Re: [Xen-devel] [PATCH] AMD IOMMU: fail if there is no southbridge IO-APIC

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.02.14 at 16:12, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> wrote:
> On 02/07/2014 04:21 AM, Jan Beulich wrote:
>> ... but interrupt remapping is requested (with per-device remapping
>> tables). Without it, the timer interrupt is usually not working.
>>
>> Inspired by Linux'es "iommu/amd: Work around wrong IOAPIC device-id in
>> IVRS table" (commit c2ff5cf5294bcbd7fa50f7d860e90a66db7e5059) by Joerg
>> Roedel <joerg.roedel@xxxxxxx>.
>>
>> Reported-by: Eric Houby <ehouby@xxxxxxxxx>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> Tested-by: Eric Houby <ehouby@xxxxxxxxx>
>>
>> --- a/xen/drivers/passthrough/amd/iommu_acpi.c
>> +++ b/xen/drivers/passthrough/amd/iommu_acpi.c
>> @@ -984,6 +984,7 @@ static int __init parse_ivrs_table(struc
>>       const struct acpi_ivrs_header *ivrs_block;
>>       unsigned long length;
>>       unsigned int apic;
>> +    bool_t sb_ioapic = !iommu_intremap;
>>       int error = 0;
>>   
>>       BUG_ON(!table);
>> @@ -1017,8 +1018,15 @@ static int __init parse_ivrs_table(struc
>>       /* Each IO-APIC must have been mentioned in the table. */
>>       for ( apic = 0; !error && iommu_intremap && apic < nr_ioapics; ++apic )
>>       {
>> -        if ( !nr_ioapic_entries[apic] ||
>> -             ioapic_sbdf[IO_APIC_ID(apic)].pin_2_idx )
>> +        if ( !nr_ioapic_entries[apic] )
>> +            continue;
>> +
>> +        if ( !ioapic_sbdf[IO_APIC_ID(apic)].seg &&
>> +             /* SB IO-APIC is always on this device in AMD systems. */
>> +             ioapic_sbdf[IO_APIC_ID(apic)].bdf == PCI_BDF(0, 0x14, 0) )
>> +            sb_ioapic = 1;
>> +
>> +        if ( ioapic_sbdf[IO_APIC_ID(apic)].pin_2_idx )
>>               continue;
>>   
>>           if ( !test_bit(IO_APIC_ID(apic), ioapic_cmdline) )
> 
> I don't know whether 0:14:0 is set in stone, I don't remember seeing 
> anywhere that this is architectural.
> 
> In the (unlikely) event that it is moved somewhere else will the user be 
> able to overwrite where it is? Do you
> think that sb_ioapic may need to be set to true if appropriate bit is 
> set in ioapic_cmdline?

These are question you'd need to ask to JÃrg, the author of the
original Linux side patch. I took as a precondition here that he
knew what he was doing.

Jan

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