Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Wed, 5 Oct 2022 13:33:02 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc:     x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-mm@kvack.org,
        linux-arch@vger.kernel.org, linux-api@vger.kernel.org,
        Arnd Bergmann <arnd@arndb.de>,
        Andy Lutomirski <luto@kernel.org>,
        Balbir Singh <bsingharora@gmail.com>,
        Borislav Petkov <bp@alien8.de>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Eugene Syromiatnikov <esyr@redhat.com>,
        Florian Weimer <fweimer@redhat.com>,
        "H . J . Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Kees Cook <keescook@chromium.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Nadav Amit <nadav.amit@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
        Randy Dunlap <rdunlap@infradead.org>,
        "Ravi V . Shankar" <ravi.v.shankar@intel.com>,
        Weijiang Yang <weijiang.yang@intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        joao.moreira@intel.com, John Allen <john.allen@amd.com>,
        kcc@google.com, eranian@google.com, rppt@kernel.org,
        jamorris@linux.microsoft.com, dethoma@microsoft.com,
        Yu-cheng Yu <yu-cheng.yu@intel.com>
Subject: Re: [PATCH v2 10/39] x86/mm: Introduce _PAGE_COW
Message-ID: <Yz1rbqGHOzmu8Hig@hirez.programming.kicks-ass.net>
References: <20220929222936.14584-1-rick.p.edgecombe@intel.com>
 <20220929222936.14584-11-rick.p.edgecombe@intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220929222936.14584-11-rick.p.edgecombe@intel.com>
Precedence: bulk

On Thu, Sep 29, 2022 at 03:29:07PM -0700, Rick Edgecombe wrote:

Mucho confusion here:

> (a) (Write=0,Cow=1,Dirty=0) A modified, copy-on-write (COW) page.
> (b) (Write=0,Cow=1,Dirty=0) A R/O page that has been COW'ed. The user page
> (d) (Write=0,Cow=1,Dirty=0) A shared shadow stack PTE. When a shadow stack

are all identical cases;

> (c) (Write=0,Cow=0,Dirty=1) A shadow stack PTE.
> (e) (Write=0,Cow=0,Dirty=1) A Cow PTE created when a processor without

as are these.