4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Thomas Gleixner <t...@linutronix.de>
commit 47c61b3955cf712cadfc25635bf9bc174af030ea upstream
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 <t...@linutronix.de>
Signed-off-by: David Woodhouse <d...@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
arch/x86/include/asm/spec-ctrl.h | 6 ++++++
arch/x86/kernel/cpu/bugs.c | 30 ++++++++++++++++++++++++++++++
2 files changed, 36 insertions(+)
--- a/arch/x86/include/asm/spec-ctrl.h
+++ b/arch/x86/include/asm/spec-ctrl.h
@@ -53,6 +53,12 @@ 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
@@ -161,6 +161,36 @@ x86_virt_spec_ctrl(u64 guest_spec_ctrl,
wrmsrl(MSR_IA32_SPEC_CTRL, msrval);
}
}
+
+ /*
+ * 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 the host has SSBD mitigation enabled, force it in the host's
+ * virtual MSR value. If its not permanently enabled, evaluate
+ * current's TIF_SSBD thread flag.
+ */
+ if (static_cpu_has(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE))
+ hostval = SPEC_CTRL_SSBD;
+ else
+ hostval = ssbd_tif_to_spec_ctrl(ti->flags);
+
+ /* Sanitize the guest value */
+ guestval = guest_virt_spec_ctrl & SPEC_CTRL_SSBD;
+
+ if (hostval != guestval) {
+ unsigned long tif;
+
+ tif = setguest ? ssbd_spec_ctrl_to_tif(guestval) :
+ ssbd_spec_ctrl_to_tif(hostval);
+
+ speculative_store_bypass_update(tif);
+ }
}
EXPORT_SYMBOL_GPL(x86_virt_spec_ctrl);
