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



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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