linux-kernel - [PATCH v13 08/48] KVM: x86: hyper-v: Resurrect dedicated KVM_REQ_HV_TLB

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Date:   Tue,  1 Nov 2022 15:53:46 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Siddharth Chandrasekaran <sidcha@...zon.de>,
        Yuan Yao <yuan.yao@...ux.intel.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v13 08/48] KVM: x86: hyper-v: Resurrect dedicated KVM_REQ_HV_TLB_FLUSH flag

In preparation to implementing fine-grained Hyper-V TLB flush and
L2 TLB flush, resurrect dedicated KVM_REQ_HV_TLB_FLUSH request bit. As
KVM_REQ_TLB_FLUSH_GUEST is a stronger operation, clear KVM_REQ_HV_TLB_FLUSH
request in kvm_vcpu_flush_tlb_guest().

The flush itself is temporary handled by kvm_vcpu_flush_tlb_guest().

No functional change intended.

Reviewed-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/include/asm/kvm_host.h | 2 ++
 arch/x86/kvm/hyperv.c           | 4 ++--
 arch/x86/kvm/svm/svm.c          | 7 +++++++
 arch/x86/kvm/x86.c              | 9 +++++++++
 4 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 50fe0c7a5571..05d90e11e535 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -108,6 +108,8 @@
 	KVM_ARCH_REQ_FLAGS(30, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
 #define KVM_REQ_MMU_FREE_OBSOLETE_ROOTS \
 	KVM_ARCH_REQ_FLAGS(31, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
+#define KVM_REQ_HV_TLB_FLUSH \
+	KVM_ARCH_REQ_FLAGS(32, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
 
 #define CR0_RESERVED_BITS                                               \
 	(~(unsigned long)(X86_CR0_PE | X86_CR0_MP | X86_CR0_EM | X86_CR0_TS \
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 0adf4a437e85..3c0f639f6a05 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1870,11 +1870,11 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
 	 * analyze it here, flush TLB regardless of the specified address space.
 	 */
 	if (all_cpus) {
-		kvm_make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH_GUEST);
+		kvm_make_all_cpus_request(kvm, KVM_REQ_HV_TLB_FLUSH);
 	} else {
 		sparse_set_to_vcpu_mask(kvm, sparse_banks, valid_bank_mask, vcpu_mask);
 
-		kvm_make_vcpus_request_mask(kvm, KVM_REQ_TLB_FLUSH_GUEST, vcpu_mask);
+		kvm_make_vcpus_request_mask(kvm, KVM_REQ_HV_TLB_FLUSH, vcpu_mask);
 	}
 
 ret_success:
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 58f0077d9357..9210a8840224 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3738,6 +3738,13 @@ static void svm_flush_tlb_current(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 
+	/*
+	 * Unlike VMX, SVM doesn't provide a way to flush only NPT TLB entries.
+	 * A TLB flush for the current ASID flushes both "host" and "guest" TLB
+	 * entries, and thus is a superset of Hyper-V's fine grained flushing.
+	 */
+	kvm_clear_request(KVM_REQ_HV_TLB_FLUSH, vcpu);
+
 	/*
 	 * Flush only the current ASID even if the TLB flush was invoked via
 	 * kvm_flush_remote_tlbs().  Although flushing remote TLBs requires all
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fdda5f447f87..bf2aa77b7a2f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3417,6 +3417,12 @@ static void kvm_vcpu_flush_tlb_guest(struct kvm_vcpu *vcpu)
 	}
 
 	static_call(kvm_x86_flush_tlb_guest)(vcpu);
+
+	/*
+	 * Flushing all "guest" TLB is always a superset of Hyper-V's fine
+	 * grained flushing.
+	 */
+	kvm_clear_request(KVM_REQ_HV_TLB_FLUSH, vcpu);
 }
 
 
@@ -10491,6 +10497,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 
 		kvm_service_local_tlb_flush_requests(vcpu);
 
+		if (kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu))
+			kvm_vcpu_flush_tlb_guest(vcpu);
+
 		if (kvm_check_request(KVM_REQ_REPORT_TPR_ACCESS, vcpu)) {
 			vcpu->run->exit_reason = KVM_EXIT_TPR_ACCESS;
 			r = 0;
-- 
2.37.3