x86/bugs: Remove X86_BUG_MMIO_UNKNOWN

Whack this thing because:

- the "unknown" handling is done only for this vuln and not for the
  others

- it doesn't do anything besides reporting things differently. It
  doesn't apply any mitigations - it is simply causing unnecessary
  complications to the code which don't bring anything besides
  maintenance overhead to what is already a very nasty spaghetti pile

- all the currently unaffected CPUs can also be in "unknown" status so
  there's no need for special handling here

so get rid of it.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: David Kaplan <david.kaplan@amd.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Link: https://lore.kernel.org/r/20250414150951.5345-1-bp@kernel.org

1 files changed, 1 insertions, 11 deletions

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 4386aa6c69e1..a91a1cac6183 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -428,7 +428,6 @@ static const char * const mmio_strings[] = {
 static void __init mmio_select_mitigation(void)
 {
 	if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA) ||
-	     boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN) ||
 	     cpu_mitigations_off()) {
 		mmio_mitigation = MMIO_MITIGATION_OFF;
 		return;
@@ -591,8 +590,6 @@ out:
 		pr_info("TAA: %s\n", taa_strings[taa_mitigation]);
 	if (boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
 		pr_info("MMIO Stale Data: %s\n", mmio_strings[mmio_mitigation]);
-	else if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN))
-		pr_info("MMIO Stale Data: Unknown: No mitigations\n");
 	if (boot_cpu_has_bug(X86_BUG_RFDS))
 		pr_info("Register File Data Sampling: %s\n", rfds_strings[rfds_mitigation]);
 }
@@ -2819,9 +2816,6 @@ static ssize_t tsx_async_abort_show_state(char *buf)
 
 static ssize_t mmio_stale_data_show_state(char *buf)
 {
-	if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN))
-		return sysfs_emit(buf, "Unknown: No mitigations\n");
-
 	if (mmio_mitigation == MMIO_MITIGATION_OFF)
 		return sysfs_emit(buf, "%s\n", mmio_strings[mmio_mitigation]);
 
@@ -3006,7 +3000,6 @@ static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr
 		return srbds_show_state(buf);
 
 	case X86_BUG_MMIO_STALE_DATA:
-	case X86_BUG_MMIO_UNKNOWN:
 		return mmio_stale_data_show_state(buf);
 
 	case X86_BUG_RETBLEED:
@@ -3075,10 +3068,7 @@ ssize_t cpu_show_srbds(struct device *dev, struct device_attribute *attr, char *
 
 ssize_t cpu_show_mmio_stale_data(struct device *dev, struct device_attribute *attr, char *buf)
 {
-	if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN))
-		return cpu_show_common(dev, attr, buf, X86_BUG_MMIO_UNKNOWN);
-	else
-		return cpu_show_common(dev, attr, buf, X86_BUG_MMIO_STALE_DATA);
+	return cpu_show_common(dev, attr, buf, X86_BUG_MMIO_STALE_DATA);
 }
 
 ssize_t cpu_show_retbleed(struct device *dev, struct device_attribute *attr, char *buf)