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Date:   Tue, 20 Feb 2018 08:44:15 +0100 (CET)
From:   Thomas Gleixner <tglx@linutronix.de>
To:     David Woodhouse <dwmw@amazon.co.uk>
cc:     karahmed@amazon.de, x86@kernel.org, kvm@vger.kernel.org,
        torvalds@linux-foundation.org, pbonzini@redhat.com,
        linux-kernel@vger.kernel.org, bp@alien8.de, peterz@infradead.org,
        jmattson@google.com, rkrcmar@redhat.com,
        arjan.van.de.ven@intel.com, dave.hansen@intel.com, mingo@kernel.org
Subject: Re: [PATCH v3 1/4] x86/speculation: Use IBRS if available before
 calling into firmware
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On Mon, 19 Feb 2018, David Woodhouse wrote:

> Retpoline means the kernel is safe because it has no indirect branches.
> But firmware isn't, so use IBRS for firmware calls if it's available.
> 
> Block preemption while IBRS is set, although in practice the call sites
> already had to be doing that.
> 
> Ignore hpwdt.c for now. It's taking spinlocks and calling into firmware
> code, from an NMI handler. I don't want to touch that with a bargepole.
> 
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>