linux-kernel - [RFC PATCH 13/13] KVM: SVM: Use fastpath x2apic IPI emulation when #vmexit with x2AVIC

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Date:   Sun, 20 Feb 2022 20:19:22 -0600
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>
CC:     <pbonzini@...hat.com>, <seanjc@...gle.com>, <joro@...tes.org>,
        <jon.grimm@....com>, <wei.huang2@....com>, <terry.bowman@....com>,
        "Suravee Suthikulpanit" <suravee.suthikulpanit@....com>
Subject: [RFC PATCH 13/13] KVM: SVM: Use fastpath x2apic IPI emulation when #vmexit with x2AVIC

When sends IPI to a halting vCPU, the hardware generates
avic_incomplete_ipi #vmexit with the
AVIC_IPI_FAILURE_TARGET_NOT_RUNNING reason.

For x2AVIC, enable fastpath emulation.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 arch/x86/kvm/svm/avic.c | 2 ++
 arch/x86/kvm/x86.c      | 3 ++-
 arch/x86/kvm/x86.h      | 1 +
 3 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 874c89f8fd47..758a79ee7f99 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -428,6 +428,8 @@ int avic_incomplete_ipi_interception(struct kvm_vcpu *vcpu)
 		kvm_lapic_reg_write(apic, APIC_ICR, icrl);
 		break;
 	case AVIC_IPI_FAILURE_TARGET_NOT_RUNNING:
+		handle_fastpath_set_x2apic_icr_irqoff(vcpu, svm->vmcb->control.exit_info_1);
+
 		/*
 		 * At this point, we expect that the AVIC HW has already
 		 * set the appropriate IRR bits on the valid target
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 641044db415d..c293027c7c10 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2008,7 +2008,7 @@ static inline bool kvm_vcpu_exit_request(struct kvm_vcpu *vcpu)
  * from guest to host, e.g. reacquiring KVM's SRCU lock. In contrast to the
  * other cases which must be called after interrupts are enabled on the host.
  */
-static int handle_fastpath_set_x2apic_icr_irqoff(struct kvm_vcpu *vcpu, u64 data)
+int handle_fastpath_set_x2apic_icr_irqoff(struct kvm_vcpu *vcpu, u64 data)
 {
 	if (!lapic_in_kernel(vcpu) || !apic_x2apic_mode(vcpu->arch.apic))
 		return 1;
@@ -2028,6 +2028,7 @@ static int handle_fastpath_set_x2apic_icr_irqoff(struct kvm_vcpu *vcpu, u64 data
 
 	return 1;
 }
+EXPORT_SYMBOL_GPL(handle_fastpath_set_x2apic_icr_irqoff);
 
 static int handle_fastpath_set_tscdeadline(struct kvm_vcpu *vcpu, u64 data)
 {
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 767ec7f99516..035d20f83ca6 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -286,6 +286,7 @@ int x86_decode_emulated_instruction(struct kvm_vcpu *vcpu, int emulation_type,
 int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 			    int emulation_type, void *insn, int insn_len);
 fastpath_t handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu);
+int handle_fastpath_set_x2apic_icr_irqoff(struct kvm_vcpu *vcpu, u64 data);
 
 extern u64 host_xcr0;
 extern u64 supported_xcr0;
-- 
2.25.1