From: Borislav Petkov <bp@alien8.de>
To: Andy Lutomirski <luto@amacapital.net>
Cc: LKML <linux-kernel@vger.kernel.org>,
Andy Lutomirski <luto@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [RFC PATCH] x86/cpu: Fix MSR value truncation issue
Date: Wed, 11 Nov 2015 17:05:15 +0100 [thread overview]
Message-ID: <20151111160515.GH22512@pd.tnic> (raw)
In-Reply-To: <CALCETrX9dPLO2Qebh3VmCUm=Rf99L-JdgbhfeBGeVJZwrt0oZg@mail.gmail.com>
On Wed, Nov 11, 2015 at 07:50:04AM -0800, Andy Lutomirski wrote:
> Not terribly surprising :) Someone (I forget who) told me that 32-bit
> SYSCALL (native 32-bit, not compat) was so full of errata that it was
> unusable. Even without errata, I don't really see how it would work
> well
No, showstopper appears much earlier: it is only supported on AMD. Which
would mean, yet another vendor special-handling. And I don't think it's
worth it.
Yeah, yeah, it might still be faster than SYSENTER, but 32-bit?! Srsly?!
I'm surprised that thing still builds even. :-)
> -- there's no MSR_SYSCALL_MASK,
Of course there is:
MSRC000_0084 SYSCALL Flag Mask (SYSCALL_FLAG_MASK):
31:0 - Mask: SYSCALL flag mask. Read-write. Reset: 0000_0000h. This register holds the EFLAGS
mask used by the SYSCALL instruction. 1=Clear the corresponding EFLAGS bit when executing the
SYSCALL instruction.
Intel has that too, except again, no SYSCALL in legacy mode on Intel.
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
next prev parent reply other threads:[~2015-11-11 16:05 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-30 17:28 [RFC PATCH] x86/cpu: Fix MSR value truncation issue Borislav Petkov
2015-10-30 18:59 ` Andy Lutomirski
2015-10-30 19:23 ` Borislav Petkov
2015-10-30 19:26 ` Andy Lutomirski
2015-10-30 19:32 ` Borislav Petkov
2015-10-30 19:34 ` Andy Lutomirski
2015-10-31 11:46 ` [PATCH] x86/MSR: Chop off lower 32-bit value Borislav Petkov
2015-11-11 12:31 ` [RFC PATCH] x86/cpu: Fix MSR value truncation issue Borislav Petkov
2015-11-11 15:50 ` Andy Lutomirski
2015-11-11 16:05 ` Borislav Petkov [this message]
2015-11-11 18:07 ` Brian Gerst
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