44 lines
1.4 KiB
Diff
44 lines
1.4 KiB
Diff
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# HG changeset patch
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# User Keir Fraser <keir@xen.org>
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# Date 1291116848 0
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# Node ID 8420b82c22c2cad54860ffdbe8bcec21c65c86be
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# Parent d281061e6ec06bbbf8e2b0fadbeb9d1a04bc32e2
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x86 hvm: Do not overwrite boot-cpu capability data on VMX/SVM startup.
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Apparently required back in the earliest days of Xen, we now properly
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initialise CPU capabilities early during bootstrap. Re-writing
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capability data later now causes problems if specific features have
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been deliberately masked out.
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Thanks to Weidong Han at Intel for finding such a bug where XSAVE
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feature is masked out by default, but then erroneously written back
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during VMX initialisation. This would cause memory corruption problems
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during boot for XSAVE-capable systems.
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Signed-off-by: Keir Fraser <keir@xen.org>
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--- a/xen/arch/x86/hvm/svm/svm.c
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+++ b/xen/arch/x86/hvm/svm/svm.c
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@@ -915,9 +915,6 @@ void start_svm(struct cpuinfo_x86 *c)
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return;
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}
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- /* Xen does not fill x86_capability words except 0. */
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- boot_cpu_data.x86_capability[5] = cpuid_ecx(0x80000001);
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-
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if ( !test_bit(X86_FEATURE_SVME, &boot_cpu_data.x86_capability) )
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return;
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--- a/xen/arch/x86/hvm/vmx/vmx.c
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+++ b/xen/arch/x86/hvm/vmx/vmx.c
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@@ -1433,9 +1433,6 @@ void start_vmx(void)
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return;
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}
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- /* Xen does not fill x86_capability words except 0. */
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- boot_cpu_data.x86_capability[4] = cpuid_ecx(1);
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-
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if ( !test_bit(X86_FEATURE_VMXE, &boot_cpu_data.x86_capability) )
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return;
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