[PATCH v3 6/9] KVM: VMX: introduce vmx_need_pf_intercept

Mohammed Gamal
2020-07-10T15:49:15Z

From: Paolo Bonzini <pbonzini@redhat.com>

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/vmx/nested.c | 28 +++++++++++++++++-----------
arch/x86/kvm/vmx/vmx.c | 2 +-
arch/x86/kvm/vmx/vmx.h | 5 +++++
3 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index b26655104d4a..1aea9e3b8c43 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2433,22 +2433,28 @@ static void prepare_vmcs02_rare(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)

/*
* Whether page-faults are trapped is determined by a combination of
- * 3 settings: PFEC_MASK, PFEC_MATCH and EXCEPTION_BITMAP.PF.
- * If enable_ept, L0 doesn't care about page faults and we should
- * set all of these to L1's desires. However, if !enable_ept, L0 does
- * care about (at least some) page faults, and because it is not easy
- * (if at all possible?) to merge L0 and L1's desires, we simply ask
- * to exit on each and every L2 page fault. This is done by setting
- * MASK=MATCH=0 and (see below) EB.PF=1.
+ * 3 settings: PFEC_MASK, PFEC_MATCH and EXCEPTION_BITMAP.PF. If L0
+ * doesn't care about page faults then we should set all of these to
+ * L1's desires. However, if L0 does care about (some) page faults, it
+ * is not easy (if at all possible?) to merge L0 and L1's desires, we
+ * simply ask to exit on each and every L2 page fault. This is done by
+ * setting MASK=MATCH=0 and (see below) EB.PF=1.
* Note that below we don't need special code to set EB.PF beyond the
* "or"ing of the EB of vmcs01 and vmcs12, because when enable_ept,
* vmcs01's EB.PF is 0 so the "or" will take vmcs12's value, and when
* !enable_ept, EB.PF is 1, so the "or" will always be 1.
*/
- vmcs_write32(PAGE_FAULT_ERROR_CODE_MASK,
- enable_ept ? vmcs12->page_fault_error_code_mask : 0);
- vmcs_write32(PAGE_FAULT_ERROR_CODE_MATCH,
- enable_ept ? vmcs12->page_fault_error_code_match : 0);
+ if (vmx_need_pf_intercept(&vmx->vcpu)) {
+ /*
+ * TODO: if both L0 and L1 need the same MASK and MATCH,
+ * go ahead and use it?
+ */
+ vmcs_write32(PAGE_FAULT_ERROR_CODE_MASK, 0);
+ vmcs_write32(PAGE_FAULT_ERROR_CODE_MATCH, 0);
+ } else {
+ vmcs_write32(PAGE_FAULT_ERROR_CODE_MASK, vmcs12->page_fault_error_code_mask);
+ vmcs_write32(PAGE_FAULT_ERROR_CODE_MATCH, vmcs12->page_fault_error_code_match);
+ }

if (cpu_has_vmx_apicv()) {
vmcs_write64(EOI_EXIT_BITMAP0, vmcs12->eoi_exit_bitmap0);
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 178ee92551a9..770b090969fb 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -780,7 +780,7 @@ void update_exception_bitmap(struct kvm_vcpu *vcpu)
eb |= 1u << BP_VECTOR;
if (to_vmx(vcpu)->rmode.vm86_active)
eb = ~0;
- if (enable_ept)
+ if (!vmx_need_pf_intercept(vcpu))
eb &= ~(1u << PF_VECTOR);

/* When we are running a nested L2 guest and L1 specified for it a
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 639798e4a6ca..b0e5e210f1c1 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -550,6 +550,11 @@ static inline bool vmx_has_waitpkg(struct vcpu_vmx *vmx)
SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE;
}

+static inline bool vmx_need_pf_intercept(struct kvm_vcpu *vcpu)
+{
+ return !enable_ept;
+}
+
void dump_vmcs(void);

#endif /* __KVM_X86_VMX_H */
--
2.26.2