From: Gleb Natapov <gleb@redhat.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
KVM list <kvm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Peter Anvin <hpa@zytor.com>
Subject: Re: [PATCH, RFC] x86-64: properly handle FPU code/data selectors
Date: Thu, 17 Oct 2013 12:27:27 +0300 [thread overview]
Message-ID: <20131017092727.GN15657@redhat.com> (raw)
In-Reply-To: <525ED75402000078000FB95B@nat28.tlf.novell.com>
On Wed, Oct 16, 2013 at 05:13:40PM +0100, Jan Beulich wrote:
> > It preserves *less* state, because the upper 32 bits of rip are now
> > corrupted. Any 64-bit application that actually looks at the FP
> > rip/rdp fields now get the WRONG VALUES.
>
> But again - this isn't being done for ordinary 64-bit applications,
> this is only happening for KVM guests. And there not being a
> protocol for telling the caller whether a certain context hold
> 64-bit offsets or selector/offset pairs shouldn't be a reason to
> think of a solution to the problem.
>
KVM knows what mode guest vcpu is in. is_long_mode(vcpu) will tell you
if it is in long mode or not. No need to guess it.
--
Gleb.
next prev parent reply other threads:[~2013-10-17 9:27 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-16 12:00 [PATCH, RFC] x86-64: properly handle FPU code/data selectors Jan Beulich
2013-10-16 15:19 ` Linus Torvalds
2013-10-16 15:36 ` Jan Beulich
2013-10-16 15:50 ` Linus Torvalds
2013-10-16 16:13 ` Jan Beulich
2013-10-16 18:43 ` Linus Torvalds
2013-10-17 7:09 ` Jan Beulich
2013-10-17 9:27 ` Gleb Natapov [this message]
2013-10-17 9:33 ` Jan Beulich
2013-10-17 9:41 ` Gleb Natapov
2013-10-17 9:51 ` Jan Beulich
2013-10-17 10:23 ` Gleb Natapov
2013-10-17 10:37 ` Jan Beulich
2013-10-17 10:39 ` Gleb Natapov
2013-10-16 15:39 ` H. Peter Anvin
2013-10-16 16:07 ` Jan Beulich
2013-10-16 17:13 ` H. Peter Anvin
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