Skip to content

Commit 7df5488

Browse files
pa1guptasuryasaimadhu
pa1gupta
authored and
suryasaimadhu
committed
x86/bugs: Add "unknown" reporting for MMIO Stale Data
Older Intel CPUs that are not in the affected processor list for MMIO Stale Data vulnerabilities currently report "Not affected" in sysfs, which may not be correct. Vulnerability status for these older CPUs is unknown. Add known-not-affected CPUs to the whitelist. Report "unknown" mitigation status for CPUs that are not in blacklist, whitelist and also don't enumerate MSR ARCH_CAPABILITIES bits that reflect hardware immunity to MMIO Stale Data vulnerabilities. Mitigation is not deployed when the status is unknown. [ bp: Massage, fixup. ] Fixes: 8d50cdf ("x86/speculation/mmio: Add sysfs reporting for Processor MMIO Stale Data") Suggested-by: Andrew Cooper <[email protected]> Suggested-by: Tony Luck <[email protected]> Signed-off-by: Pawan Gupta <[email protected]> Signed-off-by: Borislav Petkov <[email protected]> Cc: [email protected] Link: https://lore.kernel.org/r/a932c154772f2121794a5f2eded1a11013114711.1657846269.git.pawan.kumar.gupta@linux.intel.com
1 parent 5b9f0c4 commit 7df5488

File tree

4 files changed

+56
-19
lines changed

4 files changed

+56
-19
lines changed

‎Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst‎

Lines changed: 14 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -230,6 +230,20 @@ The possible values in this file are:
230230
* - 'Mitigation: Clear CPU buffers'
231231
- The processor is vulnerable and the CPU buffer clearing mitigation is
232232
enabled.
233+
* - 'Unknown: No mitigations'
234+
- The processor vulnerability status is unknown because it is
235+
out of Servicing period. Mitigation is not attempted.
236+
237+
Definitions:
238+
------------
239+
240+
Servicing period: The process of providing functional and security updates to
241+
Intel processors or platforms, utilizing the Intel Platform Update (IPU)
242+
process or other similar mechanisms.
243+
244+
End of Servicing Updates (ESU): ESU is the date at which Intel will no
245+
longer provide Servicing, such as through IPU or other similar update
246+
processes. ESU dates will typically be aligned to end of quarter.
233247

234248
If the processor is vulnerable then the following information is appended to
235249
the above information:

‎arch/x86/include/asm/cpufeatures.h‎

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -457,7 +457,8 @@
457457
#define X86_BUG_ITLB_MULTIHIT X86_BUG(23) /* CPU may incur MCE during certain page attribute changes */
458458
#define X86_BUG_SRBDS X86_BUG(24) /* CPU may leak RNG bits if not mitigated */
459459
#define X86_BUG_MMIO_STALE_DATA X86_BUG(25) /* CPU is affected by Processor MMIO Stale Data vulnerabilities */
460-
#define X86_BUG_RETBLEED X86_BUG(26) /* CPU is affected by RETBleed */
461-
#define X86_BUG_EIBRS_PBRSB X86_BUG(27) /* EIBRS is vulnerable to Post Barrier RSB Predictions */
460+
#define X86_BUG_MMIO_UNKNOWN X86_BUG(26) /* CPU is too old and its MMIO Stale Data status is unknown */
461+
#define X86_BUG_RETBLEED X86_BUG(27) /* CPU is affected by RETBleed */
462+
#define X86_BUG_EIBRS_PBRSB X86_BUG(28) /* EIBRS is vulnerable to Post Barrier RSB Predictions */
462463

463464
#endif /* _ASM_X86_CPUFEATURES_H */

‎arch/x86/kernel/cpu/bugs.c‎

Lines changed: 12 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -433,7 +433,8 @@ static void __init mmio_select_mitigation(void)
433433
u64 ia32_cap;
434434

435435
if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA) ||
436-
cpu_mitigations_off()) {
436+
boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN) ||
437+
cpu_mitigations_off()) {
437438
mmio_mitigation = MMIO_MITIGATION_OFF;
438439
return;
439440
}
@@ -538,6 +539,8 @@ static void __init md_clear_update_mitigation(void)
538539
pr_info("TAA: %s\n", taa_strings[taa_mitigation]);
539540
if (boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
540541
pr_info("MMIO Stale Data: %s\n", mmio_strings[mmio_mitigation]);
542+
else if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN))
543+
pr_info("MMIO Stale Data: Unknown: No mitigations\n");
541544
}
542545

