From: Pawan Gupta pawan.kumar.gupta@linux.intel.com
[ Upstream commit f29dfa53cc8ae6ad93bae619bcc0bf45cab344f7 ]
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 nelson.dsouza@linux.intel.com Co-developed-by: Sean Christopherson sean.j.christopherson@intel.com Signed-off-by: Sean Christopherson sean.j.christopherson@intel.com Signed-off-by: Pawan Gupta pawan.kumar.gupta@linux.intel.com Signed-off-by: Ingo Molnar mingo@kernel.org Reviewed-by: Tony Luck tony.luck@intel.com Acked-by: Thomas Gleixner tglx@linutronix.de Link: https://lore.kernel.org/r/0ba029932a816179b9d14a30db38f0f11ef1f166.159492578... Signed-off-by: Sasha Levin sashal@kernel.org --- 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 ba9988d8bce50..140e4cec38c33 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 b53dcff21438c..8c963ea39f9df 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");