[PATCH v6 07/49] KVM: arm64: gic-v5: Cache host IRS ID registers

[Sascha Bischoff <Sascha.Bischoff@arm.com>]

KVM needs access to the host IRS configuration frame to configure
virtual-machine resources. The frame ID registers describe the
capabilities available to KVM.

Cache IRS_IDR2, IRS_IDR3, and IRS_IDR4 rather than extracting their
individual fields into kvm_vgic_global_state. Accessor helpers derive
the required capabilities from the cached registers.

Use the cached IRS_IDR4 VPE capacity to limit the maximum number of
vCPUs, while retaining VGIC_V5_MAX_CPUS as KVM's own upper bound.

Keeping the raw register values lets KVM adjust the exposed
capabilities when needed, as is done for ICH_VTR_EL2, and avoids tying
future EL2 code to the layout of kvm_vgic_global_state.

Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
---
 arch/arm64/kvm/vgic/vgic-v5.c | 22 +++++++++-
 include/kvm/arm_vgic.h        | 75 +++++++++++++++++++++++++++++++++++
 2 files changed, 95 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-v5.c b/arch/arm64/kvm/vgic/vgic-v5.c
index 4e3e4db24e773..e75a66b3920aa 100644
--- a/arch/arm64/kvm/vgic/vgic-v5.c
+++ b/arch/arm64/kvm/vgic/vgic-v5.c
@@ -11,6 +11,7 @@
 #include "vgic.h"
 
 #define ppi_caps	kvm_vgic_global_state.vgic_v5_ppi_caps
+#define irs_caps	kvm_vgic_global_state.vgic_v5_irs_caps
 
 /*
  * Not all PPIs are guaranteed to be implemented for GICv5. Deterermine which
@@ -34,6 +35,21 @@ static void vgic_v5_get_implemented_ppis(void)
 	__assign_bit(GICV5_ARCH_PPI_PMUIRQ, ppi_caps.impl_ppi_mask, system_supports_pmuv3());
 }
 
+static u32 irs_readl_relaxed(const u32 reg_offset)
+{
+	return readl_relaxed(irs_caps.irs_base + reg_offset);
+}
+
+static void vgic_v5_irs_cache_id_regs(const struct gic_kvm_info *info)
+{
+	irs_caps.irs_base = info->gicv5_irs.base;
+	irs_caps.non_coherent = info->gicv5_irs.non_coherent;
+
+	irs_caps.idr2 = irs_readl_relaxed(GICV5_IRS_IDR2);
+	irs_caps.idr3 = irs_readl_relaxed(GICV5_IRS_IDR3);
+	irs_caps.idr4 = irs_readl_relaxed(GICV5_IRS_IDR4);
+}
+
 /*
  * Probe for a vGICv5 compatible interrupt controller, returning 0 on success.
  */
@@ -60,10 +76,12 @@ int vgic_v5_probe(const struct gic_kvm_info *info)
 		goto skip_v5;
 	}
 
-	kvm_vgic_global_state.max_gic_vcpus = VGIC_V5_MAX_CPUS;
-
+	vgic_v5_irs_cache_id_regs(info);
 	vgic_v5_get_implemented_ppis();
 
+	kvm_vgic_global_state.max_gic_vcpus = min(vgic_v5_irs_max_vpes(&irs_caps),
+						  VGIC_V5_MAX_CPUS);
+
 	ret = kvm_register_vgic_device(KVM_DEV_TYPE_ARM_VGIC_V5);
 	if (ret) {
 		kvm_err("Cannot register GICv5 KVM device.\n");
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 086b7578e5f33..c82aa7c9e3f32 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -132,6 +132,19 @@ enum vgic_type {
 	VGIC_V5,		/* Newer, fancier GICv5 */
 };
 
