[PATCH v2] x86/bugs/multihit: Fix mitigation reporting when VMX is not in use
From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Date: 2020-07-16 19:29:58
Also in:
kvm, lkml
Subsystem:
documentation, the rest, x86 architecture (32-bit and 64-bit), x86 hardware vulnerabilities · Maintainers:
Jonathan Corbet, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Peter Zijlstra, Josh Poimboeuf
On systems that have virtualization disabled or unsupported, sysfs
mitigation for X86_BUG_ITLB_MULTIHIT is reported incorrectly as:
$ cat /sys/devices/system/cpu/vulnerabilities/itlb_multihit
KVM: Vulnerable
System is not vulnerable to DoS attack from a rogue guest when
virtualization is disabled or unsupported in the hardware. Change the
mitigation reporting for these cases.
Fixes: b8e8c8303ff2 ("kvm: mmu: ITLB_MULTIHIT mitigation")
Reported-by: Nelson Dsouza <redacted>
Co-developed-by: Sean Christopherson <redacted>
Signed-off-by: Sean Christopherson <redacted>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
---
v2:
- Change mitigation reporting as per the state on VMX feature.
v1: https://lore.kernel.org/lkml/267631f4db4fd7e9f7ca789c2efaeab44103f68e.1594689154.git.pawan.kumar.gupta@linux.intel.com/ (local)
Documentation/admin-guide/hw-vuln/multihit.rst | 4 ++++
arch/x86/kernel/cpu/bugs.c | 8 +++++++-
2 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/hw-vuln/multihit.rst b/Documentation/admin-guide/hw-vuln/multihit.rst
index ba9988d8bce5..140e4cec38c3 100644
--- a/Documentation/admin-guide/hw-vuln/multihit.rst
+++ b/Documentation/admin-guide/hw-vuln/multihit.rst@@ -80,6 +80,10 @@ The possible values in this file are: - The processor is not vulnerable. * - KVM: Mitigation: Split huge pages - Software changes mitigate this issue. + * - KVM: Mitigation: VMX unsupported + - KVM is not vulnerable because Virtual Machine Extensions (VMX) is not supported. + * - KVM: Mitigation: VMX disabled + - KVM is not vulnerable because Virtual Machine Extensions (VMX) is disabled. * - KVM: Vulnerable - The processor is vulnerable, but no mitigation enabled
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 0b71970d2d3d..b0802d45abd3 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c@@ -31,6 +31,7 @@ #include <asm/intel-family.h> #include <asm/e820/api.h> #include <asm/hypervisor.h> +#include <asm/tlbflush.h> #include "cpu.h"
@@ -1556,7 +1557,12 @@ static ssize_t l1tf_show_state(char *buf) static ssize_t itlb_multihit_show_state(char *buf) { - if (itlb_multihit_kvm_mitigation) + if (!boot_cpu_has(X86_FEATURE_MSR_IA32_FEAT_CTL) || + !boot_cpu_has(X86_FEATURE_VMX)) + return sprintf(buf, "KVM: Mitigation: VMX unsupported\n"); + else if (!(cr4_read_shadow() & X86_CR4_VMXE)) + return sprintf(buf, "KVM: Mitigation: VMX disabled\n"); + else if (itlb_multihit_kvm_mitigation) return sprintf(buf, "KVM: Mitigation: Split huge pages\n"); else return sprintf(buf, "KVM: Vulnerable\n");
--
2.21.3