[Xen-devel] [PATCH] nested EPT: fixing wrong handling for L2 guest's direct mmio access

[Yang Zhang <yang.z.zhang@xxxxxxxxx>]

From: Yang Zhang <yang.z.zhang@xxxxxxxxx>

L2 guest will access the physical device directly(nested VT-d). For such access,
Shadow EPT table should point to device's MMIO. But in current logic, L0 doesn't
distinguish the MMIO whether from qemu or physical device when building shadow 
EPT table.
This is wrong. This patch will setup the correct shadow EPT table for such MMIO 
ranges.

Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
---
 xen/arch/x86/mm/hap/nested_hap.c    |   10 ++++++++--
 xen/include/asm-x86/hvm/nestedhvm.h |    1 +
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/mm/hap/nested_hap.c b/xen/arch/x86/mm/hap/nested_hap.c
index c2ef1d1..38e2327 100644
--- a/xen/arch/x86/mm/hap/nested_hap.c
+++ b/xen/arch/x86/mm/hap/nested_hap.c
@@ -170,8 +170,11 @@ nestedhap_walk_L0_p2m(struct p2m_domain *p2m, paddr_t 
L1_gpa, paddr_t *L0_gpa,
     mfn = get_gfn_type_access(p2m, L1_gpa >> PAGE_SHIFT, p2mt, p2ma,
                               0, page_order);
 
+    rc = NESTEDHVM_PAGEFAULT_DIRECT_MMIO;
+    if ( *p2mt == p2m_mmio_direct )
+        goto direct_mmio_out;
     rc = NESTEDHVM_PAGEFAULT_MMIO;
-    if ( p2m_is_mmio(*p2mt) )
+    if ( *p2mt == p2m_mmio_dm )
         goto out;
 
     rc = NESTEDHVM_PAGEFAULT_L0_ERROR;
@@ -184,8 +187,9 @@ nestedhap_walk_L0_p2m(struct p2m_domain *p2m, paddr_t 
L1_gpa, paddr_t *L0_gpa,
     if ( !mfn_valid(mfn) )
         goto out;
 
-    *L0_gpa = (mfn_x(mfn) << PAGE_SHIFT) + (L1_gpa & ~PAGE_MASK);
     rc = NESTEDHVM_PAGEFAULT_DONE;
+direct_mmio_out:
+    *L0_gpa = (mfn_x(mfn) << PAGE_SHIFT) + (L1_gpa & ~PAGE_MASK);
 out:
     __put_gfn(p2m, L1_gpa >> PAGE_SHIFT);
     return rc;
@@ -245,6 +249,8 @@ nestedhvm_hap_nested_page_fault(struct vcpu *v, paddr_t 
*L2_gpa,
         break;
     case NESTEDHVM_PAGEFAULT_MMIO:
         return rv;
+    case NESTEDHVM_PAGEFAULT_DIRECT_MMIO:
+        break;
     default:
         BUG();
         break;
diff --git a/xen/include/asm-x86/hvm/nestedhvm.h 
b/xen/include/asm-x86/hvm/nestedhvm.h
index d8124cf..cca41b3 100644
--- a/xen/include/asm-x86/hvm/nestedhvm.h
+++ b/xen/include/asm-x86/hvm/nestedhvm.h
@@ -53,6 +53,7 @@ bool_t nestedhvm_vcpu_in_guestmode(struct vcpu *v);
 #define NESTEDHVM_PAGEFAULT_L0_ERROR   3
 #define NESTEDHVM_PAGEFAULT_MMIO       4
 #define NESTEDHVM_PAGEFAULT_RETRY      5
+#define NESTEDHVM_PAGEFAULT_DIRECT_MMIO 6
 int nestedhvm_hap_nested_page_fault(struct vcpu *v, paddr_t *L2_gpa,
     bool_t access_r, bool_t access_w, bool_t access_x);
 
-- 
1.7.1


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