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Date: Mon, 9 Mar 2015 17:02:32 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Steven Rostedt <rostedt@goodmis.org>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, Oleg Nesterov <oleg@redhat.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Alexei Starovoitov <ast@plumgrid.com>, Will Drewry <wad@chromium.org>,
        Kees Cook <keescook@chromium.org>, x86@kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] x86: save r11 into pt_regs->flags on SYSCALL64
 fastpath
Message-ID: <20150309160232.GA21787@gmail.com>
References: <1425847750-23362-1-git-send-email-dvlasenk@redhat.com>
 <1425847750-23362-2-git-send-email-dvlasenk@redhat.com>
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* Denys Vlasenko <dvlasenk@redhat.com> wrote:

> Before this patch, r11 was saved in pt_regs->r11.
> Which looks natural, but requires messy shuffling to/from iret frame
> whenever ptrace or e.g. iopl wants to modify flags - because
> that's how this register is used by SYSCALL/SYSRET.
> 
> This patch saves r11 in pt_regs->flags,
> and uses that value for SYSRET64 insn. Shuffling is eliminated.
> 
> stub_iopl is no longer needed: pt_regs->flags needs no fixing up.

Could you please split this into two patches: R11 saving, and 
stub_iopl removal?

For x86/asm changes we want as small changes as physically possible.

Thanks,

	Ingo