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From: Kyle Huey <me@kylehuey.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "Robert O'Callahan" <robert@ocallahan.org>,
	"Andy Lutomirski" <luto@kernel.org>,
	"Ingo Molnar" <mingo@redhat.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
	<x86@kernel.org>, "Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	"Jeff Dike" <jdike@addtoit.com>,
	"Richard Weinberger" <richard@nod.at>,
	"Alexander Viro" <viro@zeniv.linux.org.uk>,
	"Shuah Khan" <shuah@kernel.org>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Borislav Petkov" <bp@suse.de>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
	"Len Brown" <len.brown@intel.com>,
	"Dmitry Safonov" <dsafonov@virtuozzo.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
	"David Matlack" <dmatlack@google.com>,
	"Nadav Amit" <nadav.amit@gmail.com>,
	"Andi Kleen" <andi@firstfloor.org>,
	"open list" <linux-kernel@vger.kernel.org>,
	"open list:USER-MODE LINUX (UML)"
	<user-mode-linux-devel@lists.sourceforge.net>,
	"open list:USER-MODE LINUX (UML)"
	<user-mode-linux-user@lists.sourceforge.net>,
	"open list:KERNEL SELFTEST FRAMEWORK"
	<linux-kselftest@vger.kernel.org>,
	"kvm list" <kvm@vger.kernel.org>
Subject: Re: [PATCH v15 6/9] x86/arch_prctl: Add ARCH_[GET|SET]_CPUID
Date: Mon, 20 Mar 2017 01:01:54 -0700	[thread overview]
Message-ID: <CAP045AoSC_KXrGyscnZiqnvtdr_e6PmmZ4RiD4CEgc_5RiHbhw@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1703142112200.3770@nanos>

On Tue, Mar 14, 2017 at 1:36 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Sat, 11 Mar 2017, Kyle Huey wrote:
>>  static void init_intel_misc_features(struct cpuinfo_x86 *c)
>>  {
>>       u64 msr;
>>
>> +     if (rdmsrl_safe(MSR_MISC_FEATURES_ENABLES, &msr))
>> +             return;
>> +
>> +     msr = 0;
>> +     wrmsrl(MSR_MISC_FEATURES_ENABLES, msr);
>> +     this_cpu_write(msr_misc_features_shadow, msr);
>> +
>>       if (!rdmsrl_safe(MSR_PLATFORM_INFO, &msr)) {
>>               if (msr & MSR_PLATFORM_INFO_CPUID_FAULT)
>>                       set_cpu_cap(c, X86_FEATURE_CPUID_FAULT);
>>       }
>>
>>       probe_xeon_phi_r3mwait(c);
>
> The way you are doing it breaks the ring3 mwait feature because you
> overwrite the R3MWAIT bit the first time you update the MSR on context
> switch.

Indeed.  Good catch.

- Kyle

WARNING: multiple messages have this Message-ID (diff)
From: Kyle Huey <me@kylehuey.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "Robert O'Callahan" <robert@ocallahan.org>,
	"Andy Lutomirski" <luto@kernel.org>,
	"Ingo Molnar" <mingo@redhat.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
	<x86@kernel.org>, "Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	"Jeff Dike" <jdike@addtoit.com>,
	"Richard Weinberger" <richard@nod.at>,
	"Alexander Viro" <viro@zeniv.linux.org.uk>,
	"Shuah Khan" <shuah@kernel.org>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Borislav Petkov" <bp@suse.de>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
	"Len Brown" <len.brown@intel.com>,
	"Dmitry Safonov" <dsafonov@virtuozzo.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Subject: Re: [PATCH v15 6/9] x86/arch_prctl: Add ARCH_[GET|SET]_CPUID
Date: Mon, 20 Mar 2017 01:01:54 -0700	[thread overview]
Message-ID: <CAP045AoSC_KXrGyscnZiqnvtdr_e6PmmZ4RiD4CEgc_5RiHbhw@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1703142112200.3770@nanos>

