Re: [RESEND RFC PATCH] x86/bugs: Add "unknown" reporting for MMIO Stale Data
From: Borislav Petkov
Date: Fri Jul 29 2022 - 10:05:48 EST
On Thu, Jul 28, 2022 at 07:28:51PM -0700, Pawan Gupta wrote:
> To keep things simple, can this stay in cpu/common.c?
I know, right?
The gullible maintainer should simply take your half-baked patch so that
you can check off that box and then he can clean it up later.
So you've been doing this kernel development thing for a while. Didn't
it get obvious by now that we don't do half-baked?!
See if this works:
---
diff --git a/Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst b/Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
index 9393c50b5afc..14cd3c6ddec6 100644
--- a/Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
+++ b/Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
@@ -230,6 +230,21 @@ The possible values in this file are:
* - 'Mitigation: Clear CPU buffers'
- The processor is vulnerable and the CPU buffer clearing mitigation is
enabled.
+ * - 'Unknown: CPU is beyond its servicing period'
+ - The processor vulnerability status is unknown because it is
+ out of Servicing period. Mitigation is not attempted.
+
+
+Definitions:
+------------
+
+Servicing period: The process of providing functional and security
+updates to Intel processors or platforms, utilizing the Intel Platform
+Update (IPU) process or other similar mechanisms.
+
+End of Servicing Updates (ESU): ESU is the date at which Intel will no
+longer provide Servicing, such as through IPU or other similar update
+processes. ESU dates will typically be aligned to end of quarter.
If the processor is vulnerable then the following information is appended to
the above information:
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index ea34cc31b047..fe66e94d7b86 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -154,6 +154,7 @@ extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit);
} while (0)
#define setup_force_cpu_bug(bit) setup_force_cpu_cap(bit)
+#define setup_clear_cpu_bug(bit) setup_clear_cpu_cap(bit)
#if defined(__clang__) && !defined(CONFIG_CC_HAS_ASM_GOTO)
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 5fe7f6c8a7a4..130cb46ecaf9 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -454,7 +454,8 @@
#define X86_BUG_TAA X86_BUG(22) /* CPU is affected by TSX Async Abort(TAA) */
#define X86_BUG_ITLB_MULTIHIT X86_BUG(23) /* CPU may incur MCE during certain page attribute changes */
#define X86_BUG_SRBDS X86_BUG(24) /* CPU may leak RNG bits if not mitigated */
-#define X86_BUG_MMIO_STALE_DATA X86_BUG(25) /* CPU is affected by Processor MMIO Stale Data vulnerabilities */
-#define X86_BUG_RETBLEED X86_BUG(26) /* CPU is affected by RETBleed */
+#define X86_BUG_MMIO_UNKNOWN X86_BUG(25) /* CPU is too old and its MMIO Stale Data status is unknown */
+#define X86_BUG_MMIO_STALE_DATA X86_BUG(26) /* CPU is affected by Processor MMIO Stale Data vulnerabilities */
+#define X86_BUG_RETBLEED X86_BUG(27) /* CPU is affected by RETBleed */
#endif /* _ASM_X86_CPUFEATURES_H */
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 6454bc767f0f..a83d1c4265ae 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -433,7 +433,8 @@ static void __init mmio_select_mitigation(void)
u64 ia32_cap;
if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA) ||
- cpu_mitigations_off()) {
+ boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN) ||
+ cpu_mitigations_off()) {
mmio_mitigation = MMIO_MITIGATION_OFF;
return;
}
@@ -2247,6 +2248,9 @@ 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: CPU is beyond its servicing period\n");
+
if (mmio_mitigation == MMIO_MITIGATION_OFF)
return sysfs_emit(buf, "%s\n", mmio_strings[mmio_mitigation]);
@@ -2378,6 +2382,7 @@ 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:
@@ -2437,7 +2442,10 @@ 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)
{
- return cpu_show_common(dev, attr, buf, X86_BUG_MMIO_STALE_DATA);
+ 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);
}
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 736262a76a12..fb3e8576a3b4 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1356,9 +1356,13 @@ static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
* but for virtualization case check for ARCH_CAP MSR bits also, VMM may
* not want the guest to enumerate the bug.
*/
- if (cpu_matches(cpu_vuln_blacklist, MMIO) &&
- !arch_cap_mmio_immune(ia32_cap))
- setup_force_cpu_bug(X86_BUG_MMIO_STALE_DATA);
+ if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN)) {
+ if (cpu_matches(cpu_vuln_blacklist, MMIO) &&
+ !arch_cap_mmio_immune(ia32_cap)) {
+ setup_clear_cpu_bug(X86_BUG_MMIO_UNKNOWN);
+ setup_force_cpu_bug(X86_BUG_MMIO_STALE_DATA);
+ }
+ }
if (!cpu_has(c, X86_FEATURE_BTC_NO)) {
if (cpu_matches(cpu_vuln_blacklist, RETBLEED) || (ia32_cap & ARCH_CAP_RSBA))
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 663f6e6dd288..5b2508adc38a 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -372,6 +372,10 @@ static void early_init_intel(struct cpuinfo_x86 *c)
static void bsp_init_intel(struct cpuinfo_x86 *c)
{
resctrl_cpu_detect(c);
+
+ /* Set on older crap */
+ if (c->x86_model < INTEL_FAM6_IVYBRIDGE)
+ setup_force_cpu_bug(X86_BUG_MMIO_UNKNOWN);
}
#ifdef CONFIG_X86_32
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette