Date: Fri, 5 Jun 2015 09:13:20 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
        Andrew Cooper <andrew.cooper3@citrix.com>,
        Xen-devel <xen-devel@lists.xen.org>,
        David Vrabel <david.vrabel@citrix.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        x86@kernel.org, linux-kernel@vger.kernel.org,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>, lguest@lists.ozlabs.org,
        stable@vger.kernel.org
Subject: Re: [PATCH] x86/cpu: Fix SMAP check in PVOPS environments
Message-ID: <20150605071319.GA20449@gmail.com>
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 <5570131C.1000704@citrix.com>
 <873827uu2i.fsf@rustcorp.com.au>
 <5570B51F.4060908@zytor.com>
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* Rusty Russell <rusty@rustcorp.com.au> wrote:

> As the comment in arch/x86/include/asm/paravirt_types.h says:
> 
> 	 * Get/set interrupt state.  save_fl and restore_fl are only
> 	 * expected to use X86_EFLAGS_IF; all other bits
> 	 * returned from save_fl are undefined, and may be ignored by
> 	 * restore_fl.

There should be no 'may' about this: under CONFIG_PARAVIRT_DEBUG=y the reminder of 
the flags should be cleared (or all bits should be set: that will instantly crash 
if restored verbatim), so that we trip up generic code that relies on non-IF 
restoration?

Thanks,

	Ingo
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