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Message-ID: <1516616628.9814.149.camel@infradead.org>
Subject: Re: [RFC 04/10] x86/mm: Only flush indirect branches when
 switching into non dumpable process
From:   David Woodhouse <dwmw2@infradead.org>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     hjl.tools@gmail.com, KarimAllah Ahmed <karahmed@amazon.de>,
        linux-kernel@vger.kernel.org, Andi Kleen <ak@linux.intel.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Andy Lutomirski <luto@kernel.org>,
        Arjan van de Ven <arjan@linux.intel.com>,
        Ashok Raj <ashok.raj@intel.com>,
        Asit Mallick <asit.k.mallick@intel.com>,
        Borislav Petkov <bp@suse.de>,
        Dan Williams <dan.j.williams@intel.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "H . Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        Janakarajan Natarajan <janakarajan.natarajan@amd.com>,
        Joerg Roedel <joro@8bytes.org>,
        Jun Nakajima <jun.nakajima@intel.com>,
        Laura Abbott <labbott@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        "\"Radim" =?UTF-8?Q?Kr=C4=8Dm=C3=A1=C5=99=22?= <rkrcmar@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Tom Lendacky <thomas.lendacky@amd.com>, kvm@vger.kernel.org,
        x86@kernel.org
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Date:   Mon, 22 Jan 2018 10:23:48 +0000
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On Mon, 2018-01-22 at 11:19 +0100, Peter Zijlstra wrote:
> Right, so if its v2/retpoline only, we really should do this asap and
> then rebuild world on distros (or arch/gentoo people could read a book
> or something).

By the time we manage to rebuild all the distros, I *seriously* hope
that someone would be shipping a fixed CPU.

And not just the half-way-there IBRS_ALL bit that still requires the
IBPB flushing on context switches that's discussed in this patch, but
an *actual* fix so we can forget about it all and go drinking.
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