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Date:   Sun, 11 Feb 2018 12:46:43 +0100
From:   Ingo Molnar <mingo@kernel.org>
To:     David Woodhouse <dwmw@amazon.co.uk>
Cc:     tglx@linutronix.de, karahmed@amazon.de, sironi@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
Subject: Re: [PATCH v2 6/6] x86/speculation: Use IBRS if available before
 calling into firmware
Message-ID: <20180211114643.mek3zydznbernsdr@gmail.com>
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* David Woodhouse <dwmw@amazon.co.uk> 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.

Ok, this approach looks good to me in principle, but:

> --- a/arch/x86/include/asm/apm.h
> +++ b/arch/x86/include/asm/apm.h
> @@ -7,6 +7,8 @@
>  #ifndef _ASM_X86_MACH_DEFAULT_APM_H
>  #define _ASM_X86_MACH_DEFAULT_APM_H
>  
> +#include <asm/spec_ctrl.h>

I cannot see this header file upstream anywhere, nor in any other patch in my mbox 
- is there some dependency that has to be applied first?

Thanks,

	Ingo