KVM: arm64: vgic-v3: Simplify initial GICv3 configuration sampling

Now that we have our magic inline helper for ICH_VTR_EL2, we can
get rid of the hack that was reporting a combination of that
register and of the indication of the CPU interface supporting
GICv2 compatibility. We now only report the latter.

As a small benefit, GICv5 is not involved in this stuff anymore,
since it never has GICv2 compatibility..

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://patch.msgid.link/20260721170754.3150521-6-maz@kernel.org
Signed-off-by: Oliver Upton <oupton@kernel.org>

4 files changed, 8 insertions, 28 deletions

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 043495f7fc78..cb354a037fc5 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -281,7 +281,7 @@ extern int __kvm_vcpu_run(struct kvm_vcpu *vcpu);
 
 extern void __kvm_adjust_pc(struct kvm_vcpu *vcpu);
 
-extern u64 __vgic_v3_get_gic_config(void);
+extern bool __vgic_v3_get_gic_config(void);
 extern void __vgic_v3_init_lrs(void);
 
 #define __KVM_EXTABLE(from, to)						\
diff --git a/arch/arm64/kvm/hyp/vgic-v3-sr.c b/arch/arm64/kvm/hyp/vgic-v3-sr.c
index 3e5d5ddf35a1..74d4a509f1de 100644
--- a/arch/arm64/kvm/hyp/vgic-v3-sr.c
+++ b/arch/arm64/kvm/hyp/vgic-v3-sr.c
@@ -437,26 +437,12 @@ void __vgic_v3_init_lrs(void)
 		__gic_v3_set_lr(0, i);
 }
 
-/*
- * Return the GIC CPU configuration:
- * - [31:0]  ICH_VTR_EL2
- * - [62:32] RES0
- * - [63]    MMIO (GICv2) capable
- */
-u64 __vgic_v3_get_gic_config(void)
+/* Return true if GICv3 is MMIO (GICv2) capable, false otherwise */
+bool __vgic_v3_get_gic_config(void)
 {
 	u64 val, sre;
 	unsigned long flags = 0;
 
-	/*
-	 * In compat mode, we cannot access ICC_SRE_EL1 at any EL
-	 * other than EL1 itself; just return the
-	 * ICH_VTR_EL2. ICC_IDR0_EL1 is only implemented on a GICv5
-	 * system, so we first check if we have GICv5 support.
-	 */
-	if (cpus_have_final_cap(ARM64_HAS_GICV5_CPUIF))
-		return vgic_ich_vtr();
-
 	sre = read_gicreg(ICC_SRE_EL1);
 	/*
 	 * To check whether we have a MMIO-based (GICv2 compatible)
@@ -497,10 +483,7 @@ u64 __vgic_v3_get_gic_config(void)
 		isb();
 	}
 
-	val  = (val & ICC_SRE_EL1_SRE) ? 0 : (1ULL << 63);
-	val |= vgic_ich_vtr();
-
-	return val;
+	return !(val & ICC_SRE_EL1_SRE);
 }
 
 static void __vgic_v3_compat_mode_enable(void)
diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
index 098187e34c58..734fa3138723 100644
--- a/arch/arm64/kvm/vgic/vgic-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-v3.c
@@ -936,12 +936,12 @@ void vgic_v3_enable_cpuif_traps(void)
  */
 int vgic_v3_probe(const struct gic_kvm_info *info)
 {
-	u64 ich_vtr_el2 = kvm_call_hyp_ret(__vgic_v3_get_gic_config);
+	u64 ich_vtr_el2;
 	bool has_v2;
 	int ret;
 
-	has_v2 = ich_vtr_el2 >> 63;
-	ich_vtr_el2 = (u32)ich_vtr_el2;
+	has_v2 = kvm_call_hyp_ret(__vgic_v3_get_gic_config);
+	ich_vtr_el2 = vgic_ich_vtr();
 
 	/*
 	 * The ListRegs field is 5 bits, but there is an architectural
@@ -996,9 +996,6 @@ int vgic_v3_probe(const struct gic_kvm_info *info)
 	if (has_v2)
 		static_branch_enable(&vgic_v3_has_v2_compat);
 
-	if (vgic_v3_broken_seis())
-		kvm_vgic_global_state.ich_vtr_el2 &= ~ICH_VTR_EL2_SEIS;
-
 	vgic_v3_enable_cpuif_traps();
 
 	kvm_vgic_global_state.vctrl_base = NULL;
diff --git a/arch/arm64/kvm/vgic/vgic-v5.c b/arch/arm64/kvm/vgic/vgic-v5.c
index d4789ff3e740..16bc0a670d3e 100644
--- a/arch/arm64/kvm/vgic/vgic-v5.c
+++ b/arch/arm64/kvm/vgic/vgic-v5.c
@@ -83,7 +83,7 @@ skip_v5:
 	}
 
 	kvm_vgic_global_state.has_gcie_v3_compat = true;
-	ich_vtr_el2 =  kvm_call_hyp_ret(__vgic_v3_get_gic_config);
+	ich_vtr_el2 = vgic_ich_vtr();
 	kvm_vgic_global_state.ich_vtr_el2 = (u32)ich_vtr_el2;
 
 	/*