4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Thomas Gleixner <t...@linutronix.de>
commit 15e6c22fd8e5a42c5ed6d487b7c9fe44c2517765 upstream
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: 885f82bfbc6f x86/process: Allow runtime control of Speculative Store
Bypass
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Reviewed-by: Borislav Petkov <b...@suse.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
Acked-by: Paolo Bonzini <pbonz...@redhat.com>
Signed-off-by: David Woodhouse <d...@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
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
@@ -5011,6 +5011,18 @@ 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
@@ -5031,18 +5043,6 @@ 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();
