linux-kernel - Re: [PATCH] x86/spectre: Expand test for vulnerability to empty RSB exploits

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Message-ID: <alpine.DEB.2.21.1808201758250.1551@nanos.tec.linutronix.de>
Date:   Mon, 20 Aug 2018 18:00:51 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Jim Mattson <jmattson@...gle.com>
cc:     Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
        x86@...nel.org, Borislav Petkov <bp@...e.de>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        linux-kernel@...r.kernel.org, Fred Jacobs <fjacobs@...are.com>,
        Peter Shier <pshier@...gle.com>
Subject: Re: [PATCH] x86/spectre: Expand test for vulnerability to empty RSB
 exploits

On Tue, 7 Aug 2018, Jim Mattson wrote:

> Skylake-era Intel CPUs are vulnerable to exploits of empty RSB
> conditions. On hardware, platform vulnerability can be determined
> simply by checking the processor's DisplayModel/DisplayFamily
> signature.  However, when running in a VM, the operating system should
> also query IA32_ARCH_CAPABILITIES.RSBA[bit 2], a synthetic bit that
> can be set by a hypervisor to indicate that the VM might run on a
> vulnerable physical processor, regardless of the
> DisplayModel/DisplayFamily reported by CPUID.
> 
> Note that IA32_ARCH_CAPABILITIES.RSBA[bit 2] is always clear on
> hardware, so the DisplayModel/DisplayFamily check is still required.
> 
> For all of the details, see the Intel white paper, "Retpoline: A
> Branch Target Injection Mitigation" (document number 337131-001),
> section 5.3: Virtual Machine CPU Identification.
> 
> Signed-off-by: Jim Mattson <jmattson@...gle.com>
> Reviewed-by: Peter Shier <pshier@...gle.com>

That has been superseeded by:

  fdf82a7856b3 ("x86/speculation: Protect against userspace-userspace spectreRSB")

right? At least it does not apply anymore...

Thanks,

	tglx