From: Oleg Nesterov <oleg@redhat.com>
To: Brian Gerst <brgerst@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@alien8.de>,
Ingo Molnar <mingo@redhat.com>, Peter Anvin <hpa@zytor.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>
Subject: Re: Q: does force_iret() make any sense today?
Date: Wed, 18 Dec 2019 17:06:41 +0100 [thread overview]
Message-ID: <20191218160641.GA29716@redhat.com> (raw)
In-Reply-To: <CAMzpN2gOA=ysOCidCUmxZ6cev5HuKXPdBA_mni5SR01=ii-+KQ@mail.gmail.com>
On 12/18, Brian Gerst wrote:
>
> On Wed, Dec 18, 2019 at 10:31 AM Oleg Nesterov <oleg@redhat.com> wrote:
> >
> > I do not pretend I understand the arch/x86/entry/ code, but it seems that
> > asm does all the necessary checks and the "extra" TIF_NOTIFY_RESUME simply
> > has no effect except tracehook_notify_resume() will be called for no reason?
>
> It's a relic of a time before the more robust checks for
> SYSRET/SYSEXIT were added. The idea was to divert the syscall return
> flow off the fast path. Even if no exit work was done, the slow path
> always returned with IRET. But with all the entry rework that has
> been done it is no longer needed and can be removed.
Thanks, this was my understanding. Will you make a patch?
Oleg.
prev parent reply other threads:[~2019-12-18 16:06 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-18 15:31 Q: does force_iret() make any sense today? Oleg Nesterov
2019-12-18 15:45 ` Brian Gerst
2019-12-18 16:06 ` Oleg Nesterov [this message]
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