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x86/bugs: Add "unknown" reporting for MMIO Stale Data

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commit 7df548840c496b0141fb2404b889c346380c2b22 upstream.

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: 8d50cdf8b834 ("x86/speculation/mmio: Add sysfs reporting for Processor MMIO Stale Data")
Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Suggested-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/a932c154772f2121794a5f2eded1a11013114711.1657846269.git.pawan.kumar.gupta@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Pawan Gupta
2022-08-03 14:41:32 -07:00
committed by Greg Kroah-Hartman
parent e3e0d11729
commit 14cbbb9c99
4 changed files with 56 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
arch/x86/kernel/cpu/bugs.c
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@@ -424,7 +424,8 @@ 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;
}
@@ -529,6 +530,8 @@ 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");
}
static void __init md_clear_select_mitigation(void)
@@ -2198,6 +2201,9 @@ 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: No mitigations\n");
if (mmio_mitigation == MMIO_MITIGATION_OFF)
return sysfs_emit(buf, "%s\n", mmio_strings[mmio_mitigation]);
@@ -2344,6 +2350,7 @@ 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:
@@ -2403,7 +2410,10 @@ 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)