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

From: Thomas Gleixner
Date: Mon Aug 20 2018 - 12:01:11 EST

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@xxxxxxxxxx>
> Reviewed-by: Peter Shier <pshier@xxxxxxxxxx>

That has been superseeded by:

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

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