linux-kernel - [RFC PATCH 31/34] gunyah: allow userspace to set boot cpu context

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Message-Id: <20250424141341.841734-32-karim.manaouil@linaro.org>
Date: Thu, 24 Apr 2025 15:13:38 +0100
From: Karim Manaouil <karim.manaouil@...aro.org>
To: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org,
	linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev
Cc: Karim Manaouil <karim.manaouil@...aro.org>,
	Alexander Graf <graf@...zon.com>,
	Alex Elder <elder@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Fuad Tabba <tabba@...gle.com>,
	Joey Gouly <joey.gouly@....com>,
	Jonathan Corbet <corbet@....net>,
	Marc Zyngier <maz@...nel.org>,
	Mark Brown <broonie@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>,
	Quentin Perret <qperret@...gle.com>,
	Rob Herring <robh@...nel.org>,
	Srinivas Kandagatla <srini@...nel.org>,
	Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
	Will Deacon <will@...nel.org>,
	Haripranesh S <haripran@....qualcomm.com>,
	Carl van Schaik <cvanscha@....qualcomm.com>,
	Murali Nalajala <mnalajal@...cinc.com>,
	Sreenivasulu Chalamcharla <sreeniva@....qualcomm.com>,
	Trilok Soni <tsoni@...cinc.com>,
	Stefan Schmidt <stefan.schmidt@...aro.org>
Subject: [RFC PATCH 31/34] gunyah: allow userspace to set boot cpu context

Allow userspace hypervisor (e.g. Qemu) to set the context of the boot
cpu. At the moment, only the program counter (PC) is needed.

Signed-off-by: Karim Manaouil <karim.manaouil@...aro.org>
---
 arch/arm64/kvm/gunyah.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/arch/arm64/kvm/gunyah.c b/arch/arm64/kvm/gunyah.c
index e8037d636e8f..df922be2429e 100644
--- a/arch/arm64/kvm/gunyah.c
+++ b/arch/arm64/kvm/gunyah.c
@@ -1703,6 +1703,24 @@ static int gunyah_vm_rm_notification(struct notifier_block *nb,
 	}
 }
 
+/*
+ * We only need to set PC to start of kernel
+ */
+static int gunyah_vm_set_boot_ctx(struct gunyah_vm *ghvm)
+{
+	struct kvm_vcpu *vcpu = kvm_get_vcpu(&ghvm->kvm, 0);
+	u64 core_reg = KVM_REG_ARM64 | KVM_REG_SIZE_U64 | KVM_REG_ARM_CORE;
+	struct kvm_one_reg reg;
+	u64 *regaddr;
+
+	reg.id = core_reg | KVM_REG_ARM_CORE_REG(regs.pc);
+	regaddr = core_reg_addr(vcpu, &reg);
+
+	/* We only need to set PC atm. regset is 1 */
+	return gunyah_rm_vm_set_boot_context(
+			ghvm->rm, ghvm->vmid, 1, 0, *regaddr);
+}
+
 static void gunyah_vm_stop(struct gunyah_vm *ghvm)
 {
 	int ret;
@@ -1790,6 +1808,12 @@ static int gunyah_vm_start(struct gunyah_vm *ghvm)
 	}
 	ghvm->vm_status = GUNYAH_RM_VM_STATUS_READY;
 
+	ret = gunyah_vm_set_boot_ctx(ghvm);
+	if (ret) {
+		pr_warn("Failed to setup boot context: %d\n", ret);
+		goto err;
+	}
+
 	ret = gunyah_rm_get_hyp_resources(ghvm->rm, ghvm->vmid, &resources);
 	if (ret) {
 		pr_warn("Failed to get hyp resources for VM: %d\n", ret);
-- 
2.39.5