Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20201023203154.27335-1-linux@rasmusvillemoes.dk>
In-Reply-To: <20201023203154.27335-1-linux@rasmusvillemoes.dk>
From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 23 Oct 2020 13:55:22 -0700
Message-ID: <CAHk-=wj1m3cvS-3dOYzNavYWLFu=9fwo0-6HTHJhG-X5B73gZg@mail.gmail.com>
Subject: Re: [PATCH] x86/uaccess: fix code generation in put_user()
To:     Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Naresh Kamboju <naresh.kamboju@linaro.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Thanks, applied.

On Fri, Oct 23, 2020 at 1:32 PM Rasmus Villemoes
<linux@rasmusvillemoes.dk> wrote:
>
> I'm wondering if one would also need to make __ptr_pu and __ret_pu
> explicitly "%"_ASM_CX".

No, the "c"/"0" thing is much better, and makes it properly atomic wrt
the actual asm.

As mentioned to Andy, the "register asm()" thing is not uncommon and
often useful, but when you can specify the register directly in asm,
that's certainly simpler and more straightforward and preferred.

              Linus