linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Nadav Amit <namit@vmware.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	LKML <linux-kernel@vger.kernel.org>, x86 <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>,
	Thomas Hellstrom <thellstrom@vmware.com>,
	Tony Luck <tony.luck@intel.com>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Jessica Yu <jeyu@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [patch 2/2] x86/kvm/vmx: Prevent split lock detection induced #AC wreckage
Date: Thu, 2 Apr 2020 15:44:00 +0000	[thread overview]
Message-ID: <18758F52-BB97-4F47-9481-F66AF4465A06@vmware.com> (raw)
In-Reply-To: <20200402153035.GA13879@linux.intel.com>

> On Apr 2, 2020, at 8:30 AM, Sean Christopherson <sean.j.christopherson@intel.com> wrote:
> 
> On Thu, Apr 02, 2020 at 02:33:00PM +0200, Thomas Gleixner wrote:
>> Without at least minimal handling for split lock detection induced #AC, VMX
>> will just run into the same problem as the VMWare hypervisor, which was
>> reported by Kenneth.
>> 
>> It will inject the #AC blindly into the guest whether the guest is prepared
>> or not.
>> 
>> Add the minimal required handling for it:
>> 
>>  - Check guest state whether CR0.AM is enabled and EFLAGS.AC is set.  If
>>    so, then the #AC originated from CPL3 and the guest has is prepared to
>>    handle it. In this case it does not matter whether the #AC is due to a
>>    split lock or a regular unaligned check.
>> 
>> - Invoke a minimal split lock detection handler. If the host SLD mode is
>>   sld_warn, then handle it in the same way as user space handling works:
>>   Emit a warning, disable SLD and mark the current task with TIF_SLD.
>>   With that resume the guest without injecting #AC.
>> 
>>   If the host mode is sld_fatal or sld_off, emit a warning and deliver
>>   the exception to user space which can crash and burn itself.
>> 
>> Mark the module with MOD_INFO(sld_safe, "Y") so the module loader does not
>> force SLD off.
> 
> Some comments below.  But, any objection to taking Xiaoyao's patches that
> do effectively the same things, minus the MOD_INFO()?  I'll repost them in
> reply to this thread.

IIUC they also deal with emulated split-lock accesses in the host, during
instruction emulation [1]. This seems also to be required, although I am not
sure the approach that he took once emulation encounters a split-lock is
robust.

[1] https://lore.kernel.org/lkml/20200324151859.31068-5-xiaoyao.li@intel.com/

  reply	other threads:[~2020-04-02 15:44 UTC|newest]

Thread overview: 76+ 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
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 [this message]
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=18758F52-BB97-4F47-9481-F66AF4465A06@vmware.com \
    --to=namit@vmware.com \
    --cc=fenghua.yu@intel.com \
    --cc=jeyu@kernel.org \
    --cc=kenny@panix.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=pbonzini@redhat.com \
    --cc=peterz@infradead.org \
    --cc=rostedt@goodmis.org \
    --cc=sean.j.christopherson@intel.com \
    --cc=tglx@linutronix.de \
    --cc=thellstrom@vmware.com \
    --cc=tony.luck@intel.com \
    --cc=x86@kernel.org \
    --cc=xiaoyao.li@intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).