From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Josh Poimboeuf <jpoimboe@kernel.org>, x86@kernel.org
Cc: linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Daniel Sneddon <daniel.sneddon@linux.intel.com>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Alexandre Chartre <alexandre.chartre@oracle.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Peter Zijlstra <peterz@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Sean Christopherson <seanjc@google.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Nikolay Borisov <nik.borisov@suse.com>,
KP Singh <kpsingh@kernel.org>, Waiman Long <longman@redhat.com>,
Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH 3/3] x86/bugs: Remove support for Spectre v2 LFENCE "retpolines"
Date: Fri, 12 Apr 2024 21:49:33 +0100 [thread overview]
Message-ID: <b0074626-8e98-4573-8047-08916fbb5537@citrix.com> (raw)
In-Reply-To: <e5356c0e018cd0a96aabe719f685c237ac519403.1712944776.git.jpoimboe@kernel.org>
On 12/04/2024 7:10 pm, Josh Poimboeuf wrote:
> I found several bugs where code assumes that X86_FEATURE_RETPOLINE
> actually means retpolines (imagine that!).
Yeah :( One could also imagine a past where that was pointed out, or
just read about it in the archives.
> In fact that feature also
> includes the original AMD LFENCE "retpolines", which aren't in fact
> retpolines.
>
> Really, those "retpolines" should just be removed. They're already
> considered vulnerable due to the fact that the speculative window after
> the indirect branch can still be long enough to do multiple dependent
> loads. And recent tooling makes such gadgets easier to find.
There are two Atom CPUs which are not repotline safe, and for which
Intel released a statement saying "use lfence/jmp" on these.
I'm still trying to find it...
~Andrew
next prev parent reply other threads:[~2024-04-12 20:49 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-12 18:10 [PATCH 0/3] x86/bugs: BHI fixes / improvements - round 2 Josh Poimboeuf
2024-04-12 18:10 ` [PATCH v2 1/3] x86/bugs: Only harden syscalls when needed Josh Poimboeuf
2024-04-12 22:42 ` Pawan Gupta
2024-04-12 22:58 ` Josh Poimboeuf
2024-04-15 7:32 ` Nikolay Borisov
2024-04-15 15:16 ` Linus Torvalds
2024-04-15 15:27 ` Nikolay Borisov
2024-04-15 15:47 ` Linus Torvalds
2024-04-12 18:10 ` [PATCH 2/3] x86/bugs: Fix BHI retpoline check Josh Poimboeuf
2024-04-12 23:18 ` Pawan Gupta
2024-04-14 9:19 ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
2024-04-12 18:10 ` [PATCH 3/3] x86/bugs: Remove support for Spectre v2 LFENCE "retpolines" Josh Poimboeuf
2024-04-12 18:20 ` Josh Poimboeuf
2024-04-12 20:49 ` Andrew Cooper [this message]
2024-04-15 23:44 ` Josh Poimboeuf
2024-04-13 4:21 ` Josh Poimboeuf
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