linux-kernel - [PATCH] LoongArch: KVM: Add PTW feature detection on 3C6000 host

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Message-Id: <20250826033514.972480-1-maobibo@loongson.cn>
Date: Tue, 26 Aug 2025 11:35:14 +0800
From: Bibo Mao <maobibo@...ngson.cn>
To: Tianrui Zhao <zhaotianrui@...ngson.cn>,
	Huacai Chen <chenhuacai@...nel.org>
Cc: WANG Xuerui <kernel@...0n.name>,
	kvm@...r.kernel.org,
	loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH] LoongArch: KVM: Add PTW feature detection on 3C6000 host

With 3C6000 hardware platform, hardware page table walking(PTW) features
is supported on host. Here add this feature detection on KVM host.

Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
---
 arch/loongarch/include/uapi/asm/kvm.h | 1 +
 arch/loongarch/kvm/vcpu.c             | 2 ++
 arch/loongarch/kvm/vm.c               | 4 ++++
 3 files changed, 7 insertions(+)

diff --git a/arch/loongarch/include/uapi/asm/kvm.h b/arch/loongarch/include/uapi/asm/kvm.h
index 5f354f5c6847..57ba1a563bb1 100644
--- a/arch/loongarch/include/uapi/asm/kvm.h
+++ b/arch/loongarch/include/uapi/asm/kvm.h
@@ -103,6 +103,7 @@ struct kvm_fpu {
 #define  KVM_LOONGARCH_VM_FEAT_PMU		5
 #define  KVM_LOONGARCH_VM_FEAT_PV_IPI		6
 #define  KVM_LOONGARCH_VM_FEAT_PV_STEALTIME	7
+#define  KVM_LOONGARCH_VM_FEAT_PTW		8
 
 /* Device Control API on vcpu fd */
 #define KVM_LOONGARCH_VCPU_CPUCFG	0
diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
index ce478151466c..9c802f7103c6 100644
--- a/arch/loongarch/kvm/vcpu.c
+++ b/arch/loongarch/kvm/vcpu.c
@@ -680,6 +680,8 @@ static int _kvm_get_cpucfg_mask(int id, u64 *v)
 			*v |= CPUCFG2_ARMBT;
 		if (cpu_has_lbt_mips)
 			*v |= CPUCFG2_MIPSBT;
+		if (cpu_has_ptw)
+			*v |= CPUCFG2_PTW;
 
 		return 0;
 	case LOONGARCH_CPUCFG3:
diff --git a/arch/loongarch/kvm/vm.c b/arch/loongarch/kvm/vm.c
index edccfc8c9cd8..a49b1c1a3dd1 100644
--- a/arch/loongarch/kvm/vm.c
+++ b/arch/loongarch/kvm/vm.c
@@ -146,6 +146,10 @@ static int kvm_vm_feature_has_attr(struct kvm *kvm, struct kvm_device_attr *attr
 		if (kvm_pvtime_supported())
 			return 0;
 		return -ENXIO;
+	case KVM_LOONGARCH_VM_FEAT_PTW:
+		if (cpu_has_ptw)
+			return 0;
+		return -ENXIO;
 	default:
 		return -ENXIO;
 	}
-- 
2.39.3