linux-kernel - [PATCH] Fix SSBD not being exposed to guests. (v1)

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Date:   Mon, 21 May 2018 17:54:48 -0400
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] Fix SSBD not being exposed to guests. (v1)

Hi,

Without this patch, when launching QEMU with -cpu +ssbd I ended up
with a warning seeing that the CPU does not support - which in fact it does.

The issue was the X86_FEATURE_ -  the kvm_cpuid_7_0_edx_x86_features
had bit 17 set (X86_FEATURE_SSBD), while the right bit should have been
bit 31 ( X86_FEATURE_SPEC_CTRL_SSBD). That meant the masking:

	entry->edx &= kvm_cpuid_7_0_edx_x86_features;

would nicely clear the SSBD bit.

This fixes:
Fixes: 52817587e706 ("x86/cpufeatures: Disentangle SSBD enumeration")

 arch/x86/kvm/cpuid.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Konrad Rzeszutek Wilk (1):
      KVM: VMX: Expose SSBD properly to guests.