Merge tag 'v5.1.16' into dev-5.1dev-5.1

This is the 5.1.16 stable release

Signed-off-by: Joel Stanley <joel@jms.id.au>

1 files changed, 10 insertions, 1 deletions

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 03b4cc0ec3a7..66ca906aa790 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -836,6 +836,16 @@ static enum ssb_mitigation __init __ssb_select_mitigation(void)
 	}
 
 	/*
+	 * If SSBD is controlled by the SPEC_CTRL MSR, then set the proper
+	 * bit in the mask to allow guests to use the mitigation even in the
+	 * case where the host does not enable it.
+	 */
+	if (static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) ||
+	    static_cpu_has(X86_FEATURE_AMD_SSBD)) {
+		x86_spec_ctrl_mask |= SPEC_CTRL_SSBD;
+	}
+
+	/*
 	 * We have three CPU feature flags that are in play here:
 	 *  - X86_BUG_SPEC_STORE_BYPASS - CPU is susceptible.
 	 *  - X86_FEATURE_SSBD - CPU is able to turn off speculative store bypass
@@ -852,7 +862,6 @@ static enum ssb_mitigation __init __ssb_select_mitigation(void)
 			x86_amd_ssb_disable();
 		} else {
 			x86_spec_ctrl_base |= SPEC_CTRL_SSBD;
-			x86_spec_ctrl_mask |= SPEC_CTRL_SSBD;
 			wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
 		}
 	}