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[PATCH v2] kvm: x86: zero EFER on INIT

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  [PATCH v2] kvm: x86: zero EFER on INIT Paolo Bonzini <pbonzini@redhat.com> - 2015-10-19 11:40 +0200
    Re: [PATCH v2] kvm: x86: zero EFER on INIT Radim Krčmář <rkrcmar@redhat.com> - 2015-10-19 16:50 +0200

#1250506 — [PATCH v2] kvm: x86: zero EFER on INIT

Not zeroing EFER means that a 32-bit firmware cannot enter paging mode
without clearing EFER.LME first (which it should not know about).
Yang Zhang from Intel confirmed that the manual is wrong and EFER is
cleared to zero on INIT.

Fixes: d28bc9dd25ce023270d2e039e7c98d38ecbf7758
Cc: stable@vger.kernel.org
Cc: Yang Z Zhang <yang.z.zhang@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/svm.c | 11 +++++------
 arch/x86/kvm/vmx.c |  3 +--
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index cd8659cfc632..f2c8e4917688 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1089,7 +1089,7 @@ static u64 svm_compute_tsc_offset(struct kvm_vcpu *vcpu, u64 target_tsc)
 	return target_tsc - tsc;
 }
 
-static void init_vmcb(struct vcpu_svm *svm, bool init_event)
+static void init_vmcb(struct vcpu_svm *svm)
 {
 	struct vmcb_control_area *control = &svm->vmcb->control;
 	struct vmcb_save_area *save = &svm->vmcb->save;
@@ -1160,8 +1160,7 @@ static void init_vmcb(struct vcpu_svm *svm, bool init_event)
 	init_sys_seg(&save->ldtr, SEG_TYPE_LDT);
 	init_sys_seg(&save->tr, SEG_TYPE_BUSY_TSS16);
 
-	if (!init_event)
-		svm_set_efer(&svm->vcpu, 0);
+	svm_set_efer(&svm->vcpu, 0);
 	save->dr6 = 0xffff0ff0;
 	kvm_set_rflags(&svm->vcpu, 2);
 	save->rip = 0x0000fff0;
@@ -1215,7 +1214,7 @@ static void svm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 		if (kvm_vcpu_is_reset_bsp(&svm->vcpu))
 			svm->vcpu.arch.apic_base |= MSR_IA32_APICBASE_BSP;
 	}
-	init_vmcb(svm, init_event);
+	init_vmcb(svm);
 
 	kvm_cpuid(vcpu, &eax, &dummy, &dummy, &dummy);
 	kvm_register_write(vcpu, VCPU_REGS_RDX, eax);
@@ -1271,7 +1270,7 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)
 	clear_page(svm->vmcb);
 	svm->vmcb_pa = page_to_pfn(page) << PAGE_SHIFT;
 	svm->asid_generation = 0;
-	init_vmcb(svm, false);
+	init_vmcb(svm);
 
 	svm_init_osvw(&svm->vcpu);
 
@@ -1893,7 +1892,7 @@ static int shutdown_interception(struct vcpu_svm *svm)
 	 * so reinitialize it.
 	 */
 	clear_page(svm->vmcb);
-	init_vmcb(svm, false);
+	init_vmcb(svm);
 
 	kvm_run->exit_reason = KVM_EXIT_SHUTDOWN;
 	return 0;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 15bff51d492a..4d0aa31a42ba 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4932,8 +4932,7 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 	vmx_set_cr0(vcpu, cr0); /* enter rmode */
 	vmx->vcpu.arch.cr0 = cr0;
 	vmx_set_cr4(vcpu, 0);
-	if (!init_event)
-		vmx_set_efer(vcpu, 0);
+	vmx_set_efer(vcpu, 0);
 	vmx_fpu_activate(vcpu);
 	update_exception_bitmap(vcpu);
 
-- 
1.8.3.1

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#1250762

2015-10-19 11:35+0200, Paolo Bonzini:
> Not zeroing EFER means that a 32-bit firmware cannot enter paging mode
> without clearing EFER.LME first (which it should not know about).
> Yang Zhang from Intel confirmed that the manual is wrong and EFER is
> cleared to zero on INIT.

Also in APM v2, "Table 14-1. Initial Processor State.".

> 
> Fixes: d28bc9dd25ce023270d2e039e7c98d38ecbf7758
> Cc: stable@vger.kernel.org
> Cc: Yang Z Zhang <yang.z.zhang@intel.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---

Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
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