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 12:43, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote:

>> I retest version with removed NULL checks and in this case, my system
>> crashes.
>> So there has to be checks for NULL or something else is wrong.
> 
> Got a backtrace and Xen boot params? If you pass acpi=off, then
> disable_acpi() is invoked, and this sets acpi_disabled. If acpi_disabled=1,
> then iommu_setup() sets iommu_enabled=0. If iommu_enabled=0 then I think all
> the update_ire_from_* and similar hooks get disabled in the callers. So
> something unexpected must be happening.

Hmmm, perhaps this could be an early boot-time crash before iommu_setup() is
even called? Perhaps moving the if(acpi_disabled) iommu_enabled=0 somewhere
early-ish in setup.c:__start_xen(), with a warning message, would be the
right thing to do in that case (e.g., immediately after the call to
cmdline_parse()).

 -- Keir



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