[Xen-devel] [PATCH 5/7] x86/shadow: Use the pagewalk reserved bits helpers

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

The shadow logic should never create a shadow of a guest PTE which contains
reserved bits from the guests point of view.  Such a shadowed entry might not
cause #PF[RSVD] when walked by hardware, thus won't behave architecturally
from the guests point of view.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
CC: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
---
 xen/arch/x86/mm/shadow/multi.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c
index 7c6b017..702835b 100644
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -2157,7 +2157,8 @@ static int validate_gl4e(struct vcpu *v, void *new_ge, 
mfn_t sl4mfn, void *se)
 
     perfc_incr(shadow_validate_gl4e_calls);
 
-    if ( guest_l4e_get_flags(new_gl4e) & _PAGE_PRESENT )
+    if ( (guest_l4e_get_flags(new_gl4e) & _PAGE_PRESENT) &&
+         !guest_l4e_rsvd_bits(v, new_gl4e) )
     {
         gfn_t gl3gfn = guest_l4e_get_gfn(new_gl4e);
         mfn_t gl3mfn = get_gfn_query_unlocked(d, gfn_x(gl3gfn), &p2mt);
@@ -2215,7 +2216,8 @@ static int validate_gl3e(struct vcpu *v, void *new_ge, 
mfn_t sl3mfn, void *se)
 
     perfc_incr(shadow_validate_gl3e_calls);
 
-    if ( guest_l3e_get_flags(new_gl3e) & _PAGE_PRESENT )
+    if ( (guest_l3e_get_flags(new_gl3e) & _PAGE_PRESENT) &&
+         !guest_l3e_rsvd_bits(v, new_gl3e) )
     {
         gfn_t gl2gfn = guest_l3e_get_gfn(new_gl3e);
         mfn_t gl2mfn = get_gfn_query_unlocked(d, gfn_x(gl2gfn), &p2mt);
@@ -2248,7 +2250,8 @@ static int validate_gl2e(struct vcpu *v, void *new_ge, 
mfn_t sl2mfn, void *se)
 
     perfc_incr(shadow_validate_gl2e_calls);
 
-    if ( guest_l2e_get_flags(new_gl2e) & _PAGE_PRESENT )
+    if ( (guest_l2e_get_flags(new_gl2e) & _PAGE_PRESENT) &&
+         !guest_l2e_rsvd_bits(v, new_gl2e) )
     {
         gfn_t gl1gfn = guest_l2e_get_gfn(new_gl2e);
         if ( guest_supports_superpages(v) &&
@@ -2288,8 +2291,7 @@ static int validate_gl1e(struct vcpu *v, void *new_ge, 
mfn_t sl1mfn, void *se)
     shadow_l1e_t new_sl1e;
     guest_l1e_t new_gl1e = *(guest_l1e_t *)new_ge;
     shadow_l1e_t *sl1p = se;
-    gfn_t gfn;
-    mfn_t gmfn;
+    mfn_t gmfn = INVALID_MFN;
     p2m_type_t p2mt;
     int result = 0;
 #if (SHADOW_OPTIMIZATIONS & SHOPT_OUT_OF_SYNC)
@@ -2298,8 +2300,13 @@ static int validate_gl1e(struct vcpu *v, void *new_ge, 
mfn_t sl1mfn, void *se)
 
     perfc_incr(shadow_validate_gl1e_calls);
 
-    gfn = guest_l1e_get_gfn(new_gl1e);
-    gmfn = get_gfn_query_unlocked(d, gfn_x(gfn), &p2mt);
+    if ( (guest_l1e_get_flags(new_gl1e) & _PAGE_PRESENT) &&
+         !guest_l1e_rsvd_bits(v, new_gl1e) )
+    {
+        gfn_t gfn = guest_l1e_get_gfn(new_gl1e);
+
+        gmfn = get_gfn_query_unlocked(d, gfn_x(gfn), &p2mt);
+    }
 
     l1e_propagate_from_guest(v, new_gl1e, gmfn, &new_sl1e, ft_prefetch, p2mt);
     result |= shadow_set_l1e(d, sl1p, new_sl1e, p2mt, sl1mfn);
-- 
2.1.4


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