[Xen-devel] [PATCH 1/2] x86/mem_event: Deliver gla fault EPT violation information

[Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>]

On Intel EPT the exit qualification generated by a violation also includes a 
bit (EPT_GLA_FAULT) which describes the following information:
Set if the access causing the EPT violation is to a guest-physical address that 
is the translation of a linear address. Clear if the access causing the EPT 
violation is to a paging-structure entry as part of a page walk or the update 
of an accessed or dirty bit.

For more information see Table 27-7 in the Intel SDM.

This patch extends the mem_event system to deliver this extra information, 
which could be useful for determining the cause of a violation.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>
---
 xen/arch/x86/hvm/hvm.c         | 6 ++++--
 xen/arch/x86/hvm/svm/svm.c     | 2 +-
 xen/arch/x86/hvm/vmx/vmx.c     | 4 +++-
 xen/arch/x86/mm/p2m.c          | 7 ++++---
 xen/include/asm-x86/hvm/hvm.h  | 4 +++-
 xen/include/asm-x86/p2m.h      | 6 +++---
 xen/include/public/mem_event.h | 3 ++-
 7 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index e834406..b09a905 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -2724,6 +2724,7 @@ void hvm_inject_page_fault(int errcode, unsigned long cr2)
 
 int hvm_hap_nested_page_fault(paddr_t gpa,
                               bool_t gla_valid,
+                              bool_t gla_fault,
                               unsigned long gla,
                               bool_t access_r,
                               bool_t access_w,
@@ -2832,8 +2833,9 @@ int hvm_hap_nested_page_fault(paddr_t gpa,
 
         if ( violation )
         {
-            if ( p2m_mem_access_check(gpa, gla_valid, gla, access_r, 
-                                        access_w, access_x, &req_ptr) )
+            if ( p2m_mem_access_check(gpa, gla_valid, gla_fault, gla,
+                                        access_r, access_w, access_x,
+                                        &req_ptr) )
             {
                 fall_through = 1;
             } else {
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 76616ac..1dbb12f 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -1403,7 +1403,7 @@ static void svm_do_nested_pgfault(struct vcpu *v,
     p2m_access_t p2ma;
     struct p2m_domain *p2m = NULL;
 
-    ret = hvm_hap_nested_page_fault(gpa, 0, ~0ul, 
+    ret = hvm_hap_nested_page_fault(gpa, 0, 0, ~0ul,
                                     1, /* All NPFs count as reads */
                                     npfec & PFEC_write_access, 
                                     npfec & PFEC_insn_fetch);
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 2caa04a..0bd77b3 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2375,7 +2375,9 @@ static void ept_handle_violation(unsigned long 
qualification, paddr_t gpa)
     else
         gla = ~0ull;
     ret = hvm_hap_nested_page_fault(gpa,
-                                    !!(qualification & EPT_GLA_VALID), gla,
+                                    !!(qualification & EPT_GLA_VALID),
+                                    !!(qualification & EPT_GLA_FAULT),
+                                    gla,
                                     !!(qualification & EPT_READ_VIOLATION),
                                     !!(qualification & EPT_WRITE_VIOLATION),
                                     !!(qualification & EPT_EXEC_VIOLATION));
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index bca9f0f..303dc2b 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -1323,9 +1323,9 @@ void p2m_mem_paging_resume(struct domain *d)
     }
 }
 
-bool_t p2m_mem_access_check(paddr_t gpa, bool_t gla_valid, unsigned long gla, 
-                          bool_t access_r, bool_t access_w, bool_t access_x,
-                          mem_event_request_t **req_ptr)
+bool_t p2m_mem_access_check(paddr_t gpa, bool_t gla_valid, bool_t gla_fault,
+                          unsigned long gla, bool_t access_r, bool_t access_w,
+                          bool_t access_x, mem_event_request_t **req_ptr)
 {
     struct vcpu *v = current;
     unsigned long gfn = gpa >> PAGE_SHIFT;
@@ -1404,6 +1404,7 @@ bool_t p2m_mem_access_check(paddr_t gpa, bool_t 
gla_valid, unsigned long gla,
         req->gfn = gfn;
         req->offset = gpa & ((1 << PAGE_SHIFT) - 1);
         req->gla_valid = gla_valid;
+        req->gla_fault = gla_fault;
         req->gla = gla;
         req->access_r = access_r;
         req->access_w = access_w;
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index 0ebd478..38562ff 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -456,7 +456,9 @@ static inline void hvm_invalidate_regs_fields(struct 
cpu_user_regs *regs)
 }
 
 int hvm_hap_nested_page_fault(paddr_t gpa,
-                              bool_t gla_valid, unsigned long gla,
+                              bool_t gla_valid,
+                              bool_t gla_fault,
+                              unsigned long gla,
                               bool_t access_r,
                               bool_t access_w,
                               bool_t access_x);
diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
index 0ddbadb..8616fda 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -597,9 +597,9 @@ void p2m_mem_paging_resume(struct domain *d);
  * been promoted with no underlying vcpu pause. If the req_ptr has been 
populated, 
  * then the caller must put the event in the ring (once having released 
get_gfn*
  * locks -- caller must also xfree the request. */
-bool_t p2m_mem_access_check(paddr_t gpa, bool_t gla_valid, unsigned long gla, 
-                          bool_t access_r, bool_t access_w, bool_t access_x,
-                          mem_event_request_t **req_ptr);
+bool_t p2m_mem_access_check(paddr_t gpa, bool_t gla_valid, bool_t gla_fault,
+                          unsigned long gla, bool_t access_r, bool_t access_w,
+                          bool_t access_x, mem_event_request_t **req_ptr);
 /* Resumes the running of the VCPU, restarting the last instruction */
 void p2m_mem_access_resume(struct domain *d);
 
diff --git a/xen/include/public/mem_event.h b/xen/include/public/mem_event.h
index 3831b41..5785ff9 100644
--- a/xen/include/public/mem_event.h
+++ b/xen/include/public/mem_event.h
@@ -62,7 +62,8 @@ typedef struct mem_event_st {
     uint16_t access_w:1;
     uint16_t access_x:1;
     uint16_t gla_valid:1;
-    uint16_t available:12;
+    uint16_t gla_fault:1;
+    uint16_t available:11;
 
     uint16_t reason;
 } mem_event_request_t, mem_event_response_t;
-- 
2.0.1


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