Re: [Xen-devel] [RFC] Add the panic info when disable VT-d

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 19.01.15 at 10:00, <liang.z.li@xxxxxxxxx> wrote:
> --- a/xen/arch/x86/apic.c
> +++ b/xen/arch/x86/apic.c
> @@ -915,6 +915,11 @@ void __init x2apic_bsp_setup(void)
>              return;
>          }        
>          printk("x2APIC: Already enabled by BIOS: Ignoring cmdline 
> disable.\n");
> +    } else {
> +        if ( !iommu_enable) {
> +            panic("x2APIC should be disabled while IOMMU is disabled,"
> +                "try to set x2apic=0 in cmdline and disable x2apic in BIOS");
> +        }

Putting aside the coding style violations (figure braces on their own
lines, no hard tabs), you tie this to the wrong thing: You need
interrupt remapping to be enabled, whereas iommu_enable may
only mean DMA remapping. And I'm afraid you'd run into an
ordering problem (iommu_intremap getting set to its final value
vs. the code above being run) if you tried to correct this.

Jan


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