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

["Chen, Tiejun" <tiejun.chen@xxxxxxxxx>]

On 9/23/2015 11:56 PM, 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.
Based on your explanation, sounds pvh always creates this mapping 
beforehand, so what about this?
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index cf8485e..d026845 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -964,7 +964,7 @@ int set_identity_p2m_entry(struct domain *d, 
unsigned long gfn,
     struct p2m_domain *p2m = p2m_get_hostp2m(d);
     int ret;

-    if ( !paging_mode_translate(p2m->domain) )
+    if ( !paging_mode_translate(p2m->domain) || is_pvh_domain(d) )
     {
         if ( !need_iommu(d) )
             return 0;

Thanks
Tiejun

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