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Date:   Fri, 20 Dec 2019 20:35:44 +0100
From:   Oleg Nesterov <oleg@redhat.com>
To:     Brian Gerst <brgerst@gmail.com>
Cc:     x86@kernel.org, linux-kernel@vger.kernel.org,
        Ingo Molnar <mingo@kernel.org>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: Re: [PATCH] x86: Remove force_iret()
Message-ID: <20191220193543.GD13464@redhat.com>
References: <20191219115812.102620-1-brgerst@gmail.com>
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On 12/19, Brian Gerst wrote:
>
> force_iret() was originally intended to prevent the return to user mode with
> the SYSRET or SYSEXIT instructions, in cases where the register state could
> have been changed to be incompatible with those instructions.  The entry code
> has been significantly reworked since then, and register state is validated
> before SYSRET or SYSEXIT are used.  force_iret() no longer serves its original
> purpose and can be eliminated.

Plus iiuc today force_iret() == set_thread_flag(TIF_NOTIFY_RESUME) simply has
no effect on asm paths.

Acked-by: Oleg Nesterov <oleg@redhat.com>