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Message-ID: <123f9a29-ddcd-13e5-68a1-22c6d938d76c@intel.com>
Date:   Wed, 9 Feb 2022 13:55:52 -0800
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Subject: Re: [PATCH 14/35] mm: Introduce VM_SHADOW_STACK for shadow stack
 memory
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To:     Rick Edgecombe <rick.p.edgecombe@intel.com>, 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>,
        Peter Zijlstra <peterz@infradead.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        "Ravi V . Shankar" <ravi.v.shankar@intel.com>,
        Dave Martin <Dave.Martin@arm.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
Cc:     Yu-cheng Yu <yu-cheng.yu@intel.com>
References: <20220130211838.8382-1-rick.p.edgecombe@intel.com>
 <20220130211838.8382-15-rick.p.edgecombe@intel.com>
From:   Dave Hansen <dave.hansen@intel.com>
In-Reply-To: <20220130211838.8382-15-rick.p.edgecombe@intel.com>
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On 1/30/22 13:18, Rick Edgecombe wrote:
> A shadow stack PTE must be read-only and have _PAGE_DIRTY set.  However,
> read-only and Dirty PTEs also exist for copy-on-write (COW) pages.  These
> two cases are handled differently for page faults.  Introduce
> VM_SHADOW_STACK to track shadow stack VMAs.

This is also a very appropriate place to remind folks that VM_WRITE is
mutually exclusive with this flag.  That's pretty important.