From: Linus Torvalds <torvalds@linux-foundation.org>
To: 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: Thu, 30 Aug 2018 21:25:03 -0700 [thread overview]
Message-ID: <CA+55aFy+R8pw1aX84cGNBNbtDgOMANXqX3+-MxAbLZRnUj=0vg@mail.gmail.com> (raw)
In-Reply-To: <CA+8MBbLKWj0RVM5astYB7_htJZ0203cQ65BWJO_o4=WDWn2kAw@mail.gmail.com>
On Thu, Aug 30, 2018 at 6:49 PM Tony Luck <tony.luck@intel.com> wrote:
>
> Just checking "do we have a non-canonical address" at the bottom of that
> call stack and flipping bit 63 back on again seems like a bad idea.
You could literally do something like
/* Make it canonical in case we flipped the high bit */
addr = (long)(addr<<1)>>1;
in the call to clflush and it magically does the right thing.
Pretty? No. But with a big comment about what is going on and why it's
done, I think it's prettier than your much bigger patch.
I dunno. It does strike me as a bit hacky, but I'd rather have a
*small* one-liner hack that generates two instructions, than add a
complex hack that modifies the page tables three times and has a
serializing instruction in it.
Both are subtle fixes for a subtle issue, but one seems pretty
harmless in comparison.
Hmm?
But I'll bow to the x86 maintainers.
Linus
next prev parent reply other threads:[~2018-08-31 4:25 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-30 21:45 [PATCH] x86/mce: Fix set_mce_nospec() to avoid #GP fault Tony Luck
2018-08-31 1:29 ` Linus Torvalds
2018-08-31 1:48 ` Tony Luck
2018-08-31 4:25 ` Linus Torvalds [this message]
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 ` [PATCH] " David Laight
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