From: Andy Lutomirski <luto@amacapital.net>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>,
Jessica Yu <jeyu@kernel.org>,
Rasmus Villemoes <rasmus.villemoes@prevas.dk>,
LKML <linux-kernel@vger.kernel.org>,
x86@kernel.org, "Kenneth R. Crudup" <kenny@panix.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Fenghua Yu <fenghua.yu@intel.com>,
Xiaoyao Li <xiaoyao.li@intel.com>, Nadav Amit <namit@vmware.com>,
Thomas Hellstrom <thellstrom@vmware.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Tony Luck <tony.luck@intel.com>,
Steven Rostedt <rostedt@goodmis.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
jannh@google.com, keescook@chromium.org, vbox-dev@virtualbox.org
Subject: Re: [patch 1/2] x86,module: Detect VMX modules and disable Split-Lock-Detect
Date: Fri, 3 Apr 2020 13:58:17 -0700 [thread overview]
Message-ID: <737F6739-9B8B-4C73-91D3-B873D5780F5E@amacapital.net> (raw)
In-Reply-To: <87o8s8l7t3.fsf@nanos.tec.linutronix.de>
> On Apr 3, 2020, at 11:54 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
>
> Peter Zijlstra <peterz@infradead.org> writes:
>>> On Fri, Apr 03, 2020 at 04:35:00PM +0200, Jessica Yu wrote:
>>> +++ Rasmus Villemoes [03/04/20 01:42 +0200]:
>>>> On 02/04/2020 14.32, Thomas Gleixner wrote:
>>>>> From: Peter Zijlstra <peterz@infradead.org>
>>>>>
>>>>> It turns out that with Split-Lock-Detect enabled (default) any VMX
>>>>> hypervisor needs at least a little modification in order to not blindly
>>>>> inject the #AC into the guest without the guest being ready for it.
>>>>>
>>>>> Since there is no telling which module implements a hypervisor, scan the
>>>>> module text and look for the VMLAUNCH instruction. If found, the module is
>>>>> assumed to be a hypervisor of some sort and SLD is disabled.
>>>>
>>>> How long does that scan take/add to module load time? Would it make
>>>> sense to exempt in-tree modules?
>>>>
>>>> Rasmus
>>>
>>> I second Rasmus's question. It seems rather unfortunate that we have
>>> to do this text scan for every module load on x86, when it doesn't
>>> apply to the majority of them, and only to a handful of out-of-tree
>>> hypervisor modules (assuming kvm is taken care of already).
>>>
>>> I wonder if it would make sense then to limit the text scans to just
>>> out-of-tree modules (i.e., missing the intree modinfo flag)?
>>
>> It would; didn't know there was one.
>
> But that still would not make it complete.
>
> I was staring at virtualbox today after Jann pointed out that this
> sucker does complete backwards things.
>
> The kernel driver does not contain any VM* instructions at all.
>
> The actual hypervisor code is built as a separate binary and somehow
> loaded into the kernel with their own magic fixup of relocations and
> function linking. This "design" probably comes from the original
> virtualbox implementation which circumvented GPL that way.
>
> TBH, I don't care if we wreckage virtualbox simply because that thing is
> already a complete and utter trainwreck violating taste and common sense
> in any possible way. Just for illustration:
>
> - It installs preempt notifiers and the first thing in the callback
> function is to issue 'stac()'!
>
> - There is quite some other horrible code in there which fiddles in
> the guts of the kernel just because it can.
>
> - Conditionals in release code which check stuff like
> VBOX_WITH_TEXT_MODMEM_HACK, VBOX_WITH_EFLAGS_AC_SET_IN_VBOXDRV,
> VBOX_WITH_NON_PROD_HACK_FOR_PERF_STACKS along with the most absurd
> hacks ever.
>
> If you feel the need to look yourself, please use your eyecancer
> protection gear.
>
> Can someone at Oracle please make sure, that this monstrosity gets shred
> in pieces?
>
> Enough vented, but that still does not solve the SLD problem in any
> sensible way.
Could we unexport set_memory_x perhaps? And maybe try to make virtualbox break in as many ways as possible?
