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-rw-r--r--common/recipes-kernel/linux/linux-yocto-4.9.21/0062-KVM-SVM-Move-spec-control-call-after-restore-of-GS.patch70
1 files changed, 70 insertions, 0 deletions
diff --git a/common/recipes-kernel/linux/linux-yocto-4.9.21/0062-KVM-SVM-Move-spec-control-call-after-restore-of-GS.patch b/common/recipes-kernel/linux/linux-yocto-4.9.21/0062-KVM-SVM-Move-spec-control-call-after-restore-of-GS.patch
new file mode 100644
index 00000000..75caec43
--- /dev/null
+++ b/common/recipes-kernel/linux/linux-yocto-4.9.21/0062-KVM-SVM-Move-spec-control-call-after-restore-of-GS.patch
@@ -0,0 +1,70 @@
+From 21d2555ad333e693fc6859bff2a60b9b24de8d99 Mon Sep 17 00:00:00 2001
+From: Thomas Gleixner <tglx@linutronix.de>
+Date: Fri, 11 May 2018 15:21:01 +0200
+Subject: [PATCH 62/93] KVM: SVM: Move spec control call after restore of GS
+
+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 <tglx@linutronix.de>
+Reviewed-by: Borislav Petkov <bp@suse.de>
+Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
+Acked-by: Paolo Bonzini <pbonzini@redhat.com>
+Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ arch/x86/kvm/svm.c | 24 ++++++++++++------------
+ 1 file changed, 12 insertions(+), 12 deletions(-)
+
+diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
+index 47779f5..9991462 100644
+--- a/arch/x86/kvm/svm.c
++++ b/arch/x86/kvm/svm.c
+@@ -4999,6 +4999,18 @@ static void svm_vcpu_run(struct kvm_vcpu *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
+@@ -5019,18 +5031,6 @@ static void svm_vcpu_run(struct kvm_vcpu *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();
+--
+2.7.4
+