From: Andy Lutomirski <luto@amacapital.net>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>,
Xiaoyao Li <xiaoyao.li@intel.com>,
"Luck, Tony" <tony.luck@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
H Peter Anvin <hpa@zytor.com>, "Raj, Ashok" <ashok.raj@intel.com>,
"Shankar, Ravi V" <ravi.v.shankar@intel.com>,
linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>
Subject: Re: [PATCH v10 6/6] x86/split_lock: Enable split lock detection by kernel parameter
Date: Thu, 21 Nov 2019 18:21:20 -0800 [thread overview]
Message-ID: <81CEB9B7-79EA-4B02-A79C-C9113331A28A@amacapital.net> (raw)
In-Reply-To: <20191122015225.GG16617@linux.intel.com>
> On Nov 21, 2019, at 5:52 PM, Sean Christopherson <sean.j.christopherson@intel.com> wrote:
>
> On Thu, Nov 21, 2019 at 03:53:29PM -0800, Fenghua Yu wrote:
>>> On Thu, Nov 21, 2019 at 03:18:46PM -0800, Andy Lutomirski wrote:
>>>
>>>> On Nov 21, 2019, at 2:29 PM, Luck, Tony <tony.luck@intel.com> wrote:
>>>>
>>>>> It would be really, really nice if we could pass this feature through to a VM. Can we?
>>>>
>>>> It's hard because the MSR is core scoped rather than thread scoped. So on an HT
>>>> enabled system a pair of logical processors gets enabled/disabled together.
>>>>
>>>
>>> Well that sucks.
>>>
>>> Could we pass it through if the host has no HT? Debugging is *so* much
>>> easier in a VM. And HT is a bit dubious these days anyway.
>>
>> I think it's doable to pass it through to KVM. The difficulty is to disable
>> split lock detection in KVM because that will disable split lock on the whole
>> core including threads for the host. Without disabling split lock in KVM,
>> it's doable to debug split lock in KVM.
>>
>> Sean and Xiaoyao are working on split lock for KVM (in separate patch set).
>> They may have insight on how to do this.
>
> Yes, with SMT off KVM could allow the guest to enable split lock #AC, but
> for the initial implementation we'd want to allow it if and only if split
> lock #AC is disabled in the host kernel. Otherwise we have to pull in the
> logic to control whether or not a guest can disable split lock #AC, what
> to do if a split lock #AC happens when it's enabled by the host but
> disabled by the guest, etc...
What’s the actual issue? There’s a window around entry and exit when a split lock in the host might not give #AC, but as long as no user code is run, this doesn’t seem like a big problem.
next prev parent reply other threads:[~2019-11-22 2:21 UTC|newest]
Thread overview: 145+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-21 0:53 [PATCH v10 0/6] Enable split lock detection for real time and debug Fenghua Yu
2019-11-21 0:53 ` [PATCH v10 1/6] x86/msr-index: Add two new MSRs Fenghua Yu
2019-11-21 0:53 ` [PATCH v10 2/6] x86/cpufeatures: Enumerate the IA32_CORE_CAPABILITIES MSR Fenghua Yu
2019-11-21 0:53 ` [PATCH v10 3/6] x86/split_lock: Enumerate split lock detection by " Fenghua Yu
2019-11-21 0:53 ` [PATCH v10 4/6] x86/split_lock: Enumerate split lock detection if the IA32_CORE_CAPABILITIES MSR is not supported Fenghua Yu
2019-11-21 22:07 ` Andy Lutomirski
2019-11-22 0:37 ` Fenghua Yu
2019-11-22 2:13 ` Andy Lutomirski
2019-11-22 9:46 ` Peter Zijlstra
2019-11-21 0:53 ` [PATCH v10 5/6] x86/split_lock: Handle #AC exception for split lock Fenghua Yu
2019-11-21 22:10 ` Andy Lutomirski
2019-11-21 23:14 ` Fenghua Yu
2019-11-21 23:12 ` Andy Lutomirski
2019-11-21 0:53 ` [PATCH v10 6/6] x86/split_lock: Enable split lock detection by kernel parameter Fenghua Yu
2019-11-21 6:04 ` Ingo Molnar
2019-11-21 13:01 ` Peter Zijlstra
2019-11-21 13:15 ` Peter Zijlstra
2019-11-21 21:51 ` Luck, Tony
2019-11-21 22:24 ` Andy Lutomirski
2019-11-21 22:29 ` Luck, Tony
2019-11-21 23:18 ` Andy Lutomirski
2019-11-21 23:53 ` Fenghua Yu
2019-11-22 1:52 ` Sean Christopherson
2019-11-22 2:21 ` Andy Lutomirski [this message]
2019-11-22 2:39 ` Xiaoyao Li
2019-11-22 2:57 ` Andy Lutomirski
2019-11-21 23:55 ` Luck, Tony
2019-11-22 0:55 ` Luck, Tony
2019-11-22 10:08 ` Peter Zijlstra
2019-11-21 16:14 ` Fenghua Yu
2019-11-21 17:14 ` Ingo Molnar
2019-11-21 17:35 ` Peter Zijlstra
2019-11-21 17:12 ` Ingo Molnar
2019-11-21 17:34 ` Luck, Tony
2019-11-22 10:51 ` Peter Zijlstra
2019-11-22 15:27 ` Peter Zijlstra
2019-11-22 17:22 ` Luck, Tony
2019-11-22 20:23 ` Peter Zijlstra
2019-11-22 18:02 ` Luck, Tony
2019-11-22 20:23 ` Peter Zijlstra
2019-11-22 20:42 ` Fenghua Yu
2019-11-22 21:25 ` Andy Lutomirski
2019-12-12 8:57 ` Peter Zijlstra
2019-12-12 18:52 ` Luck, Tony
2019-12-12 19:46 ` Luck, Tony
2019-12-12 20:01 ` Andy Lutomirski
2019-12-16 16:21 ` David Laight
2019-11-22 18:44 ` Sean Christopherson
2019-11-22 20:30 ` Peter Zijlstra
2019-11-23 0:30 ` Luck, Tony
2019-11-25 16:13 ` Sean Christopherson
2019-12-02 18:20 ` Luck, Tony
2019-12-12 8:59 ` Peter Zijlstra
2020-01-10 19:24 ` [PATCH v11] x86/split_lock: Enable split lock detection by kernel Luck, Tony
2020-01-14 5:55 ` Sean Christopherson
2020-01-15 22:27 ` Luck, Tony
2020-01-15 22:57 ` Sean Christopherson
2020-01-15 23:48 ` Luck, Tony
2020-01-22 18:55 ` [PATCH v12] " Luck, Tony
2020-01-22 19:04 ` Borislav Petkov
2020-01-22 20:03 ` Luck, Tony
2020-01-22 20:55 ` Borislav Petkov
2020-01-22 22:42 ` Arvind Sankar
2020-01-22 22:52 ` Arvind Sankar
2020-01-22 23:24 ` Luck, Tony
2020-01-23 0:45 ` Arvind Sankar
2020-01-23 1:23 ` Luck, Tony
2020-01-23 4:21 ` Arvind Sankar
2020-01-23 17:15 ` Luck, Tony
2020-01-23 3:53 ` [PATCH v13] " Luck, Tony
2020-01-23 4:45 ` Arvind Sankar
2020-01-23 23:16 ` [PATCH v14] " Luck, Tony
2020-01-24 21:36 ` Thomas Gleixner
2020-01-25 2:47 ` [PATCH v15] " Luck, Tony
2020-01-25 10:44 ` Borislav Petkov
2020-01-25 19:55 ` Luck, Tony
2020-01-25 20:12 ` Peter Zijlstra
2020-01-25 20:33 ` Borislav Petkov
2020-01-25 21:42 ` Luck, Tony
2020-01-25 22:17 ` Borislav Petkov
2020-01-25 20:29 ` Borislav Petkov
