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[v4,07/13] pc: apic_common: reset APIC ID to initial ID when switching into x2APIC mode

Message ID 1476878743-144953-8-git-send-email-imammedo@redhat.com
State New
Headers show

Commit Message

Igor Mammedov Oct. 19, 2016, 12:05 p.m. UTC 
SDM: x2APIC State Transitions:
         State Changes From xAPIC Mode to x2APIC Mode
"
Any APIC ID value written to the memory-mapped
local APIC ID register is not preserved
"

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
---
 hw/intc/apic_common.c | 5 +++++
 1 file changed, 5 insertions(+)

Comments

Eduardo Habkost Oct. 19, 2016, 12:56 p.m. UTC | #1 
On Wed, Oct 19, 2016 at 02:05:37PM +0200, Igor Mammedov wrote:
> SDM: x2APIC State Transitions:
>          State Changes From xAPIC Mode to x2APIC Mode
> "
> Any APIC ID value written to the memory-mapped
> local APIC ID register is not preserved
> "
> 
> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>

Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
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Patch

diff --git a/hw/intc/apic_common.c b/hw/intc/apic_common.c
index ea3c8ca..d78c885 100644
--- a/hw/intc/apic_common.c
+++ b/hw/intc/apic_common.c
@@ -40,6 +40,11 @@  void cpu_set_apic_base(DeviceState *dev, uint64_t val)
     if (dev) {
         APICCommonState *s = APIC_COMMON(dev);
         APICCommonClass *info = APIC_COMMON_GET_CLASS(s);
+        /* switching to x2APIC, reset possibly modified xAPIC ID */
+        if (!(s->apicbase & MSR_IA32_APICBASE_EXTD) &&
+            (val & MSR_IA32_APICBASE_EXTD)) {
+            s->id = s->initial_apic_id;
+        }
         info->set_base(s, val);
     }
 }