Merge branch kvm-arm64/gic-v5-nv into kvmarm-master/next

* kvm-arm64/gic-v5-nv:
  : .
  : Add NV support to GICv5 in GICv3 emulation mode, ensuring that the v3
  : guest support is identical to that of a pure v3 platform.
  :
  : Patches courtesy of Sascha Bischoff (20250828105925.3865158-1-sascha.bischoff@arm.com)
  : .
  irqchip/gic-v5: Drop has_gcie_v3_compat from gic_kvm_info
  KVM: arm64: Use ARM64_HAS_GICV5_LEGACY for GICv5 probing
  arm64: cpucaps: Add GICv5 Legacy vCPU interface (GCIE_LEGACY) capability
  KVM: arm64: Enable nested for GICv5 host with FEAT_GCIE_LEGACY
  KVM: arm64: Don't access ICC_SRE_EL2 if GICv3 doesn't support v2 compatibility

Signed-off-by: Marc Zyngier <maz@kernel.org>

10 files changed, 41 insertions, 28 deletions

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index ef269a5a37e1..770a41fa7214 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2539,6 +2539,15 @@ test_has_mpam_hcr(const struct arm64_cpu_capabilities *entry, int scope)
 	return idr & MPAMIDR_EL1_HAS_HCR;
 }
 
+static bool
+test_has_gicv5_legacy(const struct arm64_cpu_capabilities *entry, int scope)
+{
+	if (!this_cpu_has_cap(ARM64_HAS_GICV5_CPUIF))
+		return false;
+
+	return !!(read_sysreg_s(SYS_ICC_IDR0_EL1) & ICC_IDR0_EL1_GCIE_LEGACY);
+}
+
 static const struct arm64_cpu_capabilities arm64_features[] = {
 	{
 		.capability = ARM64_ALWAYS_BOOT,
@@ -3156,6 +3165,12 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.matches = has_cpuid_feature,
 		ARM64_CPUID_FIELDS(ID_AA64PFR2_EL1, GCIE, IMP)
 	},
+	{
+		.desc = "GICv5 Legacy vCPU interface",
+		.type = ARM64_CPUCAP_EARLY_LOCAL_CPU_FEATURE,
+		.capability = ARM64_HAS_GICV5_LEGACY,
+		.matches = test_has_gicv5_legacy,
+	},
 	{},
 };
 
diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
index 714b0b5ec5ac..5369763606e7 100644
--- a/arch/arm64/kernel/image-vars.h
+++ b/arch/arm64/kernel/image-vars.h
@@ -105,6 +105,9 @@ KVM_NVHE_ALIAS(__hyp_stub_vectors);
 KVM_NVHE_ALIAS(vgic_v2_cpuif_trap);
 KVM_NVHE_ALIAS(vgic_v3_cpuif_trap);
 
+/* Static key indicating whether GICv3 has GICv2 compatibility */
+KVM_NVHE_ALIAS(vgic_v3_has_v2_compat);
+
 /* Static key which is set if CNTVOFF_EL2 is unusable */
 KVM_NVHE_ALIAS(broken_cntvoff_key);
 
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index b77ebe3aafb5..a59b4046617c 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -2321,8 +2321,9 @@ static int __init init_subsystems(void)
 	}
 
 	if (kvm_mode == KVM_MODE_NV &&
-	   !(vgic_present && kvm_vgic_global_state.type == VGIC_V3)) {
-		kvm_err("NV support requires GICv3, giving up\n");
+		!(vgic_present && (kvm_vgic_global_state.type == VGIC_V3 ||
+				   kvm_vgic_global_state.has_gcie_v3_compat))) {
+		kvm_err("NV support requires GICv3 or GICv5 with legacy support, giving up\n");
 		err = -EINVAL;
 		goto out;
 	}
diff --git a/arch/arm64/kvm/hyp/vgic-v3-sr.c b/arch/arm64/kvm/hyp/vgic-v3-sr.c
index d81275790e69..acd909b7f225 100644
--- a/arch/arm64/kvm/hyp/vgic-v3-sr.c
+++ b/arch/arm64/kvm/hyp/vgic-v3-sr.c
@@ -295,12 +295,8 @@ void __vgic_v3_activate_traps(struct vgic_v3_cpu_if *cpu_if)
 		}
 	}
 
-	/*
-	 * GICv5 BET0 FEAT_GCIE_LEGACY doesn't include ICC_SRE_EL2. This is due
-	 * to be relaxed in a future spec release, at which point this in
-	 * condition can be dropped.
-	 */
-	if (!cpus_have_final_cap(ARM64_HAS_GICV5_CPUIF)) {
+	/* Only disable SRE if the host implements the GICv2 interface */
+	if (static_branch_unlikely(&vgic_v3_has_v2_compat)) {
 		/*
 		 * Prevent the guest from touching the ICC_SRE_EL1 system
 		 * register. Note that this may not have any effect, as
@@ -329,19 +325,16 @@ void __vgic_v3_deactivate_traps(struct vgic_v3_cpu_if *cpu_if)
 		cpu_if->vgic_vmcr = read_gicreg(ICH_VMCR_EL2);
 	}
 
-	/*
-	 * Can be dropped in the future when GICv5 spec is relaxed. See comment
-	 * above.
-	 */
-	if (!cpus_have_final_cap(ARM64_HAS_GICV5_CPUIF)) {
+	/* Only restore SRE if the host implements the GICv2 interface */
+	if (static_branch_unlikely(&vgic_v3_has_v2_compat)) {
 		val = read_gicreg(ICC_SRE_EL2);
 		write_gicreg(val | ICC_SRE_EL2_ENABLE, ICC_SRE_EL2);
-	}
 
