Subject: [PATCH v1 16/26] KVM: s390: arm64: Add sysreg related functions and definitions

From: Steffen Eiden <[email-masked]>
Date: Fri, 29 May 2026 17:55:49 +0200

Add guest sysreg access macros in asm/kvm_host_arm64.h using
easr()/sasr()-based helpers for sysregs that map to the SAE save area.

Also add the guest-visible sysreg enum and per-vCPU/per-VM storage for
state that is not directly covered by the save area, such as CLIDR_EL1,
CSSELR_EL1, MPIDR_EL1, and VM-wide ID register state.

This lays out the header-side definitions needed to ensure compilation
success during for the share-code-patches and later sysreg handling
during vCPU setup and runtime.

Signed-off-by: Steffen Eiden <[email-masked]>
---
 arch/s390/include/asm/kvm_host_arm64.h | 165 +++++++++++++++++++++++++
 1 file changed, 165 insertions(+)

diff --git a/arch/s390/include/asm/kvm_host_arm64.h b/arch/s390/include/asm/kvm_host_arm64.h
index 8c3214c5b004..d6d9e3ad7a8e 100644
--- a/arch/s390/include/asm/kvm_host_arm64.h
+++ b/arch/s390/include/asm/kvm_host_arm64.h
@@ -44,10 +44,19 @@ struct kvm_vcpu_arch {
 	struct kvm_sae_save_area save_area;
 	struct kvm_cpu_context ctxt;
 
+	/* Guest system registers not part of save area or ID registers */
+	u64 sys_reg_clidr_el1;
+	u64 sys_reg_csselr_el1;
+	/* Per-vcpu CCSIDR override or NULL */
+	u32 *ccsidr;
+
 	u32 host_acrs[NUM_ACRS];
 
 	/* Hypervisor Configuration Register */
 	u64 hcr_elz;
+	u64 hcrx_elz;
+
+	u64 mpidr;
 
 	/* Configuration flags, set once and for all before the vcpu can run */
 	u8 cflags;
@@ -209,4 +218,160 @@ static inline void kvm_arch_async_page_present_queued(struct kvm_vcpu *vcpu)
 