+struct vgic_v5_irs_caps {
+	/* Base address of the host IRS's CONFIG_FRAME */
+	void __iomem	*irs_base;
+
+	/* Raw host IRS ID registers */
+	u32		idr2;
+	u32		idr3;
+	u32		idr4;
+
+	/* Is the IRS coherent with us, or not? */
+	bool		non_coherent;
+};
+
 /* same for all guests, as depending only on the _host's_ GIC model */
 struct vgic_global {
 	/* type of the host GIC */
@@ -182,6 +195,9 @@ struct vgic_global {
 	struct {
 		DECLARE_BITMAP(impl_ppi_mask, VGIC_V5_NR_PRIVATE_IRQS);
 	} vgic_v5_ppi_caps;
+
+	/* GICv5 IRS capabilities */
+	struct vgic_v5_irs_caps vgic_v5_irs_caps;
 };
 
 extern struct vgic_global kvm_vgic_global_state;
@@ -627,6 +643,65 @@ int vgic_v4_load(struct kvm_vcpu *vcpu);
 void vgic_v4_commit(struct kvm_vcpu *vcpu);
 int vgic_v4_put(struct kvm_vcpu *vcpu);
 
+static inline u8 vgic_v5_irs_ist_id_bits(const struct vgic_v5_irs_caps *caps)
+{
+	return FIELD_GET(GICV5_IRS_IDR2_ID_BITS, caps->idr2);
+}
+
+static inline u8 vgic_v5_irs_min_lpi_id_bits(const struct vgic_v5_irs_caps *caps)
+{
+	return FIELD_GET(GICV5_IRS_IDR2_MIN_LPI_ID_BITS, caps->idr2);
+}
+
+static inline bool vgic_v5_irs_ist_levels(const struct vgic_v5_irs_caps *caps)
+{
+	return !!(caps->idr2 & GICV5_IRS_IDR2_IST_LEVELS);
+}
+
+static inline u8 vgic_v5_irs_ist_l2sz(const struct vgic_v5_irs_caps *caps)
+{
+	return FIELD_GET(GICV5_IRS_IDR2_IST_L2SZ, caps->idr2);
+}
+
+static inline bool vgic_v5_irs_istmd(const struct vgic_v5_irs_caps *caps)
+{
+	return !!(caps->idr2 & GICV5_IRS_IDR2_ISTMD);
+}
+
+static inline u8 vgic_v5_irs_istmd_sz(const struct vgic_v5_irs_caps *caps)
+{
+	return FIELD_GET(GICV5_IRS_IDR2_ISTMD_SZ, caps->idr2);
+}
+
+static inline u32 vgic_v5_irs_max_vms(const struct vgic_v5_irs_caps *caps)
+{
+	return BIT(FIELD_GET(GICV5_IRS_IDR3_VM_ID_BITS, caps->idr3));
+}
+
+static inline bool vgic_v5_irs_two_level_vmt_support(const struct vgic_v5_irs_caps *caps)
+{
+	return !!(caps->idr3 & GICV5_IRS_IDR3_VMT_LEVELS);
+}
+
+static inline u16 vgic_v5_irs_vmd_size(const struct vgic_v5_irs_caps *caps)
+{
+	if (!(caps->idr3 & GICV5_IRS_IDR3_VMD))
+		return 0;
+
+	return BIT(FIELD_GET(GICV5_IRS_IDR3_VMD_SZ, caps->idr3));
+}
+
+static inline u16 vgic_v5_irs_vped_size(const struct vgic_v5_irs_caps *caps)
+{
+	return BIT(FIELD_GET(GICV5_IRS_IDR4_VPED_SZ, caps->idr4));
+}
+
+static inline u32 vgic_v5_irs_max_vpes(const struct vgic_v5_irs_caps *caps)
+{
+	/* Field stores VPE_ID_BITS - 1 */
+	return BIT(FIELD_GET(GICV5_IRS_IDR4_VPE_ID_BITS, caps->idr4) + 1);
+}
+
 int vgic_v5_finalize_ppi_state(struct kvm *kvm);
 bool vgic_v5_ppi_queue_irq_unlock(struct kvm *kvm, struct vgic_irq *irq,
 				  unsigned long flags);
-- 
2.34.1