Restructure mmio mitigation to use select/update/apply functions to
create consistent vulnerability handling.

Signed-off-by: David Kaplan <david.kaplan@amd.com>
---
 arch/x86/kernel/cpu/bugs.c | 55 +++++++++++++++++++++++++++-----------
 1 file changed, 39 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index c676804dfd84..1332b70e48f8 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -68,6 +68,8 @@ static void __init taa_select_mitigation(void);
 static void __init taa_update_mitigation(void);
 static void __init taa_apply_mitigation(void);
 static void __init mmio_select_mitigation(void);
+static void __init mmio_update_mitigation(void);
+static void __init mmio_apply_mitigation(void);
 static void __init srbds_select_mitigation(void);
 static void __init l1d_flush_select_mitigation(void);
 static void __init srso_select_mitigation(void);
@@ -190,6 +192,7 @@ void __init cpu_select_mitigations(void)
 	l1tf_select_mitigation();
 	mds_select_mitigation();
 	taa_select_mitigation();
+	mmio_select_mitigation();
 	md_clear_select_mitigation();
 	srbds_select_mitigation();
 	l1d_flush_select_mitigation();
@@ -207,9 +210,11 @@ void __init cpu_select_mitigations(void)
 	 */
 	mds_update_mitigation();
 	taa_update_mitigation();
+	mmio_update_mitigation();
 
 	mds_apply_mitigation();
 	taa_apply_mitigation();
+	mmio_apply_mitigation();
 }
 
 /*
@@ -505,6 +510,40 @@ static void __init mmio_select_mitigation(void)
 		return;
 	}
 
+	if (mmio_mitigation == MMIO_MITIGATION_OFF)
+		return;
+
+	/*
+	 * Check if the system has the right microcode.
+	 *
+	 * CPU Fill buffer clear mitigation is enumerated by either an explicit
+	 * FB_CLEAR or by the presence of both MD_CLEAR and L1D_FLUSH on MDS
+	 * affected systems.
+	 */
+	if ((x86_arch_cap_msr & ARCH_CAP_FB_CLEAR) ||
+	    (boot_cpu_has(X86_FEATURE_MD_CLEAR) &&
+	     boot_cpu_has(X86_FEATURE_FLUSH_L1D) &&
+	     !(x86_arch_cap_msr & ARCH_CAP_MDS_NO)))
+		mmio_mitigation = MMIO_MITIGATION_VERW;
+	else
+		mmio_mitigation = MMIO_MITIGATION_UCODE_NEEDED;
+}
+
+static void __init mmio_update_mitigation(void)
+{
+	if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
+		return;
+
+	if (mitigate_any_verw())
+		mmio_mitigation = MMIO_MITIGATION_VERW;
+
+	pr_info("%s\n", mmio_strings[mmio_mitigation]);
+	if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN))
+		pr_info("Unknown: No mitigations\n");
+}
+
+static void __init mmio_apply_mitigation(void)
+{
 	if (mmio_mitigation == MMIO_MITIGATION_OFF)
 		return;
 
@@ -533,21 +572,6 @@ static void __init mmio_select_mitigation(void)
 	if (!(x86_arch_cap_msr & ARCH_CAP_FBSDP_NO))
 		static_branch_enable(&mds_idle_clear);
 
-	/*
-	 * Check if the system has the right microcode.
-	 *
-	 * CPU Fill buffer clear mitigation is enumerated by either an explicit
-	 * FB_CLEAR or by the presence of both MD_CLEAR and L1D_FLUSH on MDS
-	 * affected systems.
-	 */
-	if ((x86_arch_cap_msr & ARCH_CAP_FB_CLEAR) ||
-	    (boot_cpu_has(X86_FEATURE_MD_CLEAR) &&
-	     boot_cpu_has(X86_FEATURE_FLUSH_L1D) &&
-	     !(x86_arch_cap_msr & ARCH_CAP_MDS_NO)))
-		mmio_mitigation = MMIO_MITIGATION_VERW;
-	else
-		mmio_mitigation = MMIO_MITIGATION_UCODE_NEEDED;
-
 	if (mmio_nosmt || cpu_mitigations_auto_nosmt())
 		cpu_smt_disable(false);
 }
@@ -670,7 +694,6 @@ static void __init md_clear_update_mitigation(void)
 
 static void __init md_clear_select_mitigation(void)
 {
-	mmio_select_mitigation();
 	rfds_select_mitigation();
 
 	/*
-- 
2.34.1

On Tue, Nov 05, 2024 at 03:54:26PM -0600, David Kaplan wrote:
> +static void __init mmio_update_mitigation(void)
> +{
> +	if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
> +		return;
> +
> +	if (mitigate_any_verw())
> +		mmio_mitigation = MMIO_MITIGATION_VERW;

Same as TAA, UCODE_NEEDED can't be set irrespective of microcode.

> +
> +	pr_info("%s\n", mmio_strings[mmio_mitigation]);

This should be in the 'else' part of below condition, otherwise they can
print conflicting mitigation status.

> +	if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN))
> +		pr_info("Unknown: No mitigations\n");
> +}