linux-kernel - Re: [PATCH v2] x86/entry/64/paravirt: Use paravirt-safe macro to access eflags

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Date:   Wed, 29 Nov 2017 08:25:53 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, luto@...nel.org
Subject: Re: [PATCH v2] x86/entry/64/paravirt: Use paravirt-safe macro to
 access eflags

On 28/11/17 16:28, Boris Ostrovsky wrote:
> 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>

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


Juergen