From 57e025916cd91551791d99f73fb8de56495077c6 Mon Sep 17 00:00:00 2001
From: mlarkin <mlarkin@openbsd.org>
Date: Sat, 23 Jul 2016 07:25:29 +0000
Subject: [PATCH] Fix a few CPUID emulation issues:

Don't advertise a hyperthreaded CPU. This doesn't make a lot of sense now
as we only provide UP guest support. This, combined with the other CPUID
issues fixed, fooled NetBSD's topology enumeration code into thinking we
had an unsupportable core/thread/package configuration.

Also fixed the unsupported CPUID functions by returning 0 in the return
registers instead of leaving whatever trash happened to be there before
the call was made.
---
 sys/arch/amd64/amd64/vmm.c | 49 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 47 insertions(+), 2 deletions(-)

diff --git a/sys/arch/amd64/amd64/vmm.c b/sys/arch/amd64/amd64/vmm.c
index bb19cb1f2fe..082547524ae 100644
--- a/sys/arch/amd64/amd64/vmm.c
+++ b/sys/arch/amd64/amd64/vmm.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: vmm.c,v 1.70 2016/07/23 07:17:21 mlarkin Exp $	*/
+/*	$OpenBSD: vmm.c,v 1.71 2016/07/23 07:25:29 mlarkin Exp $	*/
 /*
  * Copyright (c) 2014 Mike Larkin <mlarkin@openbsd.org>
  *
@@ -3381,6 +3381,7 @@ vmx_handle_cpuid(struct vcpu *vcpu)
 		 *  XXX - timestamp (CPUID_TSC)
 		 *  monitor/mwait (CPUIDECX_MWAIT)
 		 *  performance monitoring (CPUIDECX_PDCM)
+		 *  hyperthreading (CPUID_HTT)
 		 * plus:
 		 *  hypervisor (CPUIDECX_HV)
 		 */
@@ -3389,11 +3390,15 @@ vmx_handle_cpuid(struct vcpu *vcpu)
 		    CPUIDECX_MWAIT | CPUIDECX_PDCM |
 		    CPUIDECX_VMX | CPUIDECX_XSAVE);
 		*rdx = curcpu()->ci_feature_flags &
-		    ~(CPUID_ACPI | CPUID_TM | CPUID_TSC);
+		    ~(CPUID_ACPI | CPUID_TM | CPUID_TSC | CPUID_HTT);
 		break;
 	case 0x02:	/* Cache and TLB information */
 		DPRINTF("vmx_handle_cpuid: function 0x02 (cache/TLB) not"
 		    " supported\n");
+		*rax = 0;
+		*rbx = 0;
+		*rcx = 0;
+		*rdx = 0;
 		break;
 	case 0x03:	/* Processor serial number (not supported) */
 		*rax = 0;
@@ -3404,6 +3409,10 @@ vmx_handle_cpuid(struct vcpu *vcpu)
 	case 0x04:
 		DPRINTF("vmx_handle_cpuid: function 0x04 (deterministic "
 		    "cache info) not supported\n");
+		*rax = 0;
+		*rbx = 0;
+		*rcx = 0;
+		*rdx = 0;
 		break;
 	case 0x05:	/* MONITOR/MWAIT (not supported) */
 		*rax = 0;
@@ -3435,6 +3444,10 @@ vmx_handle_cpuid(struct vcpu *vcpu)
 	case 0x09:	/* Direct Cache Access (not supported) */
 		DPRINTF("vmx_handle_cpuid: function 0x09 (direct cache access)"
 		    " not supported\n");
+		*rax = 0;
+		*rbx = 0;
+		*rcx = 0;
+		*rdx = 0;
 		break;
 	case 0x0a:	/* Architectural performance monitoring */
 		*rax = 0;
@@ -3445,26 +3458,50 @@ vmx_handle_cpuid(struct vcpu *vcpu)
 	case 0x0b:	/* Extended topology enumeration (not supported) */
 		DPRINTF("vmx_handle_cpuid: function 0x0b (topology enumeration)"
 		    " not supported\n");
+		*rax = 0;
+		*rbx = 0;
+		*rcx = 0;
+		*rdx = 0;
 		break;
 	case 0x0d:	/* Processor ext. state information (not supported) */
 		DPRINTF("vmx_handle_cpuid: function 0x0d (ext. state info)"
 		    " not supported\n");
+		*rax = 0;
+		*rbx = 0;
+		*rcx = 0;
+		*rdx = 0;
 		break;
 	case 0x0f:	/* QoS info (not supported) */
 		DPRINTF("vmx_handle_cpuid: function 0x0f (QoS info)"
 		    " not supported\n");
+		*rax = 0;
+		*rbx = 0;
+		*rcx = 0;
+		*rdx = 0;
 		break;
 	case 0x14:	/* Processor Trace info (not supported) */
 		DPRINTF("vmx_handle_cpuid: function 0x14 (processor trace info)"
 		    " not supported\n");
+		*rax = 0;
+		*rbx = 0;
+		*rcx = 0;
+		*rdx = 0;
 		break;
 	case 0x15:	/* TSC / Core Crystal Clock info (not supported) */
 		DPRINTF("vmx_handle_cpuid: function 0x15 (TSC / CCC info)"
 		    " not supported\n");
+		*rax = 0;
+		*rbx = 0;
+		*rcx = 0;
+		*rdx = 0;
 		break;
 	case 0x16:	/* Processor frequency info (not supported) */
 		DPRINTF("vmx_handle_cpuid: function 0x16 (frequency info)"
 		    " not supported\n");
+		*rax = 0;
+		*rbx = 0;
+		*rcx = 0;
+		*rdx = 0;
 		break;
 	case 0x40000000:	/* Hypervisor information */
 		*rax = 0;
@@ -3522,9 +3559,17 @@ vmx_handle_cpuid(struct vcpu *vcpu)
 	case 0x80000008:	/* Phys bits info and topology (AMD) */
 		DPRINTF("vmx_handle_cpuid: function 0x80000008 (phys bits info)"
 		    " not supported\n");
+		*rax = 0;
+		*rbx = 0;
+		*rcx = 0;
+		*rdx = 0;
 		break;
 	default:
 		DPRINTF("vmx_handle_cpuid: unsupported rax=0x%llx\n", *rax);
+		*rax = 0;
+		*rbx = 0;
+		*rcx = 0;
+		*rdx = 0;
 	}
 
 	vcpu->vc_gueststate.vg_rip += insn_length;
-- 
2.20.1