Re: [Xen-devel] [PATCH RFC] pvh: set need_iommu early

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.01.15 at 22:49, <elena.ufimtseva@xxxxxxxxxx> wrote:
> On Thu, Jan 22, 2015 at 07:08:22AM +0000, Tian, Kevin wrote:
>> > From: Elena Ufimtseva [mailto:elena.ufimtseva@xxxxxxxxxx]
>> > Sent: Thursday, January 22, 2015 4:53 AM
>> > 
>> > need_iommu has to be set earler for dom0 pvh specific init
>> > functions. If not enabled, mmio regions are not mapped with iommu
>> > during domain construction.
>> > 
>> > This was discovered when working on booting problems of pvh dom0
>> > on two different machines (ThinkCentre M and Dell 5600T).
>> > On ThinkCentre during pvh dom0 booting process, IOMMU would report
>> > Page fault with EPT not present. The memory address of the page fault
>> > suggested that is mmio region for USB host controllers. The faulting
>> > address marked as Reserved in e820 map and is not part of any rmrr
>> > region reported by ACPI.
>> 
>> Need more understanding here. If iommu hasn't been setup for dom0 yet, 
>> why is there iommu page fault at that point?
> 
> Hi Kevin
> 
> Wrong wording.
> The page faults happen after iommu drhd are enabled.
> need_iommu only determines if the mapping will happed for mmio
> regions during pvh dom0 construction.

Please point out exactly which code this affects.

Jan


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