[PATCH v6 2/5] KVM: x86: Dirty quota-based throttling of vcpus

[Shivam Kumar <shivam.kumar1@nutanix.com>]

Exit to userspace whenever the dirty quota is exhausted (i.e. dirty count
equals/exceeds dirty quota) to request more dirty quota.

Suggested-by: Shaju Abraham <shaju.abraham@nutanix.com>
Suggested-by: Manish Mishra <manish.mishra@nutanix.com>
Co-developed-by: Anurag Madnawat <anurag.madnawat@nutanix.com>
Signed-off-by: Anurag Madnawat <anurag.madnawat@nutanix.com>
Signed-off-by: Shivam Kumar <shivam.kumar1@nutanix.com>
---
 arch/x86/kvm/mmu/spte.c | 4 ++--
 arch/x86/kvm/vmx/vmx.c  | 3 +++
 arch/x86/kvm/x86.c      | 9 +++++++++
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c
index 2e08b2a45361..c0ed35abbf2d 100644
--- a/arch/x86/kvm/mmu/spte.c
+++ b/arch/x86/kvm/mmu/spte.c
@@ -228,9 +228,9 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
 		  "spte = 0x%llx, level = %d, rsvd bits = 0x%llx", spte, level,
 		  get_rsvd_bits(&vcpu->arch.mmu->shadow_zero_check, spte, level));
 
-	if ((spte & PT_WRITABLE_MASK) && kvm_slot_dirty_track_enabled(slot)) {
+	if (spte & PT_WRITABLE_MASK) {
 		/* Enforced by kvm_mmu_hugepage_adjust. */
-		WARN_ON(level > PG_LEVEL_4K);
+		WARN_ON(level > PG_LEVEL_4K && kvm_slot_dirty_track_enabled(slot));
 		mark_page_dirty_in_slot(vcpu->kvm, slot, gfn);
 	}
 
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c9b49a09e6b5..140a5511ed45 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5749,6 +5749,9 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
 		 */
 		if (__xfer_to_guest_mode_work_pending())
 			return 1;
+
+		if (!kvm_vcpu_check_dirty_quota(vcpu))
+			return 0;
 	}
 
 	return 1;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 43a6a7efc6ec..8447e70b26f5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10379,6 +10379,15 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 			r = 0;
 			goto out;
 		}
+		if (kvm_check_request(KVM_REQ_DIRTY_QUOTA_EXIT, vcpu)) {
+			struct kvm_run *run = vcpu->run;
+
+			run->exit_reason = KVM_EXIT_DIRTY_QUOTA_EXHAUSTED;
+			run->dirty_quota_exit.count = vcpu->stat.generic.pages_dirtied;
+			run->dirty_quota_exit.quota = vcpu->dirty_quota;
+			r = 0;
+			goto out;
+		}
 
 		/*
 		 * KVM_REQ_HV_STIMER has to be processed after
-- 
2.22.3