From 77ffa26374370c1c9805f9596f37a44d412a7fdb Mon Sep 17 00:00:00 2001 From: Andrew Cooper Date: Wed, 23 Jul 2014 18:08:47 +0200 Subject: [PATCH] x86/kexec: fix kexec on systems which boot in x2apic mode Moving straight from fully disabled to x2apic mode is an illegal state transition, and causes an unconditional #GP fault. Bounce through xapic mode to avoid the fault. In addition, avoid bouncing through the various apic modes if the mode is already correct. Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich --- xen/arch/x86/apic.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/xen/arch/x86/apic.c b/xen/arch/x86/apic.c index 0e5e302ec1..bbcc0a16d0 100644 --- a/xen/arch/x86/apic.c +++ b/xen/arch/x86/apic.c @@ -314,7 +314,7 @@ void disable_local_APIC(void) ~(MSR_IA32_APICBASE_ENABLE|MSR_IA32_APICBASE_EXTD)); } - if ( kexecing ) + if ( kexecing && (current_local_apic_mode() != apic_boot_mode) ) { uint64_t msr_content; rdmsrl(MSR_IA32_APICBASE, msr_content); @@ -330,7 +330,9 @@ void disable_local_APIC(void) wrmsrl(MSR_IA32_APICBASE, msr_content); break; case APIC_MODE_X2APIC: - msr_content |= (MSR_IA32_APICBASE_ENABLE|MSR_IA32_APICBASE_EXTD); + msr_content |= MSR_IA32_APICBASE_ENABLE; + wrmsrl(MSR_IA32_APICBASE, msr_content); + msr_content |= MSR_IA32_APICBASE_EXTD; wrmsrl(MSR_IA32_APICBASE, msr_content); break; default: -- 2.30.2