From: Arjan van de Ven <arjan@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>,
linux-kernel@vger.kernel.org,
KarimAllah Ahmed <karahmed@amazon.de>,
Andi Kleen <ak@linux.intel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Andy Lutomirski <luto@kernel.org>,
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>,
David Woodhouse <dwmw@amazon.co.uk>,
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>,
rkrcmar@redhat.com, Thomas Gleixner <tglx@linutronix.de>,
Tom Lendacky <thomas.lendacky@amd.com>,
x86@kernel.org
Subject: Re: [RFC PATCH 1/2] x86/ibpb: Skip IBPB when we switch back to same user process
Date: Thu, 25 Jan 2018 09:24:53 -0800 [thread overview]
Message-ID: <565574d1-c0a6-684d-a387-12f2cdaf01de@linux.intel.com> (raw)
In-Reply-To: <20180125164139.GM2269@hirez.programming.kicks-ass.net>
> The idea is simple, do what we do for virt. Don't send IPI's to CPUs
> that don't need them (in virt's case because the vCPU isn't running, in
> our case because we're not in fact running a user process), but mark the
> CPU as having needed a TLB flush.
I am really uncomfortable with that idea.
You really can't run code safely on a cpu where the TLBs in the CPU are invalid
or where a CPU that does (partial) page walks would install invalid PTEs either
through actual or through speculative execution.
(in the virt case there's a cheat, since the code is not actually running
there isn't a cpu with TLBs live. You can't do that same cheat for this case)
prev parent reply other threads:[~2018-01-25 17:24 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-25 0:36 Tim Chen
2018-01-25 0:36 ` [RFC PATCH 2/2] x86/ibpb: Prevent missed IBPB flush Tim Chen
2018-01-25 8:20 ` David Woodhouse
2018-01-25 16:56 ` Tim Chen
2018-01-25 8:58 ` [RFC PATCH 1/2] x86/ibpb: Skip IBPB when we switch back to same user process Peter Zijlstra
2018-01-25 9:22 ` Peter Zijlstra
2018-01-25 13:21 ` Arjan van de Ven
2018-01-25 13:50 ` Peter Zijlstra
2018-01-25 14:07 ` Arjan van de Ven
2018-01-25 16:41 ` Peter Zijlstra
2018-01-25 17:04 ` Andy Lutomirski
2018-01-25 18:18 ` Peter Zijlstra
2018-01-25 19:32 ` Tim Chen
2018-01-25 19:34 ` Arjan van de Ven
2018-01-25 19:45 ` Dave Hansen
2018-01-25 20:46 ` Peter Zijlstra
2018-01-25 21:04 ` Andy Lutomirski
2018-01-25 21:57 ` Andi Kleen
2018-01-25 22:01 ` Andy Lutomirski
2018-01-25 23:07 ` Tim Chen
2018-01-26 0:01 ` Peter Zijlstra
2018-01-25 17:24 ` Arjan van de Ven [this message]
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