Re: [Xen-devel] [PATCH v2 4/4] x86/mm/p2m: stop checking for IOMMU shared page tables in mmio_order()

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 04 December 2018 15:21
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Roger Pau Monne
> <roger.pau@xxxxxxxxxx>; Wei Liu <wei.liu2@xxxxxxxxxx>; George Dunlap
> <George.Dunlap@xxxxxxxxxx>; xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
> Subject: Re: [PATCH v2 4/4] x86/mm/p2m: stop checking for IOMMU shared
> page tables in mmio_order()
> 
> >>> On 03.12.18 at 18:40, <paul.durrant@xxxxxxxxxx> wrote:
> > Now that the iommu_map() and iommu_unmap() operations take an order
> > parameter and elide flushing there's no strong reason why modifying MMIO
> > ranges in the p2m should be restricted to a 4k granularity simply
> because
> > the IOMMU is enabled but shared page tables are not in operation.
> 
> I'm afraid the two improvements are not enough for this restriction
> to be lifted: There's still no preemption in the processing of the
> higher order values.

Why? 1G orders are already ruled out and testing shows that 2M orders cause no 
problems on EPYC systems.

  Paul

> 
> Jan
> 


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel