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: <YSkz025ncjhyRmlB@zeniv-ca.linux.org.uk> <CAHk-=wh5p6zpgUUoY+O7e74X9BZyODhnsqvv=xqnTaLRNj3d_Q@mail.gmail.com>
 <YSk7xfcHVc7CxtQO@zeniv-ca.linux.org.uk> <CAHk-=wjMyZLH+ta5SohAViSc10iPj-hRnHc-KPDoj1XZCmxdBg@mail.gmail.com>
 <YSk+9cTMYi2+BFW7@zeniv-ca.linux.org.uk> <YSldx9uhMYhT/G8X@zeniv-ca.linux.org.uk>
 <YSlftta38M4FsWUq@zeniv-ca.linux.org.uk> <20210827232246.GA1668365@agluck-desk2.amr.corp.intel.com>
 <87r1edgs2w.ffs@tglx> <YSqy+U/3lnF6K0ia@zeniv-ca.linux.org.uk> <YSq0mPAIBfqFC/NE@zeniv-ca.linux.org.uk>
In-Reply-To: <YSq0mPAIBfqFC/NE@zeniv-ca.linux.org.uk>
From:   Tony Luck <tony.luck@intel.com>
Date:   Sat, 28 Aug 2021 15:20:58 -0700
Message-ID: <CA+8MBbLLze0siip=h-2hR3XiceBFQCN7uh5BPvqYRyBXgT318g@mail.gmail.com>
Subject: Re: [PATCH v7 05/19] iov_iter: Introduce fault_in_iov_iter_writeable
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andreas Gruenbacher <agruenba@redhat.com>,
        Christoph Hellwig <hch@infradead.org>,
        "Darrick J. Wong" <djwong@kernel.org>, Jan Kara <jack@suse.cz>,
        Matthew Wilcox <willy@infradead.org>,
        cluster-devel <cluster-devel@redhat.com>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        ocfs2-devel@oss.oracle.com, Borislav Petkov <bp@alien8.de>,
        X86-ML <x86@kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Sat, Aug 28, 2021 at 3:12 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
> BTW, is #MC triggered on stored to a poisoned cacheline?  Existence of CLZERO
> would seem to argue against that...

No #MC on stores. Just on loads. Note that you can't clear poison
state with a series of small writes to the cache line. But a single
64-byte store might do it (architects didn't want to guarantee that
it would work when I asked about avx512 stores to clear poison
many years ago).

-Tony