 #define kvm_supports_32bit_el0() false
 
+#define vcpu_read_sys_reg(_v, _r) 0xbad1234bad
+#define vcpu_write_sys_reg(_v, _p, _r) ((void)0)
+
+#define __vcpu_sys_reg(__vcpu, __reg) \
+	vcpu_read_sys_reg(__vcpu, __reg)
+
+#define __vcpu_assign_sys_reg(__vcpu, __reg, __val) \
+	vcpu_write_sys_reg(__vcpu, __val, __reg)
+
+/* Read, modify and write system register
+ *
+ */
+#define _vcpu_rmw_sys_reg(C, V, OP, R) \
+({ \
+	u64 __val = vcpu_read_sys_reg(C, R); \
+	__val OP V; \
+	vcpu_write_sys_reg(C, __val, R); \
+})
+
+/**
+ * _vcpu_read_sys_reg() - read a guest sysreg with easr
+ * - R - sysreg id; must be readable by easr; must be compile time constant
+ *
+ *   if SYSREGS_ON_CPU: proceed with flags = 0
+ *   otherwise:         proceed with either
+ *                         read:  flags = EASR_FLAG_SA
+ *                         write: flags = SASR_FLAG_INITIALIZED
+ *
+ */
+#define _vcpu_read_sys_reg(C, R) \
+	({	BUILD_BUG_ON(!__builtin_constant_p((R))); \
+		BUG_ON(vcpu_is_loaded(C) && smp_processor_id() != (C)->cpu); \
+		(vcpu_is_loaded(C)) \
+			? __vcpu_read_sr((C), (R), 0) \
+			: __vcpu_read_sr((C), (R), EASR_FLAG_SA); })
+
+/**
+ * _vcpu_write_sys_reg() - write a guest sysreg with sasr
+ * - R - sysreg id; must be readable by sasr; must be compile time constant
+
+ *   if SYSREGS_ON_CPU: proceed with flags = 0
+ *   otherwise:         proceed with either
+ *                         read:  flags = EASR_FLAG_SA
+ *                         write: flags = SASR_FLAG_INITIALIZED
+ */
+#define _vcpu_write_sys_reg(C, V, R) \
+	({	BUILD_BUG_ON(!__builtin_constant_p((R))); \
+		BUG_ON(vcpu_is_loaded(C) && smp_processor_id() != (C)->cpu); \
+		(vcpu_is_loaded(C)) \
+			? __vcpu_write_sr((C), (V), (R), 0) \
+			: __vcpu_write_sr((C), (V), (R), SASR_FLAG_INITIALIZED); })
+
+/* Forward to easr / sasr
+ * assert that F and R are constant
+ */
+#define __vcpu_read_sr(C, R, F) \
+	({	BUILD_BUG_ON(!__builtin_constant_p((R))); \
+		BUILD_BUG_ON(!__builtin_constant_p((F))); \
+		easr((R), &(C)->arch.save_area, (F)); })
+
+#define __vcpu_write_sr(C, V, R, F) \
+	({	BUILD_BUG_ON(!__builtin_constant_p((R))); \
+		BUILD_BUG_ON(!__builtin_constant_p((F))); \
+		sasr((R), (V), &(C)->arch.save_area, (F)); })
+
+#define SR_GROUP(NAME, ...)	\
+	__##NAME##_BEGIN__,	\
+	__VA_ARGS__		\
+	__##NAME##_END__
+
+/** enum vcpu_sysreg - available guest sysregs
+ *
+ * Contains all arm64 guest-syregs supported by s390.
+ */
+enum vcpu_sysreg {
+	__INVALID_SYSREG__, /* 0 is reserved as an invalid value */
+
+	/* EL 0,1 Register from state description in order of appearance */
+	SR_GROUP(STATE_DESC,
+	CNTP_CTL_EL0,
+	CNTV_CTL_EL0,
+	CONTEXTIDR_EL1,
+	SP_EL1,
+	),
+
+	/* EL 0,1 Register requiring special handling. */
+	SR_GROUP(SPECIAL,
+	CSSELR_EL1,
+	CLIDR_EL1,
+	MPIDR_EL1,
+	),
+
+	/* EL 0,1 register from save area in order of appearance */
+	SR_GROUP(SAVE_AREA,
+	ACTLR_EL1,
+	AFSR0_EL1,
+	AFSR1_EL1,
+	CNTFRQ_EL0,
+	CNTP_CVAL_EL0,
+	CNTV_CVAL_EL0,
+	DISR_EL1,
+	MIDR_EL1,
+	OSLSR_EL1,
+	PAR_EL1,
+	OSLAR_EL1,
+	SCTLR_EL1,
+	CPACR_EL1,
+	VBAR_EL1,
+	SPSR_EL1,
+	ELR_EL1,
+	ESR_EL1,
+	TCR_EL1,
+	MAIR_EL1,
+	TTBR0_EL1,
+	TTBR1_EL1,
+	FAR_EL1,
+	TPIDR_EL0,
+	TPIDR_EL1,
+	TPIDRRO_EL0,
+	CNTKCTL_EL1,
+	ZCR_EL1,
+	SCXTNUM_EL0,
+	SCXTNUM_EL1,
+	APIBKEYLO_EL1,
+	APIBKEYHI_EL1,
+	APIAKEYLO_EL1,
+	APIAKEYHI_EL1,
+	APGAKEYLO_EL1,
+	APGAKEYHI_EL1,
+	APDBKEYLO_EL1,
+	APDBKEYHI_EL1,
+	APDAKEYLO_EL1,
+	APDAKEYHI_EL1,
+	MDSCR_EL1,
+	),
+
+	NR_SYS_REGS /* Nothing after this line! */
+};
+
+void vcpu_write_host_sys_reg(struct kvm_vcpu *vcpu, u64 val, int reg);
+u64 vcpu_read_host_sys_reg(const struct kvm_vcpu *vcpu, int reg);
+
+#define kvm_debug_handle_oslar(_v, _val) /* debug not implemented yet*/
+
+static inline u8 kvm_arm_pmu_get_pmuver_limit(void)
+{
+	return 0;
+}
+
+int __init kvm_sys_reg_table_init(void);
+
+static inline u64 kvm_sanitised_host_ftr_reg(u32 id)
+{
+	return 0xbad1234bad;
+}
+
 #endif /* ASM_KVM_HOST_ARM64_H */
-- 
2.53.0