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[Xen-devel] [PATCH] hvm: Fix APIC-ID cpuid intercept

To: Keir.Fraser@xxxxxxxxxxxx
Subject: [Xen-devel] [PATCH] hvm: Fix APIC-ID cpuid intercept
From: "Andre Przywara" <andre.przywara@xxxxxxx>
Date: Wed, 06 Feb 2008 23:44:54 +0100
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the HVM CPUID intercept does not mask out the local APIC ID bits in CPUID Fn0000_0001, bits 24-31 in EBX. This results in inconsistent values of subsequent calls to cpuid on the same VCPU (delivering the value of the physical CPU), depending on the current scheduling. This for instance confuses Linux' NUMA code. The attached patch fixes this by replacing the physical APIC ID with the VCPU number, both in the VMX and SVM branches.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>

I hope this does not trigger any side effects...


Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 277-84917
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diff -r f8db1c6baad9 xen/arch/x86/hvm/svm/svm.c
--- a/xen/arch/x86/hvm/svm/svm.c        Tue Feb 05 23:27:12 2008 +0000
+++ b/xen/arch/x86/hvm/svm/svm.c        Wed Feb 06 13:36:50 2008 +0100
@@ -1015,6 +1015,8 @@ static void svm_vmexit_do_cpuid(struct v
         __clear_bit(X86_FEATURE_HT & 31, &edx);
         ebx &= 0xFF00FFFF;  /* clear the logical processor count when HTT=0 */
         ebx |= 0x00010000;  /* set to 1 just for precaution */
+        ebx &= 0x00FFFFFF;  /* clear the APIC ID */
+        ebx |= (current->vcpu_id&0xFF)<<24;   /* replace with vcpu_id */
     case 0x80000001:
diff -r f8db1c6baad9 xen/arch/x86/hvm/vmx/vmx.c
--- a/xen/arch/x86/hvm/vmx/vmx.c        Tue Feb 05 23:27:12 2008 +0000
+++ b/xen/arch/x86/hvm/vmx/vmx.c        Wed Feb 06 13:36:50 2008 +0100
@@ -1311,6 +1311,8 @@ void vmx_cpuid_intercept(
     case 0x00000001:
         *ecx &= ~VMX_VCPU_CPUID_L1_ECX_RESERVED;
         *ebx &= NUM_THREADS_RESET_MASK;
+        *ebx &= 0x00FFFFFF;
+        *ebx |= (current->vcpu_id&0xFF)<<24;
         *ecx &= ~(bitmaskof(X86_FEATURE_VMXE) |
                   bitmaskof(X86_FEATURE_EST)  |
                   bitmaskof(X86_FEATURE_TM2)  |

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