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From: Marc Zyngier <maz@kernel.org>
To: linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
	kvmarm@lists.cs.columbia.edu
Cc: James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Eric Auger <eric.auger@redhat.com>,
	Hector Martin <marcan@marcan.st>,
	Mark Rutland <mark.rutland@arm.com>,
	kernel-team@android.com
Subject: [PATCH v2 4/9] KVM: arm64: vgic: Let an interrupt controller advertise lack of HW deactivation
Date: Sat,  3 Apr 2021 12:29:26 +0100
Message-ID: <20210403112931.1043452-5-maz@kernel.org> (raw)
In-Reply-To: <20210403112931.1043452-1-maz@kernel.org>

The vGIC, as architected by ARM, allows a virtual interrupt to
trigger the deactivation of a physical interrupt. This allows
the following interrupt to be delivered without requiring an exit.

However, some implementations have choosen not to implement this,
meaning that we will need some unsavoury workarounds to deal with this.

On detecting such a case, taint the kernel and spit a nastygram.
We'll deal with this in later patches.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/vgic/vgic-init.c       | 10 ++++++++++
 include/kvm/arm_vgic.h                |  3 +++
 include/linux/irqchip/arm-vgic-info.h |  2 ++
 3 files changed, 15 insertions(+)

diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c
index 00c75495fd0c..0c8637a58535 100644
--- a/arch/arm64/kvm/vgic/vgic-init.c
+++ b/arch/arm64/kvm/vgic/vgic-init.c
@@ -521,6 +521,16 @@ int kvm_vgic_hyp_init(void)
 	if (!gic_kvm_info)
 		return -ENODEV;
 
+	/*
+	 * If we get one of these oddball non-GICs, taint the kernel,
+	 * as we have no idea of how they *really* behave.
+	 */
+	if (gic_kvm_info->no_hw_deactivation) {
+		kvm_info("Non-architectural vgic, tainting kernel\n");
+		add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);
+		kvm_vgic_global_state.no_hw_deactivation = true;
+	}
+
 	switch (gic_kvm_info->type) {
 	case GIC_V2:
 		ret = vgic_v2_probe(gic_kvm_info);
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 3d74f1060bd1..7afe789194d8 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -72,6 +72,9 @@ struct vgic_global {
 	bool			has_gicv4;
 	bool			has_gicv4_1;
 
+	/* Pseudo GICv3 from outer space */
+	bool			no_hw_deactivation;
+
 	/* GIC system register CPU interface */
 	struct static_key_false gicv3_cpuif;
 
diff --git a/include/linux/irqchip/arm-vgic-info.h b/include/linux/irqchip/arm-vgic-info.h
index 0319636be928..d39d0b591c5a 100644
--- a/include/linux/irqchip/arm-vgic-info.h
+++ b/include/linux/irqchip/arm-vgic-info.h
@@ -30,6 +30,8 @@ struct gic_kvm_info {
 	bool		has_v4;
 	/* rvpeid support */
 	bool		has_v4_1;
+	/* Deactivation impared, subpar stuff */
+	bool		no_hw_deactivation;
 };
 
 #ifdef CONFIG_KVM
-- 
2.29.2


  parent reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-03 11:29 [PATCH v2 0/9] KVM: arm64: Initial host support for the Apple M1 Marc Zyngier
2021-04-03 11:29 ` [PATCH v2 1/9] irqchip/gic: Split vGIC probing information from the GIC code Marc Zyngier
2021-04-03 11:29 ` [PATCH v2 2/9] KVM: arm64: Handle physical FIQ as an IRQ while running a guest Marc Zyngier
2021-04-03 11:29 ` [PATCH v2 3/9] KVM: arm64: vgic: Be tolerant to the lack of maintenance interrupt Marc Zyngier
2021-04-03 11:29 ` Marc Zyngier [this message]
2021-04-03 11:29 ` [PATCH v2 5/9] KVM: arm64: vgic: move irq->get_input_level into an ops structure Marc Zyngier
2021-04-03 11:29 ` [PATCH v2 6/9] KVM: arm64: vgic: Implement SW-driven deactivation Marc Zyngier
2021-04-03 11:29 ` [PATCH v2 7/9] KVM: arm64: timer: Refactor IRQ configuration Marc Zyngier
2021-04-03 11:29 ` [PATCH v2 8/9] KVM: arm64: timer: Add support for SW-based deactivation Marc Zyngier
2021-04-03 11:29 ` [PATCH v2 9/9] irqchip/apple-aic: Advertise some level of vGICv3 compatibility Marc Zyngier

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