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Date:   Tue, 10 Oct 2023 17:48:50 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     Matthew Maurer <mmaurer@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        Miguel Ojeda <ojeda@kernel.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        =?iso-8859-1?Q?Bj=F6rn?= Roy Baron <bjorn3_gh@protonmail.com>,
        Benno Lossin <benno.lossin@proton.me>,
        Andreas Hindborg <a.hindborg@samsung.com>,
        Alice Ryhl <aliceryhl@google.com>,
        linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org
Subject: Re: [PATCH] x86: Enable IBT in Rust if enabled in C
Message-ID: <20231010154850.GR377@noisy.programming.kicks-ass.net>
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On Tue, Oct 10, 2023 at 08:38:58AM -0700, Nick Desaulniers wrote:
> On Tue, Oct 10, 2023 at 1:13 AM Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > On Mon, Oct 09, 2023 at 10:42:54PM +0000, Matthew Maurer wrote:
> > > These flags are not made conditional on compiler support because at the
> > > moment exactly one version of rustc supported, and that one supports
> > > these flags.
> > >
> > > Building without these additional flags will manifest as objtool
> > > printing a large number of errors about missing ENDBR and if CFI is
> > > enabled (not currently possible) will result in incorrectly structured
> > > function prefixes.
> >
> > Well, I would also imagine running it on actual IBT enabled hardware
> > will get you a non-booting kernel.
> 
> Do you know what machine type in QEMU first supports IBT?

I'm not sure QEMU has IBT support at all atm -- the whole CET
virtualization stuff is a bit of a mess.

But hardware wise it's Tigerlake (11) and everything after that - so
Alderlake (12) and Saphire Rapids (4th gen scalable -- or somesuch
nonsense).