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From: Thomas Gleixner <tglx@linutronix.de>
To: David Laight <David.Laight@ACULAB.COM>
Cc: 'Paolo Bonzini' <pbonzini@redhat.com>,
	Xiaoyao Li <xiaoyao.li@intel.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Fenghua Yu <fenghua.yu@intel.com>, Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>, H Peter Anvin <hpa@zytor.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Dave Hansen <dave.hansen@intel.com>,
	Radim Krcmar <rkrcmar@redhat.com>,
	Ashok Raj <ashok.raj@intel.com>, Tony Luck <tony.luck@intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>,
	Ravi V Shankar <ravi.v.shankar@intel.com>,
	linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: RE: [PATCH v9 09/17] x86/split_lock: Handle #AC exception for split lock
Date: Wed, 16 Oct 2019 17:03:17 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1910161651290.2046@nanos.tec.linutronix.de> (raw)
In-Reply-To: <053924e2d08b4744b9fd10337e83ab2d@AcuMS.aculab.com>

On Wed, 16 Oct 2019, David Laight wrote:

> For the smt case, can you make #AC enable a property of the process?
> Then disable it on the core if either smt process requires it be disabled?

That would be feasible if the logic of the TEST_CTRL_MSR would be AND, but
it's OR.

Thread0	#AC-EN	Thread1 #AC-EN	#AC enabled on core
	0		0		0
	1		0		1
	0		1		1
	1		1		1

So in order to do flips on VMENTER you'd need to IPI the other thread and
handle all the interesting corner cases.

The 'Rescue SMT' mitigation stuff on top of core scheduling is ugly enough
already, but there the state can be transitionally 'unmitigated' while with
#AC you run into trouble immediately if the transitional state is ON at the
wrong point.

Thanks,

	tglx

  reply	other threads:[~2019-10-16 15:03 UTC|newest]

