[PATCH v2 05/11] KVM: arm64: Defer WFI emulation as a requested event

From: Oliver Upton <oupton@google.com>
To: kvmarm@lists.cs.columbia.edu
Cc: Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Andrew Jones <drjones@redhat.com>,
	Peter Shier <pshier@google.com>,
	Ricardo Koller <ricarkol@google.com>,
	Reiji Watanabe <reijiw@google.com>,
	Raghavendra Rao Anata <rananta@google.com>,
	kvm@vger.kernel.org, Oliver Upton <oupton@google.com>
Subject: [PATCH v2 05/11] KVM: arm64: Defer WFI emulation as a requested event
Date: Thu, 23 Sep 2021 19:16:04 +0000	[thread overview]
Message-ID: <20210923191610.3814698-6-oupton@google.com> (raw)
In-Reply-To: <20210923191610.3814698-1-oupton@google.com>

The emulation of WFI-like instructions (WFI, PSCI CPU_SUSPEND) is done
by calling kvm_vcpu_block() directly from the respective exit handlers.
A subsequent change to KVM will allow userspace to request a vCPU be
suspended on the next KVM_RUN, necessitating a deferral mechanism for
WFI emulation.

Refactor such that there is a single WFI implementation which may be
requested with KVM_REQ_SUSPEND. Request WFI emulation from the
aforementioned handlers by making this request.

Signed-off-by: Oliver Upton <oupton@google.com>
---
 arch/arm64/include/asm/kvm_host.h | 1 +
 arch/arm64/kvm/arm.c              | 9 +++++++++
 arch/arm64/kvm/handle_exit.c      | 3 +--
 arch/arm64/kvm/psci.c             | 4 +---
 4 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index f8be56d5342b..1beda1189a15 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -47,6 +47,7 @@
 #define KVM_REQ_RECORD_STEAL	KVM_ARCH_REQ(3)
 #define KVM_REQ_RELOAD_GICv4	KVM_ARCH_REQ(4)
 #define KVM_REQ_RELOAD_PMU	KVM_ARCH_REQ(5)
+#define KVM_REQ_SUSPEND		KVM_ARCH_REQ(6)
 
 #define KVM_DIRTY_LOG_MANUAL_CAPS   (KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE | \
 				     KVM_DIRTY_LOG_INITIALLY_SET)
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 3d4acd354f94..f1a375648e25 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -670,6 +670,12 @@ static void kvm_vcpu_sleep(struct kvm_vcpu *vcpu)
 	smp_rmb();
 }
 
+static void kvm_vcpu_suspend(struct kvm_vcpu *vcpu)
+{
+	kvm_vcpu_block(vcpu);
+	kvm_clear_request(KVM_REQ_UNHALT, vcpu);
+}
+
 static int kvm_vcpu_initialized(struct kvm_vcpu *vcpu)
 {
 	return vcpu->arch.target >= 0;
@@ -681,6 +687,9 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu)
 		if (kvm_check_request(KVM_REQ_SLEEP, vcpu))
 			kvm_vcpu_sleep(vcpu);
 
+		if (kvm_check_request(KVM_REQ_SUSPEND, vcpu))
+			kvm_vcpu_suspend(vcpu);
+
 		if (kvm_check_request(KVM_REQ_VCPU_RESET, vcpu))
 			kvm_reset_vcpu(vcpu);
 
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 275a27368a04..5e5ef9ff4fba 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -95,8 +95,7 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu)
 	} else {
 		trace_kvm_wfx_arm64(*vcpu_pc(vcpu), false);
 		vcpu->stat.wfi_exit_stat++;
-		kvm_vcpu_block(vcpu);
-		kvm_clear_request(KVM_REQ_UNHALT, vcpu);
+		kvm_make_request(KVM_REQ_SUSPEND, vcpu);
 	}
 
 	kvm_incr_pc(vcpu);
diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
index bb59b692998b..d453666ddb83 100644
--- a/arch/arm64/kvm/psci.c
+++ b/arch/arm64/kvm/psci.c
@@ -46,9 +46,7 @@ static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu)
 	 * specification (ARM DEN 0022A). This means all suspend states
 	 * for KVM will preserve the register state.
 	 */
-	kvm_vcpu_block(vcpu);
-	kvm_clear_request(KVM_REQ_UNHALT, vcpu);
-
+	kvm_make_request(KVM_REQ_SUSPEND, vcpu);
 	return PSCI_RET_SUCCESS;
 }
 
-- 
2.33.0.685.g46640cef36-goog

