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x86/bugs: Add ITLB_MULTIHIT bug infrastructure

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Some processors may incur a machine check error possibly resulting in an
unrecoverable CPU lockup when an instruction fetch encounters a TLB
multi-hit in the instruction TLB. This can occur when the page size is
changed along with either the physical address or cache type. The relevant
erratum can be found here:

   https://bugzilla.kernel.org/show_bug.cgi?id=205195

There are other processors affected for which the erratum does not fully
disclose the impact.

This issue affects both bare-metal x86 page tables and EPT.

It can be mitigated by either eliminating the use of large pages or by
using careful TLB invalidations when changing the page size in the page
tables.

Just like Spectre, Meltdown, L1TF and MDS, a new bit has been allocated in
MSR_IA32_ARCH_CAPABILITIES (PSCHANGE_MC_NO) and will be set on CPUs which
are mitigated against this issue.

Signed-off-by: Vineela Tummalapalli <vineela.tummalapalli@intel.com>
Co-developed-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Vineela Tummalapalli
2019-11-04 12:22:01 +01:00
committed by Thomas Gleixner
parent ca8888d7ae
commit db4d30fbb7
7 changed files with 66 additions and 29 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
arch/x86/kernel/cpu/bugs.c
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@@ -1419,6 +1419,11 @@ static ssize_t l1tf_show_state(char *buf)
}
#endif
static ssize_t itlb_multihit_show_state(char *buf)
{
return sprintf(buf, "Processor vulnerable\n");
}
static ssize_t mds_show_state(char *buf)
{
if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
@@ -1524,6 +1529,9 @@ static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr
case X86_BUG_TAA:
return tsx_async_abort_show_state(buf);
case X86_BUG_ITLB_MULTIHIT:
return itlb_multihit_show_state(buf);
default:
break;
}
@@ -1565,4 +1573,9 @@ ssize_t cpu_show_tsx_async_abort(struct device *dev, struct device_attribute *at
{
return cpu_show_common(dev, attr, buf, X86_BUG_TAA);
}
ssize_t cpu_show_itlb_multihit(struct device *dev, struct device_attribute *attr, char *buf)
{
return cpu_show_common(dev, attr, buf, X86_BUG_ITLB_MULTIHIT);
}
#endif