linux-kernel - [PATCH v3 05/18] x86/reboot: Disable virtualization during reboot iff callback is registered

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20230512235026.808058-6-seanjc@google.com>
Date:   Fri, 12 May 2023 16:50:13 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Kai Huang <kai.huang@...el.com>, Chao Gao <chao.gao@...el.com>
Subject: [PATCH v3 05/18] x86/reboot: Disable virtualization during reboot iff
 callback is registered

Attempt to disable virtualization during an emergency reboot if and only
if there is a registered virt callback, i.e. iff a hypervisor (KVM) is
active.  If there's no active hypervisor, then the CPU can't be operating
with VMX or SVM enabled (barring an egregious bug).

Note, IRQs are disabled, which prevents KVM from coming along and enabling
virtualization after the fact.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kernel/reboot.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 92b380e199a3..20f7bdabc52e 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -22,7 +22,6 @@
 #include <asm/reboot_fixups.h>
 #include <asm/reboot.h>
 #include <asm/pci_x86.h>
-#include <asm/virtext.h>
 #include <asm/cpu.h>
 #include <asm/nmi.h>
 #include <asm/smp.h>
@@ -545,7 +544,7 @@ static void emergency_reboot_disable_virtualization(void)
 	 * Do the NMI shootdown even if virtualization is off on _this_ CPU, as
 	 * other CPUs may have virtualization enabled.
 	 */
-	if (cpu_has_vmx() || cpu_has_svm(NULL)) {
+	if (rcu_access_pointer(cpu_emergency_virt_callback)) {
 		/* Safely force _this_ CPU out of VMX/SVM operation. */
 		cpu_emergency_disable_virtualization();
 
-- 
2.40.1.606.ga4b1b128d6-goog