543546
static void __init md_clear_select_mitigation(void)
@@ -2275,6 +2278,9 @@ static ssize_t tsx_async_abort_show_state(char *buf)
22752278

22762279
static ssize_t mmio_stale_data_show_state(char *buf)
22772280
{
2281+
if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN))
2282+
return sysfs_emit(buf, "Unknown: No mitigations\n");
2283+
22782284
if (mmio_mitigation == MMIO_MITIGATION_OFF)
22792285
return sysfs_emit(buf, "%s\n", mmio_strings[mmio_mitigation]);
22802286

@@ -2421,6 +2427,7 @@ static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr
24212427
return srbds_show_state(buf);
24222428

24232429
case X86_BUG_MMIO_STALE_DATA:
2430+
case X86_BUG_MMIO_UNKNOWN:
24242431
return mmio_stale_data_show_state(buf);
24252432

24262433
case X86_BUG_RETBLEED:
@@ -2480,7 +2487,10 @@ ssize_t cpu_show_srbds(struct device *dev, struct device_attribute *attr, char *
24802487

24812488
ssize_t cpu_show_mmio_stale_data(struct device *dev, struct device_attribute *attr, char *buf)
24822489
{
2483-
return cpu_show_common(dev, attr, buf, X86_BUG_MMIO_STALE_DATA);
2490+
if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN))
2491+
return cpu_show_common(dev, attr, buf, X86_BUG_MMIO_UNKNOWN);
2492+
else
2493+
return cpu_show_common(dev, attr, buf, X86_BUG_MMIO_STALE_DATA);
24842494
}
24852495

24862496
ssize_t cpu_show_retbleed(struct device *dev, struct device_attribute *attr, char *buf)

‎arch/x86/kernel/cpu/common.c‎

Lines changed: 27 additions & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -1135,7 +1135,8 @@ static void identify_cpu_without_cpuid(struct cpuinfo_x86 *c)
11351135
#define NO_SWAPGS BIT(6)
11361136
#define NO_ITLB_MULTIHIT BIT(7)
11371137
#define NO_SPECTRE_V2 BIT(8)
1138-
#define NO_EIBRS_PBRSB BIT(9)
1138+
#define NO_MMIO BIT(9)
1139+
#define NO_EIBRS_PBRSB BIT(10)
11391140

11401141
#define VULNWL(vendor, family, model, whitelist) \
11411142
X86_MATCH_VENDOR_FAM_MODEL(vendor, family, model, whitelist)
@@ -1158,6 +1159,11 @@ static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = {
11581159
VULNWL(VORTEX, 6, X86_MODEL_ANY, NO_SPECULATION),
11591160

11601161
/* Intel Family 6 */
1162+
VULNWL_INTEL(TIGERLAKE, NO_MMIO),
1163+
VULNWL_INTEL(TIGERLAKE_L, NO_MMIO),
1164+
VULNWL_INTEL(ALDERLAKE, NO_MMIO),
1165+
VULNWL_INTEL(ALDERLAKE_L, NO_MMIO),
1166+
11611167
VULNWL_INTEL(ATOM_SALTWELL, NO_SPECULATION | NO_ITLB_MULTIHIT),
11621168
VULNWL_INTEL(ATOM_SALTWELL_TABLET, NO_SPECULATION | NO_ITLB_MULTIHIT),
11631169
VULNWL_INTEL(ATOM_SALTWELL_MID, NO_SPECULATION | NO_ITLB_MULTIHIT),
@@ -1176,9 +1182,9 @@ static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = {
11761182
VULNWL_INTEL(ATOM_AIRMONT_MID, NO_L1TF | MSBDS_ONLY | NO_SWAPGS | NO_ITLB_MULTIHIT),
11771183
VULNWL_INTEL(ATOM_AIRMONT_NP, NO_L1TF | NO_SWAPGS | NO_ITLB_MULTIHIT),
11781184

