Re: [Xen-devel] Regression in RMRRs identity mapping for PVH Dom0

[Wei Liu <wei.liu2@xxxxxxxxxx>]

Hi Elena

On Wed, Sep 23, 2015 at 11:56:12AM -0400, Elena Ufimtseva wrote:
> Hi                                                                            
>   
>                                                                               
>   
> There is a regression in RMRR patch 5ae03990c120a7b3067a52d9784c9aa72c0705a6 
> in
> new set_identity_p2m_entry. RMRRs are not being mapped in IOMMU for PVH Dom0.
> This causes pages faults and some long 'hang-like' delays during boot and
> device assignments.
>                                                                               
>   
> During construct_dom0, in PVH path  p2m is being constructed and identity 
> mapped
> in IOMMU. The p2m type is p2m_mmio_direct and p2m access p2m_rwx.
> New code used to map RMRRs invoked from rmrr_identity_mapping                 
>   
> checks if p2m entry exists with same type and access and if yes, skips iommu
> mapping. Since there are p2m entries for pvh dom0 iomem, RMRRs are not being
> mapped in IOMMU.
>                                                                               
>   
> This debug patch attached fixes this and Ill be glad to see if there is a 
> more elegant fix.
>                                                                               
>   

From a release point of view, PVH Dom0 is not officially supported so I
don't consider this issue a blocker.

We can backport the proper fix to 4.6.1 if necessary, but I doubt this
is the only fix we need to make PVH Dom0 work on 4.6. Am I right?

Wei.

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