2020-01-25 13:41 ` Thomas Gleixner
2020-01-25 22:07 ` [PATCH v16] " Luck, Tony
2020-01-25 22:43 ` Mark D Rustad
2020-01-25 23:10 ` Luck, Tony
2020-01-26 17:27 ` Mark D Rustad
2020-01-26 20:05 ` [PATCH v17] " Luck, Tony
2020-01-29 12:31 ` Thomas Gleixner
2020-01-29 15:24 ` [tip: x86/cpu] " tip-bot2 for Peter Zijlstra (Intel)
2020-02-03 20:41 ` [PATCH v17] " Sean Christopherson
2020-02-06 0:49 ` [PATCH] x86/split_lock: Avoid runtime reads of the TEST_CTRL MSR Luck, Tony
2020-02-06 1:18 ` Andy Lutomirski
2020-02-06 16:46 ` Luck, Tony
2020-02-06 19:37 ` Andy Lutomirski
2020-03-03 19:22 ` Sean Christopherson
2020-02-04 0:04 ` [PATCH v17] x86/split_lock: Enable split lock detection by kernel Sean Christopherson
2020-02-04 12:52 ` Thomas Gleixner
2020-01-26 0:34 ` [PATCH v16] " Andy Lutomirski
2020-01-26 20:01 ` Luck, Tony
2020-01-25 21:25 ` [PATCH v15] " Arvind Sankar
2020-01-25 21:50 ` Luck, Tony
2020-01-25 23:51 ` Arvind Sankar
2020-01-26 2:52 ` Luck, Tony
2020-01-27 2:05 ` Tony Luck
2020-01-27 8:04 ` Peter Zijlstra
2020-01-27 8:36 ` Peter Zijlstra
2020-01-27 17:35 ` Luck, Tony
2020-01-27 8:02 ` Peter Zijlstra
2019-12-13 0:09 ` [PATCH v11] x86/split_lock: Enable split lock detection by kernel parameter Tony Luck
2019-12-13 0:16 ` Luck, Tony
2019-11-21 17:43 ` [PATCH v10 6/6] " David Laight
2019-11-21 17:51 ` Andy Lutomirski
2019-11-21 18:53 ` Fenghua Yu
2019-11-21 19:01 ` Andy Lutomirski
2019-11-21 20:25 ` Fenghua Yu
2019-11-21 20:19 ` Peter Zijlstra
2019-11-21 19:46 ` Peter Zijlstra
2019-11-21 20:25 ` Peter Zijlstra
2019-11-21 21:22 ` Andy Lutomirski
2019-11-22 9:25 ` Peter Zijlstra
2019-11-22 17:48 ` Luck, Tony
2019-11-22 20:31 ` Peter Zijlstra
2019-11-22 21:23 ` Andy Lutomirski
2019-12-11 17:52 ` Peter Zijlstra
2019-12-11 18:12 ` Andy Lutomirski
2019-12-11 22:34 ` Peter Zijlstra
2019-12-12 19:40 ` Andy Lutomirski
2019-12-16 9:59 ` David Laight
2019-12-16 17:22 ` Andy Lutomirski
2019-12-16 17:45 ` David Laight
2019-12-16 18:06 ` Andy Lutomirski
2019-12-17 10:03 ` David Laight
2019-12-11 18:44 ` Luck, Tony
2019-12-11 22:39 ` Peter Zijlstra
2019-12-12 10:36 ` David Laight
2019-12-12 13:04 ` Peter Zijlstra
2019-12-12 16:02 ` Andy Lutomirski
2019-12-12 16:23 ` David Laight
2019-12-12 16:29 ` David Laight
2019-11-21 19:56 ` Peter Zijlstra
2019-11-21 21:01 ` Andy Lutomirski
2019-11-22 9:36 ` Peter Zijlstra
2019-11-22 9:46 ` David Laight
2019-11-22 20:32 ` Peter Zijlstra
2019-11-21 8:00 ` 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=81CEB9B7-79EA-4B02-A79C-C9113331A28A@amacapital.net \
--to=luto@amacapital.net \
--cc=ashok.raj@intel.com \
--cc=bp@alien8.de \
--cc=fenghua.yu@intel.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=ravi.v.shankar@intel.com \
--cc=sean.j.christopherson@intel.com \
--cc=tglx@linutronix.de \
--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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.