KVM: arm64: Drop the target_table[] indirection

KVM for 32bit arm had a get/set target mechanism to allow for
micro-architecture differences that are visible in system registers
to be described.

KVM's user-space can query the supported targets for a CPU, and
create vCPUs for that target. The target can override the handling
of system registers to provide different reset or RES0 behaviour.
On 32bit arm this was used to provide different ACTLR reset values
for A7 and A15.

On 64bit arm, the first few CPUs out of the gate used this mechanism,
before it was deemed redundant in commit bca556ac ("arm64/kvm:
Add generic v8 KVM target"). All future CPUs use the
KVM_ARM_TARGET_GENERIC_V8 target.

The 64bit target_table[] stuff exists to preserve the ABI to
user-space. As all targets registers genericv8_target_table, there
is no reason to look the target up.

Until we can merge genericv8_target_table with the main sys_regs
array, kvm_register_target_sys_reg_table() becomes
kvm_check_target_sys_reg_table(), which uses BUG_ON() in keeping
with the other callers in this file.
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200622113317.20477-2-james.morse@arm.com

arch/arm64/include/asm/kvm_coproc.h

@@ -24,8 +24,7 @@ struct kvm_sys_reg_target_table {
 	struct kvm_sys_reg_table table32;
 };
 
-void kvm_register_target_sys_reg_table(unsigned int target,
-				       struct kvm_sys_reg_target_table *table);
+void kvm_check_target_sys_reg_table(struct kvm_sys_reg_target_table *table);
 
 int kvm_handle_cp14_load_store(struct kvm_vcpu *vcpu, struct kvm_run *run);
 int kvm_handle_cp14_32(struct kvm_vcpu *vcpu, struct kvm_run *run);

arch/arm64/kvm/sys_regs.c

@@ -2109,17 +2109,10 @@ static int check_sysreg_table(const struct sys_reg_desc *table, unsigned int n,
 	return 0;
 }
 
-/* Target specific emulation tables */
-static struct kvm_sys_reg_target_table *target_tables[KVM_ARM_NUM_TARGETS];
-
-void kvm_register_target_sys_reg_table(unsigned int target,
-				       struct kvm_sys_reg_target_table *table)
+void kvm_check_target_sys_reg_table(struct kvm_sys_reg_target_table *table)
 {
-	if (check_sysreg_table(table->table64.table, table->table64.num, false) ||
-	    check_sysreg_table(table->table32.table, table->table32.num, true))
-		return;
-
-	target_tables[target] = table;
+	BUG_ON(check_sysreg_table(table->table64.table, table->table64.num, false));
+	BUG_ON(check_sysreg_table(table->table32.table, table->table32.num, true));
 }
 
 /* Get specific register table for this target. */
@@ -2127,9 +2120,8 @@ static const struct sys_reg_desc *get_target_table(unsigned target,
 						   bool mode_is_64,
 						   size_t *num)
 {
-	struct kvm_sys_reg_target_table *table;
+	struct kvm_sys_reg_target_table *table = &genericv8_target_table;
 
-	table = target_tables[target];
 	if (mode_is_64) {
 		*num = table->table64.num;
 		return table->table64.table;

arch/arm64/kvm/sys_regs.h

@@ -165,4 +165,6 @@ const struct sys_reg_desc *find_reg_by_id(u64 id,
 	CRn(sys_reg_CRn(reg)), CRm(sys_reg_CRm(reg)),	\
 	Op2(sys_reg_Op2(reg))
 
+extern struct kvm_sys_reg_target_table genericv8_target_table;
+
 #endif /* __ARM64_KVM_SYS_REGS_LOCAL_H__ */

arch/arm64/kvm/sys_regs_generic_v8.c

@@ -59,7 +59,7 @@ static const struct sys_reg_desc genericv8_cp15_regs[] = {
 	  access_actlr },
 };
 
-static struct kvm_sys_reg_target_table genericv8_target_table = {
+struct kvm_sys_reg_target_table genericv8_target_table = {
 	.table64 = {
 		.table = genericv8_sys_regs,
 		.num = ARRAY_SIZE(genericv8_sys_regs),
@@ -78,18 +78,7 @@ static int __init sys_reg_genericv8_init(void)
 		BUG_ON(cmp_sys_reg(&genericv8_sys_regs[i-1],
 			       &genericv8_sys_regs[i]) >= 0);
 
-	kvm_register_target_sys_reg_table(KVM_ARM_TARGET_AEM_V8,
-					  &genericv8_target_table);
-	kvm_register_target_sys_reg_table(KVM_ARM_TARGET_FOUNDATION_V8,
-					  &genericv8_target_table);
-	kvm_register_target_sys_reg_table(KVM_ARM_TARGET_CORTEX_A53,
-					  &genericv8_target_table);
-	kvm_register_target_sys_reg_table(KVM_ARM_TARGET_CORTEX_A57,
-					  &genericv8_target_table);
-	kvm_register_target_sys_reg_table(KVM_ARM_TARGET_XGENE_POTENZA,
-					  &genericv8_target_table);
-	kvm_register_target_sys_reg_table(KVM_ARM_TARGET_GENERIC_V8,
-					  &genericv8_target_table);
+	kvm_check_target_sys_reg_table(&genericv8_target_table);
 
 	return 0;
 }