[PATCH v3] KVM: vmx: fix ept reserved bits for 1-GByte page

Wanpeng Li
2014-08-20T03:15:28Z

EPT misconfig handler in kvm will check which reason lead to EPT
misconfiguration after vmexit. One of the reasons is that an EPT
paging-structure entry is configured with settings reserved for
future functionality. However, the handler can't identify if
paging-structure entry of reserved bits for 1-GByte page are
configured, since PDPTE which point to 1-GByte page will reserve
bits 29:12 instead of bits 7:3 which are reserved for PDPTE that
references an EPT Page Directory. This patch fix it by reserve
bits 29:12 for 1-GByte page.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
v2 -> v3:
* return 0xf8 for level == 4
* check spte & (1ULL << 7) if level == 1
* (rsvd_mask & 0x38) == 0 for large page or leaf page
v1 -> v2:
* same "if" statement cover both 2MB and 1GB pages
* return 0xf8 for level == 4
* get the level by checking the return value of ept_rsvd_mask

arch/x86/kvm/vmx.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index cad37d5..3218359 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5521,17 +5521,18 @@ static u64 ept_rsvd_mask(u64 spte, int level)
for (i = 51; i > boot_cpu_data.x86_phys_bits; i--)
mask |= (1ULL << i);

- if (level > 2)
+ if (level == 4)
/* bits 7:3 reserved */
mask |= 0xf8;
- else if (level == 2) {
- if (spte & (1ULL << 7))
- /* 2MB ref, bits 20:12 reserved */
- mask |= 0x1ff000;
- else
- /* bits 6:3 reserved */
- mask |= 0x78;
- }
+ else if (spte & (1ULL << 7))
+ /*
+ * 1GB/2MB page, bits 29:12 or 20:12 reserved respectively,
+ * level == 1 if the hypervisor is using the ignored bit 7.
+ */
+ mask |= (PAGE_SIZE << ((level - 1) * 9)) - PAGE_SIZE;
+ else
+ /* bits 6:3 reserved */
+ mask |= 0x78;

return mask;
}
@@ -5561,7 +5562,8 @@ static void ept_misconfig_inspect_spte(struct kvm_vcpu *vcpu, u64 spte,
WARN_ON(1);
}

- if (level == 1 || (level == 2 && (spte & (1ULL << 7)))) {
+ /* bits 5:3 are _not_ reserved for large page or leaf page */
+ if ((rsvd_bits & 0x38) == 0) {
u64 ept_mem_type = (spte & 0x38) >> 3;

if (ept_mem_type == 2 || ept_mem_type == 3 ||
--
1.9.1