From: Thomas Gleixner <tglx@linutronix.de>
Subject: KVM: SVM: Move spec control call after restore of GS
Patch-mainline: v4.17-rc7
Git-commit: 15e6c22fd8e5a42c5ed6d487b7c9fe44c2517765
References: bsc#1087082 CVE-2018-3639
svm_vcpu_run() invokes x86_spec_ctrl_restore_host() after VMEXIT, but
before the host GS is restored. x86_spec_ctrl_restore_host() uses 'current'
to determine the host SSBD state of the thread. 'current' is GS based, but
host GS is not yet restored and the access causes a triple fault.
Move the call after the host GS restore.
Fixes: 5cf687548705 ("x86/bugs, KVM: Support the combination of guest and host IBRS")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Joerg Roedel <jroedel@suse.de>
---
arch/x86/kvm/svm.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -5449,6 +5449,18 @@ static void svm_vcpu_run(struct kvm_vcpu
#endif
);
+ /* Eliminate branch target predictions from guest mode */
+ vmexit_fill_RSB();
+
+#ifdef CONFIG_X86_64
+ wrmsrl(MSR_GS_BASE, svm->host.gs_base);
+#else
+ loadsegment(fs, svm->host.fs);
+#ifndef CONFIG_X86_32_LAZY_GS
+ loadsegment(gs, svm->host.gs);
+#endif
+#endif
+
/*
* We do not use IBRS in the kernel. If this vCPU has used the
* SPEC_CTRL MSR it may have left it on; save the value and
@@ -5469,18 +5481,6 @@ static void svm_vcpu_run(struct kvm_vcpu
x86_spec_ctrl_restore_host(svm->spec_ctrl);
- /* Eliminate branch target predictions from guest mode */
- vmexit_fill_RSB();
-
-#ifdef CONFIG_X86_64
- wrmsrl(MSR_GS_BASE, svm->host.gs_base);
-#else
- loadsegment(fs, svm->host.fs);
-#ifndef CONFIG_X86_32_LAZY_GS
- loadsegment(gs, svm->host.gs);
-#endif
-#endif
-
reload_tss(vcpu);
local_irq_disable();