[Xen-devel] [PATCH RFC 11/14] xen: vmx: Added handle of SPP write protection fault

[Zhang Yi <yi.z.zhang@xxxxxxxxxxxxxxx>]

From: Zhang Yi Z <yi.z.zhang@xxxxxxxxxxxxxxx>

While hardware walking the SPP page table, If the sub-page
region write permission bit is set, the write is allowed,
else the write is disallowed and results in an EPT violation.

we need peek this case in EPT violation handler.

Signed-off-by: Zhang Yi Z <yi.z.zhang@xxxxxxxxx>
---
 xen/arch/x86/hvm/hvm.c        | 5 +++++
 xen/arch/x86/hvm/vmx/vmx.c    | 3 +++
 xen/arch/x86/mm/p2m-ept.c     | 2 ++
 xen/include/asm-x86/hvm/hvm.h | 2 ++
 xen/include/xen/mem_access.h  | 1 +
 5 files changed, 13 insertions(+)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index afc4620..a7ced32 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -1777,6 +1777,11 @@ int hvm_hap_nested_page_fault(paddr_t gpa, unsigned long 
gla,
         case p2m_access_rwx:
             violation = 0;
             break;
+        case p2m_access_spp:
+            printk("SPP: spp write protect: acc mode:%d\n", 
npfec.write_access);
+            violation = npfec.write_access;
+            rc = HVM_SPP_WRITE_PROTECTED;
+            goto out_put_gfn;
         }
 
         if ( violation )
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index a4c24bb..0481ffd 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -3295,6 +3295,9 @@ static void ept_handle_violation(ept_qual_t q, paddr_t 
gpa)
                         nestedhvm_paging_mode_hap(current ) )
             __vmwrite(EPT_POINTER, get_shadow_eptp(current));
         return;
+    case HVM_SPP_WRITE_PROTECTED:
+        update_guest_eip();
+        return;
     case -1:        // This vioaltion should be injected to L1 VMM
         vcpu_nestedhvm(current).nv_vmexit_pending = 1;
         return;
diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index c9dc29c..065beb9 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -214,6 +214,7 @@ static void ept_p2m_type_to_flags(struct p2m_domain *p2m, 
ept_entry_t *entry,
             entry->x = 0;
             break;           
         case p2m_access_rwx:
+        case p2m_access_spp:
             break;
     }
     
@@ -756,6 +757,7 @@ ept_spp_update_wp(struct p2m_domain *p2m, unsigned long gfn)
     new_entry = atomic_read_ept_entry(ept_entry);
     new_entry.spp = 1;
     new_entry.w = 0;
+    new_entry.access = p2m_access_spp;
     write_atomic(&(ept_entry->epte), new_entry.epte);
 
     ept_sync_domain(p2m);
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index b687e03..30c6775 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -80,6 +80,8 @@ enum hvm_intblk {
 #define HVM_EVENT_VECTOR_UNSET    (-1)
 #define HVM_EVENT_VECTOR_UPDATING (-2)
 
+#define HVM_SPP_WRITE_PROTECTED 2
+
 /*
  * The hardware virtual machine (HVM) interface abstracts away from the
  * x86/x86_64 CPU virtualization assist specifics. Currently this interface
diff --git a/xen/include/xen/mem_access.h b/xen/include/xen/mem_access.h
index 28eb70c..b5811dd 100644
--- a/xen/include/xen/mem_access.h
+++ b/xen/include/xen/mem_access.h
@@ -54,6 +54,7 @@ typedef enum {
     p2m_access_n2rwx = 9, /* Special: page goes from N to RWX on access, *
                            * generates an event but does not pause the
                            * vcpu */
+    p2m_access_spp = 0x0d,
 
     /* NOTE: Assumed to be only 4 bits right now on x86. */
 } p2m_access_t;
-- 
2.7.4


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