linux-kernel - Re: [patch 01/60] x86/entry/64/paravirt: Use paravirt-safe macro to access eflags

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Date:   Tue, 5 Dec 2017 13:17:31 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirsky <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Borislav Petkov <bpetkov@...e.de>,
        Greg KH <gregkh@...uxfoundation.org>, keescook@...gle.com,
        hughd@...gle.com, Brian Gerst <brgerst@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Rik van Riel <riel@...hat.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        David Laight <David.Laight@...lab.com>,
        Eduardo Valentin <eduval@...zon.com>, aliguori@...zon.com,
        Will Deacon <will.deacon@....com>, daniel.gruss@...k.tugraz.at,
        xen-devel@...ts.xenproject.org
Subject: Re: [patch 01/60] x86/entry/64/paravirt: Use paravirt-safe macro to
 access eflags

On 04/12/17 15:07, Thomas Gleixner wrote:
> From: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> 
> Commit 1d3e53e8624a ("x86/entry/64: Refactor IRQ stacks and make them
> NMI-safe") added DEBUG_ENTRY_ASSERT_IRQS_OFF macro that acceses eflags
> using 'pushfq' instruction when testing for IF bit. On PV Xen guests
> looking at IF flag directly will always see it set, resulting in 'ud2'.
> 
> Introduce SAVE_FLAGS() macro that will use appropriate save_fl pv op when
> running paravirt.
> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: jgross@...e.com
> Cc: xen-devel@...ts.xenproject.org
> Cc: luto@...nel.org
> Link: https://lkml.kernel.org/r/1512159805-6314-1-git-send-email-boris.ostrovsky@oracle.com

Reviewed-by: Juergen Gross <jgross@...e.com>


Juergen