[PATCH 1/3] KVM: MMU: Store nx bit for large page shadows

[Avi Kivity]

We need to distinguish between large page shadows which have the nx bit set
and those which don't.  The problem shows up when booting a newer smp Linux
kernel, where the trampoline page (which is in real mode, which uses the
same shadow pages as large pages) is using the same mapping as a kernel data
page, which is mapped using nx, causing kvm to spin on that page.

Signed-off-by: Avi Kivity <avi@xxxxxxxxxxxx>
---
 drivers/kvm/kvm.h         |    4 ++--
 drivers/kvm/paging_tmpl.h |    2 ++
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index a7c5e6b..65ab268 100644
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -121,7 +121,7 @@ struct kvm_pte_chain {
  *   bits 4:7 - page table level for this shadow (1-4)
  *   bits 8:9 - page table quadrant for 2-level guests
  *   bit   16 - "metaphysical" - gfn is not a real page (huge page/real mode)
- *   bits 17:18 - "access" - the user and writable bits of a huge page pde
+ *   bits 17:19 - "access" - the user, writable, and nx bits of a huge page pde
  */
 union kvm_mmu_page_role {
 	unsigned word;
@@ -131,7 +131,7 @@ union kvm_mmu_page_role {
 		unsigned quadrant : 2;
 		unsigned pad_for_nice_hex_output : 6;
 		unsigned metaphysical : 1;
-		unsigned hugepage_access : 2;
+		unsigned hugepage_access : 3;
 	};
 };
 
diff --git a/drivers/kvm/paging_tmpl.h b/drivers/kvm/paging_tmpl.h
index a7c5cb0..4b5391c 100644
--- a/drivers/kvm/paging_tmpl.h
+++ b/drivers/kvm/paging_tmpl.h
@@ -366,6 +366,8 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
 			metaphysical = 1;
 			hugepage_access = *guest_ent;
 			hugepage_access &= PT_USER_MASK | PT_WRITABLE_MASK;
+			if (*guest_ent & PT64_NX_MASK)
+				hugepage_access |= (1 << 2);
 			hugepage_access >>= PT_WRITABLE_SHIFT;
 			table_gfn = (*guest_ent & PT_BASE_ADDR_MASK)
 				>> PAGE_SHIFT;
-- 
1.5.2.4

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