[patch 14/15] Hidden 14

[Thomas Gleixner <tglx@linutronix.de>]

Add the necessary logic for supporting the emulated VIRT_SPEC_CTRL MSR to
x86_virt_spec_ctrl().  If either X86_FEATURE_LS_CFG_SSBD or
X86_FEATURE_VIRT_SPEC_CTRL is set then use the new guest_virt_spec_ctrl
argument to check whether the state must be modified on the host. The
update reuses speculative_store_bypass_update() so the ZEN-specific sibling
coordination can be reused.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/include/asm/spec-ctrl.h |    6 ++++++
 arch/x86/kernel/cpu/bugs.c       |   24 ++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

--- a/arch/x86/include/asm/spec-ctrl.h
+++ b/arch/x86/include/asm/spec-ctrl.h
@@ -56,6 +56,12 @@ static inline u64 ssbd_tif_to_spec_ctrl(
 	return (tifn & _TIF_SSBD) >> (TIF_SSBD - SPEC_CTRL_SSBD_SHIFT);
 }
 
+static inline unsigned long ssbd_spec_ctrl_to_tif(u64 spec_ctrl)
+{
+	BUILD_BUG_ON(TIF_SSBD < SPEC_CTRL_SSBD_SHIFT);
+	return (spec_ctrl & SPEC_CTRL_SSBD) << (TIF_SSBD - SPEC_CTRL_SSBD_SHIFT);
+}
+
 static inline u64 ssbd_tif_to_amd_ls_cfg(u64 tifn)
 {
 	return (tifn & _TIF_SSBD) ? x86_amd_ls_cfg_ssbd_mask : 0ULL;
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -162,6 +162,30 @@ x86_virt_spec_ctrl(u64 guest_spec_ctrl,
 			wrmsrl(MSR_IA32_SPEC_CTRL, msr);
 		}
 	}
+
+	/*
+	 * If SSBD is not handled in MSR_SPEC_CTRL on AMD update
+	 * MSR_AMD64_L2_CFG or MSR_VIRT_SPEC_CTRL if supported.
+	 */
+	if (!static_cpu_has(X86_FEATURE_LS_CFG_SSBD) &&
+	    !static_cpu_has(X86_FEATURE_VIRT_SSBD))
+		return;
+
+	/* If host has SSBD disabled via command line, force it */
+	if (static_cpu_has(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE))
+		hostssbd |= SPEC_CTRL_SSBD;
+
+	/* Sanitize the guest value */
+	guest = guest_virt_spec_ctrl & SPEC_CTRL_SSBD;
+
+	if (hostssbd != guest) {
+		unsigned long tif;
+
+		tif = setguest ? ssbd_spec_ctrl_to_tif(guest) :
+				 ssbd_spec_ctrl_to_tif(hostssbd);
+
+		speculative_store_bypass_update(tif);
+	}
 }
 EXPORT_SYMBOL_GPL(x86_virt_spec_ctrl);