[PATCH 05/15] KVM: nVMX: Don't rewrite GUEST_PML_INDEX during nested VM-Entry

Sean Christopherson
2019-05-07T16:07:15Z

Emulation of GUEST_PML_INDEX for a nested VMM is a bit weird. Because
L0 flushes the PML on every VM-Exit, the value in vmcs02 at the time of
VM-Enter is a constant -1, regardless of what L1 thinks/wants.

Fixes: 09abe32002665 ("KVM: nVMX: split pieces of prepare_vmcs02() to prepare_vmcs02_early()")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/kvm/vmx/nested.c | 20 +++++++++-----------
1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 094d139579fb..a30d53823b2e 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -1945,8 +1945,16 @@ static void prepare_vmcs02_constant_state(struct vcpu_vmx *vmx)
if (cpu_has_vmx_msr_bitmap())
vmcs_write64(MSR_BITMAP, __pa(vmx->nested.vmcs02.msr_bitmap));

- if (enable_pml)
+ /*
+ * Conceptually we want to copy the PML address and index from vmcs01
+ * here, and then back to vmcs01 on nested vmexit. But since we always
+ * flush the log on each vmexit and never change the PML address (once
+ * set), both fields are effectively constant in vmcs02.
+ */
+ if (enable_pml) {
vmcs_write64(PML_ADDRESS, page_to_phys(vmx->pml_pg));
+ vmcs_write16(GUEST_PML_INDEX, PML_ENTITY_NUM - 1);
+ }

if (cpu_has_vmx_encls_vmexit())
vmcs_write64(ENCLS_EXITING_BITMAP, -1ull);
@@ -2106,16 +2114,6 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
exec_control |= VM_EXIT_LOAD_IA32_EFER;
vm_exit_controls_init(vmx, exec_control);

- /*
- * Conceptually we want to copy the PML address and index from
- * vmcs01 here, and then back to vmcs01 on nested vmexit. But,
- * since we always flush the log on each vmexit and never change
- * the PML address (once set), this happens to be equivalent to
- * simply resetting the index in vmcs02.
- */
- if (enable_pml)
- vmcs_write16(GUEST_PML_INDEX, PML_ENTITY_NUM - 1);
-
/*
* Interrupt/Exception Fields
*/
--
2.21.0