[PATCH 3/3] KVM: x86: quirkily apply WB to all memory if cache is disabled

[Xiao Guangrong <guangrong.xiao@linux.intel.com>]

From: Xiao Guangrong <guangrong.xiao@intel.com>

Current firmware depends on WB to fast boot, please refer to
      https://lkml.org/lkml/2015/7/12/115

Let's us WB if CR0.CD is set to make this kind of firmware happy

This quirk can be dropped by using KVM_ENABLE_CAP API with
KVM_CAP_DISABLE_QUIRKS if the broken firmware is gone

Signed-off-by: Xiao Guangrong <guangrong.xiao@intel.com>
---
 arch/x86/include/uapi/asm/kvm.h | 1 +
 arch/x86/kvm/lapic.c            | 2 +-
 arch/x86/kvm/svm.c              | 2 +-
 arch/x86/kvm/vmx.c              | 5 ++++-
 arch/x86/kvm/x86.c              | 7 +++++++
 arch/x86/kvm/x86.h              | 5 +++++
 6 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index a4ae82e..2f141d4 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -356,5 +356,6 @@ struct kvm_sync_regs {
 
 #define KVM_QUIRK_LINT0_REENABLED	(1 << 0)
 #define KVM_QUIRK_CD_NW_CLEARED		(1 << 1)
+#define KVM_QUIRK_CD_AS_WB		(1 << 2)
 
 #endif /* _ASM_X86_KVM_H */
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 954e98a..0d77b20 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1595,7 +1595,7 @@ void kvm_lapic_reset(struct kvm_vcpu *vcpu, bool init_event)
 	for (i = 0; i < APIC_LVT_NUM; i++)
 		apic_set_reg(apic, APIC_LVTT + 0x10 * i, APIC_LVT_MASKED);
 	apic_update_lvtt(apic);
-	if (!(vcpu->kvm->arch.disabled_quirks & KVM_QUIRK_LINT0_REENABLED))
+	if (!kvm_check_disabled_quirks(vcpu->kvm, KVM_QUIRK_LINT0_REENABLED))
 		apic_set_reg(apic, APIC_LVT0,
 			     SET_APIC_DELIVERY_MODE(0, APIC_MODE_EXTINT));
 	apic_manage_nmi_watchdog(apic, kvm_apic_get_reg(apic, APIC_LVT0));
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index bbc678a..cac9ee6 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1672,7 +1672,7 @@ static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 	 * does not do it - this results in some delay at
 	 * reboot
 	 */
-	if (!(vcpu->kvm->arch.disabled_quirks & KVM_QUIRK_CD_NW_CLEARED))
+	if (!kvm_check_disabled_quirks(vcpu->kvm, KVM_QUIRK_CD_NW_CLEARED))
 		cr0 &= ~(X86_CR0_CD | X86_CR0_NW);
 	svm->vmcb->save.cr0 = cr0;
 	mark_dirty(svm->vmcb, VMCB_CR);
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index d342b23..74398db 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8703,7 +8703,10 @@ static u64 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
 
 	if (kvm_read_cr0(vcpu) & X86_CR0_CD) {
 		ipat = VMX_EPT_IPAT_BIT;
-		cache = MTRR_TYPE_UNCACHABLE;
+		if (kvm_check_disabled_quirks(vcpu->kvm, KVM_QUIRK_CD_AS_WB))
+			cache = MTRR_TYPE_WRBACK;
+		else
+			cache = MTRR_TYPE_UNCACHABLE;
 		goto exit;
 	}
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 28076c2..fd21712 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3575,6 +3575,11 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 	return r;
 }
 
+static void kvm_init_disabled_quirks(struct kvm *kvm)
+{
+	kvm->arch.disabled_quirks = KVM_QUIRK_CD_AS_WB;
+}
+
 long kvm_arch_vm_ioctl(struct file *filp,
 		       unsigned int ioctl, unsigned long arg)
 {
@@ -7422,6 +7427,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	INIT_DELAYED_WORK(&kvm->arch.kvmclock_update_work, kvmclock_update_fn);
 	INIT_DELAYED_WORK(&kvm->arch.kvmclock_sync_work, kvmclock_sync_fn);
 
+	kvm_init_disabled_quirks(kvm);
+
 	return 0;
 }
 
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index c04b56b..ea99928 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -152,6 +152,11 @@ static inline u64 get_kernel_ns(void)
 	return ktime_get_boot_ns();
 }
 
+static inline bool kvm_check_disabled_quirks(struct kvm *kvm, u64 quirk)
+{
+	return !!(kvm->arch.disabled_quirks & quirk);
+}
+
 void kvm_before_handle_nmi(struct kvm_vcpu *vcpu);
 void kvm_after_handle_nmi(struct kvm_vcpu *vcpu);
 void kvm_set_pending_timer(struct kvm_vcpu *vcpu);
-- 
2.1.0