support in kvm Xiaoyao Li
2020-02-03 15:16 ` [PATCH v2 1/6] x86/split_lock: Add and export get_split_lock_detect_state() Xiaoyao Li
2020-02-03 21:45   ` Sean Christopherson
2020-02-03 15:16 ` [PATCH v2 2/6] x86/split_lock: Add and export split_lock_detect_set() Xiaoyao Li
2020-02-03 15:16 ` [PATCH v2 3/6] kvm: x86: Emulate split-lock access as a write Xiaoyao Li
2020-02-03 20:54   ` Sean Christopherson
2020-02-04  2:55     ` Xiaoyao Li
2020-02-11 12:20   ` Paolo Bonzini
2020-02-11 13:22     ` Thomas Gleixner [this message]
2020-02-11 13:34       ` Paolo Bonzini
2020-02-11 14:02         ` Xiaoyao Li
2020-02-11 14:34           ` David Laight
2020-02-27  0:11         ` Sean Christopherson
2020-03-12 11:42           ` Xiaoyao Li
2020-03-12 15:00             ` Paolo Bonzini
2020-02-03 15:16 ` [PATCH v2 4/6] kvm: vmx: Extend VMX's #AC handding for split lock in guest Xiaoyao Li
2020-02-03 21:14   ` Sean Christopherson
2020-02-04  6:46     ` Xiaoyao Li
2020-02-10 21:30       ` Sean Christopherson
2020-02-03 15:16 ` [PATCH v2 5/6] kvm: x86: Emulate MSR IA32_CORE_CAPABILITIES Xiaoyao Li
2020-02-03 21:43   ` Sean Christopherson
2020-02-04  9:19     ` Xiaoyao Li
2020-02-04  9:37       ` Peter Zijlstra
2020-02-11  3:52         ` Andy Lutomirski
2020-02-11 12:38           ` Peter Zijlstra
2020-02-03 15:16 ` [PATCH v2 6/6] x86: vmx: virtualize split lock detection Xiaoyao Li
2020-02-03 15:58   ` Xiaoyao Li
2020-02-03 18:52   ` Andy Lutomirski
2020-02-03 21:42   ` Sean Christopherson
2020-02-04  2:52     ` Xiaoyao Li
2020-02-04  5:35       ` Sean Christopherson

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