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From: Ingo Molnar <mingo@kernel.org>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
	Borislav Petkov <bp@alien8.de>,
	hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com,
	akpm@linux-foundation.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, x86@kernel.org, jgross@suse.com,
	konrad.wilk@oracle.com, elliott@hpe.com,
	boris.ostrovsky@oracle.com, Toshi Kani <toshi.kani@hpe.com>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] x86/mm: fix regression with huge pages on PAE
Date: Thu, 12 Nov 2015 09:55:27 +0100	[thread overview]
Message-ID: <20151112085527.GB18963@gmail.com> (raw)
In-Reply-To: <20151112084616.EABFE19B@black.fi.intel.com>


* Kirill A. Shutemov <kirill.shutemov@linux.intel.com> wrote:

> > But, what problems do you expect with having a wider mask than its primary usage? 
> > If it's used for 32-bit values it will be truncated down safely. (But I have not 
> > tested it, so I might be missing some complication.)
> 
> Yeah, I basically worry about non realized side effect.

Such a worry is prudent, the best way would be to double check a disassembly of a 
before/after vmlinux and see in which functions they differ and why.

We might have similar bugs elsewhere - silently fixed by such a change.

Thanks,

	Ingo

WARNING: multiple messages have this Message-ID (diff)
From: Ingo Molnar <mingo@kernel.org>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
	Borislav Petkov <bp@alien8.de>,
	hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com,
	akpm@linux-foundation.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, x86@kernel.org, jgross@suse.com,
	konrad.wilk@oracle.com, elliott@hpe.com,
	boris.ostrovsky@oracle.com, Toshi Kani <toshi.kani@hpe.com>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] x86/mm: fix regression with huge pages on PAE
Date: Thu, 12 Nov 2015 09:55:27 +0100	[thread overview]
Message-ID: <20151112085527.GB18963@gmail.com> (raw)
In-Reply-To: <20151112084616.EABFE19B@black.fi.intel.com>


* Kirill A. Shutemov <kirill.shutemov@linux.intel.com> wrote:

> > But, what problems do you expect with having a wider mask than its primary usage? 
> > If it's used for 32-bit values it will be truncated down safely. (But I have not 
> > tested it, so I might be missing some complication.)
> 
> Yeah, I basically worry about non realized side effect.

Such a worry is prudent, the best way would be to double check a disassembly of a 
before/after vmlinux and see in which functions they differ and why.

We might have similar bugs elsewhere - silently fixed by such a change.

Thanks,

	Ingo

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  parent reply	other threads:[~2015-11-12  8:55 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-09 23:18 [PATCH] x86/mm: fix regression with huge pages on PAE Kirill A. Shutemov
2015-11-09 23:18 ` Kirill A. Shutemov
2015-11-09 23:43 ` Toshi Kani
2015-11-09 23:43   ` Toshi Kani
2015-11-09 23:57   ` Kirill A. Shutemov
2015-11-09 23:57     ` Kirill A. Shutemov
2015-11-10  0:12     ` Toshi Kani
2015-11-10  0:12       ` Toshi Kani
2015-11-10 12:34 ` Borislav Petkov
2015-11-10 12:34   ` Borislav Petkov
2015-11-10 13:53   ` Kirill A. Shutemov
2015-11-10 13:53     ` Kirill A. Shutemov
2015-11-10 14:46     ` Borislav Petkov
2015-11-10 14:46       ` Borislav Petkov
2015-11-10 15:07       ` Kirill A. Shutemov
2015-11-10 15:07         ` Kirill A. Shutemov
2015-11-10 17:04         ` Borislav Petkov
2015-11-10 17:04           ` Borislav Petkov
2015-11-11  9:51           ` Borislav Petkov
2015-11-11  9:51             ` Borislav Petkov
2015-11-12  7:48             ` Ingo Molnar
2015-11-12  7:48               ` Ingo Molnar
2015-11-12  7:57               ` Kirill A. Shutemov
2015-11-12  7:57                 ` Kirill A. Shutemov
2015-11-12  8:00                 ` Ingo Molnar
2015-11-12  8:00                   ` Ingo Molnar
2015-11-12  8:46                   ` Kirill A. Shutemov
2015-11-12  8:46                     ` Kirill A. Shutemov
2015-11-12  8:54                     ` Ingo Molnar
2015-11-12  8:54                       ` Ingo Molnar
2015-11-12  9:00                       ` Kirill A. Shutemov
2015-11-12  9:00                         ` Kirill A. Shutemov
2015-11-12 13:29                         ` Ingo Molnar
2015-11-12 13:29                           ` Ingo Molnar
2015-11-24 14:59                         ` Boris Ostrovsky
2015-11-24 14:59                           ` Boris Ostrovsky
2015-11-24 20:14                           ` Kirill A. Shutemov
2015-11-24 20:14                             ` Kirill A. Shutemov
2015-11-25 10:27                             ` Borislav Petkov
2015-11-25 10:27                               ` Borislav Petkov
2015-11-27 10:14                             ` Ingo Molnar
2015-11-27 10:14                               ` Ingo Molnar
2015-11-12  8:55                     ` Ingo Molnar [this message]
2015-11-12  8:55                       ` Ingo Molnar
2015-11-12 19:29                   ` Linus Torvalds
2015-11-12 19:29                     ` Linus Torvalds
2015-11-13  9:01                     ` Dan Williams
2015-11-13  9:01                       ` Dan Williams
2015-11-30 10:10 [PATCH] tip-queue 2015-11-30 Borislav Petkov
2015-11-30 10:10 ` [PATCH] x86/mm: Fix regression with huge pages on PAE Borislav Petkov

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