-	if (!cpu_if->vgic_sre) {
-		/* Make sure ENABLE is set at EL2 before setting SRE at EL1 */
-		isb();
-		write_gicreg(1, ICC_SRE_EL1);
+		if (!cpu_if->vgic_sre) {
+			/* Make sure ENABLE is set at EL2 before setting SRE at EL1 */
+			isb();
+			write_gicreg(1, ICC_SRE_EL1);
+		}
 	}
 
 	/*
diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
index b9ad7c42c5b0..f1c153106c56 100644
--- a/arch/arm64/kvm/vgic/vgic-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-v3.c
@@ -588,6 +588,7 @@ int vgic_v3_map_resources(struct kvm *kvm)
 }
 
 DEFINE_STATIC_KEY_FALSE(vgic_v3_cpuif_trap);
+DEFINE_STATIC_KEY_FALSE(vgic_v3_has_v2_compat);
 
 static int __init early_group0_trap_cfg(char *buf)
 {
@@ -697,6 +698,13 @@ int vgic_v3_probe(const struct gic_kvm_info *info)
 	if (kvm_vgic_global_state.vcpu_base == 0)
 		kvm_info("disabling GICv2 emulation\n");
 
+	/*
+	 * Flip the static branch if the HW supports v2, even if we're
+	 * not using it (such as in protected mode).
+	 */
+	if (has_v2)
+		static_branch_enable(&vgic_v3_has_v2_compat);
+
 	if (cpus_have_final_cap(ARM64_WORKAROUND_CAVIUM_30115)) {
 		group0_trap = true;
 		group1_trap = true;
diff --git a/arch/arm64/kvm/vgic/vgic-v5.c b/arch/arm64/kvm/vgic/vgic-v5.c
index 6bdbb221bcde..2d3811f4e117 100644
--- a/arch/arm64/kvm/vgic/vgic-v5.c
+++ b/arch/arm64/kvm/vgic/vgic-v5.c
@@ -15,7 +15,7 @@ int vgic_v5_probe(const struct gic_kvm_info *info)
 	u64 ich_vtr_el2;
 	int ret;
 
-	if (!info->has_gcie_v3_compat)
+	if (!cpus_have_final_cap(ARM64_HAS_GICV5_LEGACY))
 		return -ENODEV;
 
 	kvm_vgic_global_state.type = VGIC_V5;
diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index 9ff5cdbd2759..1b32c1232d28 100644
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -37,6 +37,7 @@ HAS_GENERIC_AUTH_ARCH_QARMA5
 HAS_GENERIC_AUTH_IMP_DEF
 HAS_GICV3_CPUIF
 HAS_GICV5_CPUIF
+HAS_GICV5_LEGACY
 HAS_GIC_PRIO_MASKING
 HAS_GIC_PRIO_RELAXED_SYNC
 HAS_HCR_NV1
diff --git a/drivers/irqchip/irq-gic-v5.c b/drivers/irqchip/irq-gic-v5.c
index 4bd224f359a7..41ef286c4d78 100644
--- a/drivers/irqchip/irq-gic-v5.c
+++ b/drivers/irqchip/irq-gic-v5.c
@@ -1062,16 +1062,9 @@ static void gicv5_set_cpuif_idbits(void)
 #ifdef CONFIG_KVM
 static struct gic_kvm_info gic_v5_kvm_info __initdata;
 
-static bool __init gicv5_cpuif_has_gcie_legacy(void)
-{
-	u64 idr0 = read_sysreg_s(SYS_ICC_IDR0_EL1);
-	return !!FIELD_GET(ICC_IDR0_EL1_GCIE_LEGACY, idr0);
-}
-
 static void __init gic_of_setup_kvm_info(struct device_node *node)
 {
 	gic_v5_kvm_info.type = GIC_V5;
-	gic_v5_kvm_info.has_gcie_v3_compat = gicv5_cpuif_has_gcie_legacy();
 
 	/* GIC Virtual CPU interface maintenance interrupt */
 	gic_v5_kvm_info.no_maint_irq_mask = false;
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index e7ffaf4bf2e7..dd9af8a401d3 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -375,6 +375,7 @@ struct vgic_cpu {
 
 extern struct static_key_false vgic_v2_cpuif_trap;
 extern struct static_key_false vgic_v3_cpuif_trap;
+extern struct static_key_false vgic_v3_has_v2_compat;
 
 int kvm_set_legacy_vgic_v2_addr(struct kvm *kvm, struct kvm_arm_device_addr *dev_addr);
 void kvm_vgic_early_init(struct kvm *kvm);
diff --git a/include/linux/irqchip/arm-vgic-info.h b/include/linux/irqchip/arm-vgic-info.h
index ca1713fac6e3..a470a73a805a 100644
--- a/include/linux/irqchip/arm-vgic-info.h
+++ b/include/linux/irqchip/arm-vgic-info.h
@@ -36,8 +36,6 @@ struct gic_kvm_info {
 	bool		has_v4_1;
 	/* Deactivation impared, subpar stuff */
 	bool		no_hw_deactivation;
-	/* v3 compat support (GICv5 hosts, only) */
-	bool		has_gcie_v3_compat;
 };
 
 #ifdef CONFIG_KVM