1179-
VULNWL_INTEL(ATOM_GOLDMONT, NO_MDS | NO_L1TF | NO_SWAPGS | NO_ITLB_MULTIHIT),
1180-
VULNWL_INTEL(ATOM_GOLDMONT_D, NO_MDS | NO_L1TF | NO_SWAPGS | NO_ITLB_MULTIHIT),
1181-
VULNWL_INTEL(ATOM_GOLDMONT_PLUS, NO_MDS | NO_L1TF | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_EIBRS_PBRSB),
1185+
VULNWL_INTEL(ATOM_GOLDMONT, NO_MDS | NO_L1TF | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),
1186+
VULNWL_INTEL(ATOM_GOLDMONT_D, NO_MDS | NO_L1TF | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),
1187+
VULNWL_INTEL(ATOM_GOLDMONT_PLUS, NO_MDS | NO_L1TF | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO | NO_EIBRS_PBRSB),
11821188

11831189
/*
11841190
* Technically, swapgs isn't serializing on AMD (despite it previously
@@ -1193,18 +1199,18 @@ static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = {
11931199
VULNWL_INTEL(ATOM_TREMONT_D, NO_ITLB_MULTIHIT | NO_EIBRS_PBRSB),
11941200

11951201
/* AMD Family 0xf - 0x12 */
1196-
VULNWL_AMD(0x0f, NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT),
1197-
VULNWL_AMD(0x10, NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT),
1198-
VULNWL_AMD(0x11, NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT),
1199-
VULNWL_AMD(0x12, NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT),
1202+
VULNWL_AMD(0x0f, NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),
1203+
VULNWL_AMD(0x10, NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),
1204+
VULNWL_AMD(0x11, NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),
1205+
VULNWL_AMD(0x12, NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),
12001206

12011207
/* FAMILY_ANY must be last, otherwise 0x0f - 0x12 matches won't work */
1202-
VULNWL_AMD(X86_FAMILY_ANY, NO_MELTDOWN | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT),
1203-
VULNWL_HYGON(X86_FAMILY_ANY, NO_MELTDOWN | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT),
1208+
VULNWL_AMD(X86_FAMILY_ANY, NO_MELTDOWN | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),
1209+
VULNWL_HYGON(X86_FAMILY_ANY, NO_MELTDOWN | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),
12041210

12051211
/* Zhaoxin Family 7 */
1206-
VULNWL(CENTAUR, 7, X86_MODEL_ANY, NO_SPECTRE_V2 | NO_SWAPGS),
1207-
VULNWL(ZHAOXIN, 7, X86_MODEL_ANY, NO_SPECTRE_V2 | NO_SWAPGS),
1212+
VULNWL(CENTAUR, 7, X86_MODEL_ANY, NO_SPECTRE_V2 | NO_SWAPGS | NO_MMIO),
1213+
VULNWL(ZHAOXIN, 7, X86_MODEL_ANY, NO_SPECTRE_V2 | NO_SWAPGS | NO_MMIO),
12081214
{}
12091215
};
12101216

@@ -1358,10 +1364,16 @@ static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
13581364
* Affected CPU list is generally enough to enumerate the vulnerability,
13591365
* but for virtualization case check for ARCH_CAP MSR bits also, VMM may
13601366
* not want the guest to enumerate the bug.
1367+
*
1368+
* Set X86_BUG_MMIO_UNKNOWN for CPUs that are neither in the blacklist,
1369+
* nor in the whitelist and also don't enumerate MSR ARCH_CAP MMIO bits.
13611370
*/
1362-
if (cpu_matches(cpu_vuln_blacklist, MMIO) &&
1363-
!arch_cap_mmio_immune(ia32_cap))
1364-
setup_force_cpu_bug(X86_BUG_MMIO_STALE_DATA);
1371+
if (!arch_cap_mmio_immune(ia32_cap)) {
1372+
if (cpu_matches(cpu_vuln_blacklist, MMIO))
1373+
setup_force_cpu_bug(X86_BUG_MMIO_STALE_DATA);
1374+
else if (!cpu_matches(cpu_vuln_whitelist, NO_MMIO))
1375+
setup_force_cpu_bug(X86_BUG_MMIO_UNKNOWN);
1376+
}
13651377

13661378
if (!cpu_has(c, X86_FEATURE_BTC_NO)) {
13671379
if (cpu_matches(cpu_vuln_blacklist, RETBLEED) || (ia32_cap & ARCH_CAP_RSBA))

0 commit comments

Comments
 (0)