Thread overview: 85+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-18 22:41 [PATCH v9 00/17] x86/split_lock: Enable split lock detection Fenghua Yu
2019-06-18 22:41 ` [PATCH v9 01/17] x86/common: Align cpu_caps_cleared and cpu_caps_set to unsigned long Fenghua Yu
2019-06-18 22:41 ` [PATCH v9 02/17] drivers/net/b44: Align pwol_mask to unsigned long for better performance Fenghua Yu
2019-06-24 15:12   ` David Laight
2019-06-24 18:43     ` Paolo Bonzini
2019-06-18 22:41 ` [PATCH v9 03/17] x86/split_lock: Align x86_capability to unsigned long to avoid split locked access Fenghua Yu
2019-06-24 15:12   ` David Laight
2019-06-25 23:54     ` Fenghua Yu
2019-06-26 19:15       ` Thomas Gleixner
2019-06-18 22:41 ` [PATCH v9 04/17] x86/msr-index: Define MSR_IA32_CORE_CAP and split lock detection bit Fenghua Yu
2019-06-18 22:41 ` [PATCH v9 05/17] x86/cpufeatures: Enumerate MSR_IA32_CORE_CAP Fenghua Yu
2019-06-18 22:41 ` [PATCH v9 06/17] x86/split_lock: Enumerate split lock detection by MSR_IA32_CORE_CAP Fenghua Yu
2019-06-18 22:41 ` [PATCH v9 07/17] x86/split_lock: Enumerate split lock detection on Icelake mobile processor Fenghua Yu
2019-06-18 22:41 ` [PATCH v9 08/17] x86/split_lock: Define MSR TEST_CTL register Fenghua Yu
2019-06-18 22:41 ` [PATCH v9 09/17] x86/split_lock: Handle #AC exception for split lock Fenghua Yu
2019-06-26 20:20   ` Thomas Gleixner
2019-06-26 20:36     ` Fenghua Yu
2019-06-26 21:47       ` Thomas Gleixner
2019-09-25 18:09         ` Sean Christopherson
2019-10-16  6:58           ` Xiaoyao Li
2019-10-16  9:29           ` Thomas Gleixner
2019-10-16 15:59             ` Sean Christopherson
2019-10-16  9:40           ` Paolo Bonzini
2019-10-16  9:47             ` Thomas Gleixner
2019-10-16 10:16               ` Paolo Bonzini
2019-10-16 11:23                 ` Xiaoyao Li
2019-10-16 11:26                   ` Paolo Bonzini
2019-10-16 13:13                     ` Xiaoyao Li
2019-10-16 14:43                       ` Thomas Gleixner
2019-10-16 15:37                         ` Paolo Bonzini
2019-10-16 16:25                           ` Xiaoyao Li
2019-10-16 16:38                             ` Paolo Bonzini
2019-10-17 12:29                           ` [RFD] x86/split_lock: Request to Intel Thomas Gleixner
2019-10-17 17:23                             ` Sean Christopherson
2019-10-17 21:31                               ` Thomas Gleixner
2019-10-17 23:38                                 ` Sean Christopherson
2019-10-17 23:28                             ` Luck, Tony
2019-10-18 10:45                               ` David Laight
2019-10-18 21:03                                 ` hpa
2019-10-18  2:36                             ` Xiaoyao Li
2019-10-18  9:02                               ` Thomas Gleixner
2019-10-18 10:20                                 ` Xiaoyao Li
2019-10-18 10:43                                   ` Peter Zijlstra
2019-10-16 11:49                 ` [PATCH v9 09/17] x86/split_lock: Handle #AC exception for split lock Thomas Gleixner
2019-10-16 11:58                   ` Paolo Bonzini
2019-10-16 13:51                     ` Xiaoyao Li
2019-10-16 14:08                       ` Paolo Bonzini
2019-10-16 14:14                         ` David Laight
2019-10-16 15:03                           ` Thomas Gleixner [this message]
2019-10-16 15:41                         ` Sean Christopherson
2019-10-16 15:43                           ` Paolo Bonzini
2019-10-16 16:23                             ` Sean Christopherson
2019-10-16 17:42                               ` Sean Christopherson
2019-10-17  1:23                                 ` Xiaoyao Li
2019-10-21 13:06                                   ` Paolo Bonzini
2019-10-21 13:03                                 ` Paolo Bonzini
2019-10-21 13:02                               ` Paolo Bonzini
2019-10-16 14:50                       ` Thomas Gleixner
2019-06-18 22:41 ` [PATCH v9 10/17] kvm/x86: Emulate MSR IA32_CORE_CAPABILITY Fenghua Yu
2019-06-18 22:41 ` [PATCH v9 11/17] kvm/vmx: Emulate MSR TEST_CTL Fenghua Yu
2019-06-27  2:24   ` Xiaoyao Li
2019-06-27  7:12     ` Thomas Gleixner
2019-06-27  7:58       ` Xiaoyao Li
2019-06-27 12:11         ` Thomas Gleixner
2019-06-27 12:22           ` Xiaoyao Li
2019-06-18 22:41 ` [PATCH v9 12/17] x86/split_lock: Enable split lock detection by default Fenghua Yu
2019-06-18 22:41 ` [PATCH v9 13/17] x86/split_lock: Disable split lock detection by kernel parameter "nosplit_lock_detect" Fenghua Yu
2019-06-26 20:34   ` Thomas Gleixner
2019-06-26 20:37     ` Fenghua Yu
2019-06-18 22:41 ` [PATCH v9 14/17] x86/split_lock: Add a debugfs interface to enable/disable split lock detection during run time Fenghua Yu
2019-06-26 21:37   ` Thomas Gleixner
2019-06-18 22:41 ` [PATCH v9 15/17] x86/split_lock: Add documentation for split lock detection interface Fenghua Yu
2019-06-26 21:51   ` Thomas Gleixner
2019-06-18 22:41 ` [PATCH v9 16/17] x86/split_lock: Reorganize few header files in order to call WARN_ON_ONCE() in atomic bit ops Fenghua Yu
2019-06-18 22:41 ` [PATCH v9 17/17] x86/split_lock: Warn on unaligned address in atomic bit operations Fenghua Yu
2019-06-26 22:00   ` Thomas Gleixner
2019-09-16 22:39 ` [PATCH 0/3] Fix some 4-byte vs. 8-byte alignment issues Tony Luck
2019-09-16 22:39   ` [PATCH 1/3] x86/common: Align cpu_caps_cleared and cpu_caps_set to unsigned long Tony Luck
2019-11-15 19:26     ` [tip: x86/cpu] x86/cpu: " tip-bot2 for Fenghua Yu
2019-09-16 22:39   ` [PATCH 2/3] drivers/net/b44: Align pwol_mask to unsigned long for better performance Tony Luck
2019-09-16 22:39   ` [PATCH 3/3] x86/split_lock: Align the x86_capability array to size of unsigned long Tony Luck
2019-09-17  8:29     ` David Laight
2019-09-17 19:14       ` Luck, Tony
2019-09-18  8:54         ` David Laight
2019-11-15 19:26     ` [tip: x86/cpu] x86/cpu: " tip-bot2 for Fenghua Yu

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