[Xen-changelog] [xen stable-4.2] x86/HVM: consolidate passthrough handling in epte_get_entry_emt()

[patchbot@xxxxxxx]

commit ea3db636df531428320e6ab61479731be283ac23
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Mar 14 17:52:27 2014 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Mar 14 17:52:27 2014 +0100

    x86/HVM: consolidate passthrough handling in epte_get_entry_emt()
    
    It is inconsistent to depend on iommu_enabled alone: For a guest
    without devices passed through to it, it is of no concern whether the
    IOMMU is enabled.
    
    There's one rather special case to take care of: VMX code marks the
    LAPIC access page as MMIO. The added assertion needs to take this into
    consideration, and the subsequent handling of the direct MMIO case was
    inconsistent too: That page would have been WB in the absence of an
    IOMMU, but UC in the presence of it, while in fact the cachabilty of
    this page is entirely unrelated to an IOMMU being in use.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: "Xu, Dongxiao" <dongxiao.xu@xxxxxxxxx>
    Acked-by: Keir Fraser <keir@xxxxxxx>
    master commit: 3089a6d82bdf3112ccb1dd074ce34a8cbdc4ccd8
    master date: 2014-03-10 11:04:36 +0100
---
 xen/arch/x86/hvm/mtrr.c    |   10 ++++++++--
 xen/arch/x86/hvm/vmx/vmx.c |    2 +-
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/hvm/mtrr.c b/xen/arch/x86/hvm/mtrr.c
index e56d270..1e84e35 100644
--- a/xen/arch/x86/hvm/mtrr.c
+++ b/xen/arch/x86/hvm/mtrr.c
@@ -698,14 +698,20 @@ uint8_t epte_get_entry_emt(struct domain *d, unsigned 
long gfn, mfn_t mfn,
     if ( hvm_get_mem_pinned_cacheattr(d, gfn, &type) )
         return type;
 
-    if ( !iommu_enabled )
+    if ( !iommu_enabled ||
+         (rangeset_is_empty(d->iomem_caps) &&
+          rangeset_is_empty(d->arch.ioport_caps) &&
+          !has_arch_pdevs(d)) )
     {
+        ASSERT(!direct_mmio ||
+               mfn_x(mfn) == d->arch.hvm_domain.vmx.apic_access_mfn);
         *ipat = 1;
         return MTRR_TYPE_WRBACK;
     }
 
     if ( direct_mmio )
-        return MTRR_TYPE_UNCACHABLE;
+        return mfn_x(mfn) != d->arch.hvm_domain.vmx.apic_access_mfn
+               ? MTRR_TYPE_UNCACHABLE : MTRR_TYPE_WRBACK;
 
     if ( iommu_snoop )
     {
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index f7c1130..1bf0297 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2006,9 +2006,9 @@ static int vmx_alloc_vlapic_mapping(struct domain *d)
     if ( apic_va == NULL )
         return -ENOMEM;
     share_xen_page_with_guest(virt_to_page(apic_va), d, XENSHARE_writable);
+    d->arch.hvm_domain.vmx.apic_access_mfn = virt_to_mfn(apic_va);
     set_mmio_p2m_entry(d, paddr_to_pfn(APIC_DEFAULT_PHYS_BASE),
         _mfn(virt_to_mfn(apic_va)));
-    d->arch.hvm_domain.vmx.apic_access_mfn = virt_to_mfn(apic_va);
 
     return 0;
 }
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.2

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