Re: [Xen-devel] [PATCH v2 4/4] x86/apic: allow enabling x2APIC mode regardless of interrupt remapping

[Jan Beulich <jbeulich@xxxxxxxx>]

On 04.12.2019 14:51, Roger Pau Monné wrote:
> On Tue, Dec 03, 2019 at 04:33:09PM +0100, Jan Beulich wrote:
>> On 29.11.2019 12:28, Roger Pau Monne wrote:
>>> --- a/xen/arch/x86/apic.c
>>> +++ b/xen/arch/x86/apic.c
>>> @@ -492,7 +492,8 @@ static void __enable_x2apic(void)
>>>  
>>>  static void resume_x2apic(void)
>>>  {
>>> -    iommu_enable_x2apic();
>>> +    if ( iommu_supports_x2apic() )
>>> +        iommu_enable_x2apic();
>>
>> The hooks called by this function are __init, and at least the AMD
>> one also isn't (I think) prepared to be called more than once.
> 
> It's already called twice, there's one call to iommu_supports_x2apic
> in x2apic_bsp_setup and another one in iommu_enable_x2apic, so I think
> calling iommu_supports_x2apic multiple times is fine (or we would
> already have issues).

Ah, right - amd_iommu_prepare() bails (relatively) early when
noticing it had been called before.

Jan

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