On Tue, Mar 14, 2017 at 1:36 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Sat, 11 Mar 2017, Kyle Huey wrote:
>>  static void init_intel_misc_features(struct cpuinfo_x86 *c)
>>  {
>>       u64 msr;
>>
>> +     if (rdmsrl_safe(MSR_MISC_FEATURES_ENABLES, &msr))
>> +             return;
>> +
>> +     msr = 0;
>> +     wrmsrl(MSR_MISC_FEATURES_ENABLES, msr);
>> +     this_cpu_write(msr_misc_features_shadow, msr);
>> +
>>       if (!rdmsrl_safe(MSR_PLATFORM_INFO, &msr)) {
>>               if (msr & MSR_PLATFORM_INFO_CPUID_FAULT)
>>                       set_cpu_cap(c, X86_FEATURE_CPUID_FAULT);
>>       }
>>
>>       probe_xeon_phi_r3mwait(c);
>
> The way you are doing it breaks the ring3 mwait feature because you
> overwrite the R3MWAIT bit the first time you update the MSR on context
> switch.

Indeed.  Good catch.

- Kyle

  reply	other threads:[~2017-03-20  8:02 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-11 19:46 [PATCH v15 0/9] x86/arch_prctl Add ARCH_[GET|SET]_CPUID for controlling the CPUID instruction Kyle Huey
2017-03-11 19:46 ` Kyle Huey
2017-03-11 19:46 ` [PATCH v15 1/9] x86/arch_prctl/64: Use SYSCALL_DEFINE2 to define sys_arch_prctl Kyle Huey
2017-03-11 19:46   ` Kyle Huey
2017-03-11 19:46 ` [PATCH v15 2/9] x86/arch_prctl/64: Rename do_arch_prctl to do_arch_prctl_64 Kyle Huey
2017-03-11 19:46   ` Kyle Huey
2017-03-11 19:46 ` [PATCH v15 3/9] x86/arch_prctl: Add do_arch_prctl_common Kyle Huey
2017-03-11 19:46   ` Kyle Huey
2017-03-11 19:46 ` [PATCH v15 4/9] x86/syscalls/32: Wire up arch_prctl on x86-32 Kyle Huey
2017-03-11 19:46   ` Kyle Huey
2017-03-11 19:46 ` [PATCH v15 5/9] x86/cpufeature: Detect CPUID faulting support Kyle Huey
2017-03-11 19:46   ` Kyle Huey
2017-03-11 19:46 ` [PATCH v15 6/9] x86/arch_prctl: Add ARCH_[GET|SET]_CPUID Kyle Huey
2017-03-11 19:46   ` Kyle Huey
2017-03-14 20:36   ` Thomas Gleixner
2017-03-14 20:36     ` Thomas Gleixner
2017-03-20  8:01     ` Kyle Huey [this message]
2017-03-20  8:01       ` Kyle Huey
2017-03-14 21:47   ` Linus Torvalds
2017-03-14 21:47     ` Linus Torvalds
2017-03-16 11:09     ` Michael Ellerman
2017-03-16 11:09       ` Michael Ellerman
2017-03-16 14:30       ` Kyle Huey
2017-03-16 14:30         ` Kyle Huey
2017-03-16 18:23         ` Linus Torvalds
2017-03-16 18:23           ` Linus Torvalds
2017-03-17  7:56           ` Geert Uytterhoeven
2017-03-17  7:56             ` Geert Uytterhoeven
2017-03-11 19:47 ` [PATCH v15 7/9] x86/arch_prctl: Selftest for ARCH_[GET|SET]_CPUID Kyle Huey
2017-03-11 19:47   ` Kyle Huey
2017-03-11 19:47 ` [PATCH v15 8/9] KVM: x86: virtualize cpuid faulting Kyle Huey
2017-03-11 19:47   ` Kyle Huey
2017-03-11 19:47 ` [PATCH v15 9/9] x86/arch_prctl: Rename 'code' argument to 'option' Kyle Huey
2017-03-11 19:47   ` Kyle Huey
2017-03-14 20:07   ` Thomas Gleixner
2017-03-14 20:07     ` Thomas Gleixner
2017-03-20  8:01     ` Kyle Huey
2017-03-20  8:01       ` Kyle Huey

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