[RFC PATCH 2/4] mmu: Update ept specific valid bit values

[Bandan Das <bsd@redhat.com>]

Until now , is_present_gpte checks for all bits set (XWR) and
is_shadow_present_pte() checks for the present bit set. To support
execute only mappings we should teach these functions to distinguish 100
as valid based on host support.

Signed-off-by: Bandan Das <bsd@redhat.com>
---
 arch/x86/kvm/mmu.c         | 5 ++++-
 arch/x86/kvm/paging_tmpl.h | 7 ++++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 37b01b1..57d8696 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -308,7 +308,10 @@ static int is_nx(struct kvm_vcpu *vcpu)
 
 static int is_shadow_present_pte(u64 pte)
 {
-	return pte & PT_PRESENT_MASK && !is_mmio_spte(pte);
+	int xbit = shadow_xonly_valid ? pte & shadow_x_mask : 0;
+
+	return (pte & PT_PRESENT_MASK) | xbit
+		&& !is_mmio_spte(pte);
 }
 
 static int is_large_pte(u64 pte)
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index bc019f7..9f5bd06 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -133,7 +133,12 @@ static inline int FNAME(is_present_gpte)(unsigned long pte)
 #if PTTYPE != PTTYPE_EPT
 	return is_present_gpte(pte);
 #else
-	return pte & 7;
+	/*
+	 * For EPT, bits [2:0] can be 001, 100 or 111
+	 * Further, for 100, logical processor should support
+	 * execute-only.
+	 */
+	return (pte & 1) || (shadow_xonly_valid && (pte & 4));
 #endif
 }
 
-- 
2.5.5