Re: [Xen-devel] RE: [Xen-changelog] [xen-unstable]vt-d: Fixpanic in msi_msg_read_remap_rte with acpi=off

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 19/10/2009 15:46, "Cui, Dexuan" <dexuan.cui@xxxxxxxxx> wrote:

>> But, can't you reproduce the crash I mentioned before?
>> Please see the attached crash log -- I'm using c/s 20341:ea34183c5c11
>> and with "iommu=1 acpi=off" and I use a DQ35 host.
>> 
>> Actually what I care is the " if ( acpi_disabled ) iommu_enabled = 0".
> 
> BTW: from my crash log, you can see the bogus info -- actually the host
> doesn't support SC, QI and IR.
> (XEN) Intel VT-d Snoop Control supported.
> (XEN) Intel VT-d DMA Passthrough not supported.
> (XEN) Intel VT-d Queued Invalidation supported.
> (XEN) Intel VT-d Interrupt Remapping supported.
> (XEN) I/O virtualisation enabled

Ah, hm, well maybe you need that too. Actually I checked in a slightly
broader check as c/s 20342, which checks that !list_empty(acpi_drhd_units).
If you have no such units then initialising IOMMU support is rather
pointless. And if you did not do ACPI bootstrap then you cannot have parsed
any units. So the check is at least as strong as checking !acpi_disabled, I
think.

Hopefully everyone will be happy that this unlikely corner case, requiring
the user to have actually shot themselves in the foot by manually specifying
two contradictory boot parameters, is now solved to their satisfaction. ;-)

 -- Keir



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