Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Mon, 20 Aug 2018 18:24:50 +0200 (CEST)
From:   Thomas Gleixner <tglx@linutronix.de>
To:     Jim Mattson <jmattson@google.com>
cc:     Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
        the arch/x86 maintainers <x86@kernel.org>,
        Borislav Petkov <bp@suse.de>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        David Woodhouse <dwmw@amazon.co.uk>,
        LKML <linux-kernel@vger.kernel.org>,
        Fred Jacobs <fjacobs@vmware.com>,
        Peter Shier <pshier@google.com>
Subject: Re: [PATCH] x86/spectre: Expand test for vulnerability to empty RSB
 exploits
In-Reply-To: <CALMp9eTSNA_52tdgqeqMpBYMkPTvhGtwwWyGMwQKH3cyiS0agA@mail.gmail.com>
Message-ID: <alpine.DEB.2.21.1808201823560.1551@nanos.tec.linutronix.de>
References: <20180807222535.143193-1-jmattson@google.com> <alpine.DEB.2.21.1808201758250.1551@nanos.tec.linutronix.de> <CALMp9eTSNA_52tdgqeqMpBYMkPTvhGtwwWyGMwQKH3cyiS0agA@mail.gmail.com>
User-Agent: Alpine 2.21 (DEB 202 2017-01-01)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, 20 Aug 2018, Jim Mattson wrote:
> On Mon, Aug 20, 2018 at 9:00 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> >
> > 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@google.com>
> > > Reviewed-by: Peter Shier <pshier@google.com>
> >
> > That has been superseeded by:
> >
> >   fdf82a7856b3 ("x86/speculation: Protect against userspace-userspace spectreRSB")
> >
> > right? At least it does not apply anymore...
> 
> Right. It doesn't appear that Skylake CPUs get any special treatment any more.

Yeah, it's universally f*cked up by now.

Thanks,

	tglx