From: David Laight <David.Laight@ACULAB.COM>
To: 'Linus Torvalds' <torvalds@linux-foundation.org>,
Tony Luck <tony.luck@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Peter Anvin <hpa@zytor.com>,
Borislav Petkov <bp@alien8.de>,
linux-edac <linux-edac@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
Dan Williams <dan.j.williams@intel.com>,
Dave Jiang <dave.jiang@intel.com>
Subject: RE: [PATCH] x86/mce: Fix set_mce_nospec() to avoid #GP fault
Date: Mon, 10 Sep 2018 13:52:24 +0000 [thread overview]
Message-ID: <74a1ec83d9f44875b86d84f52d65a32c@AcuMS.aculab.com> (raw)
In-Reply-To: <CA+55aFy+R8pw1aX84cGNBNbtDgOMANXqX3+-MxAbLZRnUj=0vg@mail.gmail.com>
From: Linus Torvalds
> ...
> You could literally do something like
>
> /* Make it canonical in case we flipped the high bit */
> addr = (long)(addr<<1)>>1;
Isn't it safer to use a mask and let the compiler decide if two
shifts are a good implementation?
addr &= ~HIGH_MAGIC_BIT;
ISTR fixing a bug in gld where it had (foo << 16) >> 16 instead
of foo & 0xffff. Didn't work well on 64bit.
(I may need to recompile that old gcc/gld again.
Failed miserably last time I tried.)
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
prev parent reply other threads:[~2018-09-10 13:50 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-30 21:45 Tony Luck
2018-08-31 1:29 ` Linus Torvalds
2018-08-31 1:48 ` Tony Luck
2018-08-31 4:25 ` Linus Torvalds
2018-08-31 15:35 ` Thomas Gleixner
2018-08-31 16:55 ` [PATCH V2] " Luck, Tony
2018-08-31 16:57 ` Linus Torvalds
2018-09-01 13:03 ` [tip:x86/urgent] " tip-bot for LuckTony
2018-09-10 13:52 ` David Laight [this message]
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