Re: [Xen-devel] [BUG] After upgrade to Xen 4.12.0 iommu=no-igfx

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, Aug 02, 2019 at 10:05:40AM +0200, Roger Pau Monné wrote:
> On Thu, Aug 01, 2019 at 11:25:04AM -0700, Roman Shaposhnik wrote:
> > This patch completely fixes the problem for me!
> > 
> > Thanks Roger! I'd love to see this in Xen 4.13
> 
> Thanks for testing!
> 
> It's still not clear to me why the previous approach didn't work, but
> I think this patch is better because it removes the usage of
> {set/clear}_identity_p2m_entry from PV domains. I will submit this
> formally now.

Sorry to bother again, but since we still don't understand why the
previous fix didn't work for you, and I can't reproduce this with my
hardware, could you give the attached patch a try?

AFAICT the only difference between the non-working version and the
working version is the flush, so I've added it here.

Thanks, Roger.
---8<---
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index fef97c82f6..3605614aaf 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -1341,7 +1341,7 @@ int set_identity_p2m_entry(struct domain *d, unsigned 
long gfn_l,
 
     if ( !paging_mode_translate(p2m->domain) )
     {
-        if ( !need_iommu_pt_sync(d) )
+        if ( !has_iommu_pt(d) )
             return 0;
         return iommu_legacy_map(d, _dfn(gfn_l), _mfn(gfn_l), PAGE_ORDER_4K,
                                 IOMMUF_readable | IOMMUF_writable);
@@ -1432,7 +1432,7 @@ int clear_identity_p2m_entry(struct domain *d, unsigned 
long gfn_l)
 
     if ( !paging_mode_translate(d) )
     {
-        if ( !need_iommu_pt_sync(d) )
+        if ( !has_iommu_pt(d) )
             return 0;
         return iommu_legacy_unmap(d, _dfn(gfn_l), PAGE_ORDER_4K);
     }
diff --git a/xen/drivers/passthrough/vtd/iommu.c 
b/xen/drivers/passthrough/vtd/iommu.c
index 5d72270c5b..9fd5c97be2 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -2026,7 +2026,7 @@ static int rmrr_identity_mapping(struct domain *d, bool_t 
map,
     mrmrr->count = 1;
     list_add_tail(&mrmrr->list, &hd->arch.mapped_rmrrs);
 
-    return 0;
+    return iommu_iotlb_flush_all(d, IOMMU_FLUSHF_added | 
IOMMU_FLUSHF_modified);
 }
 
 static int intel_iommu_add_device(u8 devfn, struct pci_dev *pdev)


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