>
> Thanks,
>
> tglx
next prev parent reply other threads:[~2020-04-03 20:58 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-02 12:32 [patch 0/2] x86: Prevent Split-Lock-Detection wreckage on VMX hypervisors Thomas Gleixner
2020-04-02 12:32 ` [patch 1/2] x86,module: Detect VMX modules and disable Split-Lock-Detect Thomas Gleixner
2020-04-02 15:23 ` [patch v2 " Peter Zijlstra
2020-04-02 16:20 ` Xiaoyao Li
2020-04-02 16:25 ` Peter Zijlstra
2020-04-02 16:39 ` Nadav Amit
2020-04-02 16:41 ` Xiaoyao Li
2020-04-02 17:34 ` Thomas Gleixner
2020-04-02 17:51 ` Sean Christopherson
2020-04-02 18:51 ` Peter Zijlstra
2020-04-02 20:23 ` Sean Christopherson
2020-04-02 21:04 ` Thomas Gleixner
2020-04-02 21:16 ` Sean Christopherson
2020-04-03 8:09 ` David Laight
2020-04-03 14:33 ` Peter Zijlstra
2020-04-02 23:42 ` [patch " Rasmus Villemoes
2020-04-03 14:35 ` Jessica Yu
2020-04-03 15:21 ` Peter Zijlstra
2020-04-03 16:01 ` Sean Christopherson
2020-04-03 16:12 ` Peter Zijlstra
2020-04-03 16:16 ` David Laight
2020-04-03 16:39 ` Peter Zijlstra
2020-04-03 16:25 ` Sean Christopherson
2020-04-03 16:40 ` Peter Zijlstra
2020-04-03 16:48 ` Nadav Amit
2020-04-03 17:21 ` Sean Christopherson
2020-04-03 18:53 ` Thomas Gleixner
2020-04-03 20:58 ` Andy Lutomirski [this message]
2020-04-03 21:49 ` Thomas Gleixner
2020-04-03 11:29 ` kbuild test robot
2020-04-03 14:43 ` kbuild test robot
2020-04-03 16:36 ` Sean Christopherson
2020-04-03 16:41 ` Peter Zijlstra
2020-04-03 18:35 ` Jessica Yu
2020-04-06 12:23 ` Christoph Hellwig
2020-04-06 14:40 ` Peter Zijlstra
2020-04-06 15:18 ` Christoph Hellwig
2020-04-06 15:22 ` Peter Zijlstra
2020-04-06 18:27 ` Steven Rostedt
2020-04-02 12:33 ` [patch 2/2] x86/kvm/vmx: Prevent split lock detection induced #AC wreckage Thomas Gleixner
2020-04-02 15:30 ` Sean Christopherson
2020-04-02 15:44 ` Nadav Amit
2020-04-02 16:04 ` Sean Christopherson
2020-04-02 16:56 ` Thomas Gleixner
2020-04-02 15:55 ` [PATCH 0/3] x86: KVM: VMX: Add basic split-lock #AC handling Sean Christopherson
2020-04-02 15:55 ` [PATCH 1/3] KVM: x86: Emulate split-lock access as a write in emulator Sean Christopherson
2020-04-02 15:55 ` [PATCH 2/3] x86/split_lock: Refactor and export handle_user_split_lock() for KVM Sean Christopherson
2020-04-02 17:01 ` Thomas Gleixner
2020-04-02 17:19 ` Sean Christopherson
2020-04-02 19:06 ` Thomas Gleixner
2020-04-10 4:39 ` Xiaoyao Li
2020-04-10 10:21 ` Paolo Bonzini
2020-04-02 15:55 ` [PATCH 3/3] KVM: VMX: Extend VMX's #AC interceptor to handle split lock #AC in guest Sean Christopherson
2020-04-02 17:19 ` Thomas Gleixner
2020-04-02 17:40 ` Sean Christopherson
2020-04-02 20:07 ` Thomas Gleixner
2020-04-02 20:36 ` Andy Lutomirski
2020-04-02 20:48 ` Peter Zijlstra
2020-04-02 20:51 ` Sean Christopherson
2020-04-02 22:27 ` Thomas Gleixner
2020-04-02 22:40 ` Nadav Amit
2020-04-02 23:03 ` Thomas Gleixner
2020-04-02 23:08 ` Steven Rostedt
2020-04-02 23:16 ` Kenneth R. Crudup
2020-04-02 23:18 ` Jim Mattson
2020-04-03 12:16 ` Thomas Gleixner
2020-04-10 10:23 ` [PATCH 0/3] x86: KVM: VMX: Add basic split-lock #AC handling Paolo Bonzini
2020-04-10 11:14 ` Thomas Gleixner
2020-04-02 13:43 ` [patch 0/2] x86: Prevent Split-Lock-Detection wreckage on VMX hypervisors Kenneth R. Crudup
2020-04-02 14:32 ` Peter Zijlstra
2020-04-02 14:41 ` Kenneth R. Crudup
2020-04-02 14:46 ` Peter Zijlstra
2020-04-02 14:53 ` Kenneth R. Crudup
2020-04-02 14:37 ` Thomas Gleixner
2020-04-02 14:47 ` Nadav Amit
2020-04-02 15:11 ` Peter Zijlstra
2020-04-02 14:53 [patch 1/2] x86,module: Detect VMX modules and disable Split-Lock-Detect Andy Lutomirski
2020-04-02 15:02 ` Kenneth R. Crudup
2020-04-02 16:46 ` Thomas Gleixner
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