From: Borislav Petkov (AMD) Date: Mon, 14 Apr 2025 15:09:51 +0000 (+0200) Subject: x86/bugs: Remove X86_BUG_MMIO_UNKNOWN X-Git-Tag: v6.16-rc1~195^2~29^2~7 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=dd86a1d013e0c94fedd060514b9e7be2988ef320;p=thirdparty%2Flinux.git 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) Signed-off-by: Ingo Molnar Cc: Andrew Cooper Cc: David Kaplan Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Pawan Gupta Link: https://lore.kernel.org/r/20250414150951.5345-1-bp@kernel.org --- diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index 6c2c152d8a67b..e8f8d43a3825d 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -519,7 +519,7 @@ #define X86_BUG_ITLB_MULTIHIT X86_BUG(23) /* "itlb_multihit" CPU may incur MCE during certain page attribute changes */ #define X86_BUG_SRBDS X86_BUG(24) /* "srbds" CPU may leak RNG bits if not mitigated */ #define X86_BUG_MMIO_STALE_DATA X86_BUG(25) /* "mmio_stale_data" CPU is affected by Processor MMIO Stale Data vulnerabilities */ -#define X86_BUG_MMIO_UNKNOWN X86_BUG(26) /* "mmio_unknown" CPU is too old and its MMIO Stale Data status is unknown */ +/* unused, was #define X86_BUG_MMIO_UNKNOWN X86_BUG(26) "mmio_unknown" CPU is too old and its MMIO Stale Data status is unknown */ #define X86_BUG_RETBLEED X86_BUG(27) /* "retbleed" CPU is affected by RETBleed */ #define X86_BUG_EIBRS_PBRSB X86_BUG(28) /* "eibrs_pbrsb" EIBRS is vulnerable to Post Barrier RSB Predictions */ #define X86_BUG_SMT_RSB X86_BUG(29) /* "smt_rsb" CPU is vulnerable to Cross-Thread Return Address Predictions */ diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 4386aa6c69e12..a91a1cac61837 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) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 12126adbc3a9a..4ada55f126ae9 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1402,15 +1402,10 @@ static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c) * Affected CPU list is generally enough to enumerate the vulnerability, * but for virtualization case check for ARCH_CAP MSR bits also, VMM may * not want the guest to enumerate the bug. - * - * Set X86_BUG_MMIO_UNKNOWN for CPUs that are neither in the blacklist, - * nor in the whitelist and also don't enumerate MSR ARCH_CAP MMIO bits. */ if (!arch_cap_mmio_immune(x86_arch_cap_msr)) { if (cpu_matches(cpu_vuln_blacklist, MMIO)) setup_force_cpu_bug(X86_BUG_MMIO_STALE_DATA); - else if (!cpu_matches(cpu_vuln_whitelist, NO_MMIO)) - setup_force_cpu_bug(X86_BUG_MMIO_UNKNOWN); } if (!cpu_has(c, X86_FEATURE_BTC_NO)) { diff --git a/tools/arch/x86/include/asm/cpufeatures.h b/tools/arch/x86/include/asm/cpufeatures.h index 9e3fa7942e7d3..e88500d903093 100644 --- a/tools/arch/x86/include/asm/cpufeatures.h +++ b/tools/arch/x86/include/asm/cpufeatures.h @@ -508,7 +508,7 @@ #define X86_BUG_ITLB_MULTIHIT X86_BUG(23) /* "itlb_multihit" CPU may incur MCE during certain page attribute changes */ #define X86_BUG_SRBDS X86_BUG(24) /* "srbds" CPU may leak RNG bits if not mitigated */ #define X86_BUG_MMIO_STALE_DATA X86_BUG(25) /* "mmio_stale_data" CPU is affected by Processor MMIO Stale Data vulnerabilities */ -#define X86_BUG_MMIO_UNKNOWN X86_BUG(26) /* "mmio_unknown" CPU is too old and its MMIO Stale Data status is unknown */ +/* unused, was #define X86_BUG_MMIO_UNKNOWN X86_BUG(26) * "mmio_unknown" CPU is too old and its MMIO Stale Data status is unknown */ #define X86_BUG_RETBLEED X86_BUG(27) /* "retbleed" CPU is affected by RETBleed */ #define X86_BUG_EIBRS_PBRSB X86_BUG(28) /* "eibrs_pbrsb" EIBRS is vulnerable to Post Barrier RSB Predictions */ #define X86_BUG_SMT_RSB X86_BUG(29) /* "smt_rsb" CPU is vulnerable to Cross-Thread Return Address Predictions */