From: Thomas Gleixner <tglx@linutronix.de>
To: Juergen Gross <jgross@suse.com>
Cc: linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org,
x86@kernel.org, boris.ostrovsky@oracle.com, hpa@zytor.com,
mingo@redhat.com
Subject: Re: [PATCH v3] x86/amd: don't set X86_BUG_SYSRET_SS_ATTRS when running under Xen
Date: Thu, 11 May 2017 14:46:58 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.20.1705111446430.1758@nanos> (raw)
In-Reply-To: <566478e1-3a1c-2800-8662-09a6ad31a7b6@suse.com>
On Thu, 11 May 2017, Juergen Gross wrote:
> On 27/04/17 07:01, Juergen Gross wrote:
> > When running as Xen pv guest X86_BUG_SYSRET_SS_ATTRS must not be set
> > on AMD cpus.
> >
> > This bug/feature bit is kind of special as it will be used very early
> > when switching threads. Setting the bit and clearing it a little bit
> > later leaves a critical window where things can go wrong. This time
> > window has enlarged a little bit by using setup_clear_cpu_cap() instead
> > of the hypervisor's set_cpu_features callback. It seems this larger
> > window now makes it rather easy to hit the problem.
> >
> > The proper solution is to never set the bit in case of Xen.
> >
> > Signed-off-by: Juergen Gross <jgross@suse.com>
>
> Any objections for carrying this through the Xen tree?
Acked-by: Thomas Gleixner <tglx@linutronix.de>
prev parent reply other threads:[~2017-05-11 12:47 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-27 5:01 Juergen Gross
2017-05-05 5:09 ` Juergen Gross
2017-05-05 16:02 ` Boris Ostrovsky
2017-05-11 10:31 ` Juergen Gross
2017-05-11 12:46 ` Thomas Gleixner [this message]
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