arm64: kvm: use kvm_exception_table_entry

In subsequent patches we'll alter `struct exception_table_entry`, adding
fields that are not needed for KVM exception fixups.

In preparation for this, migrate KVM to its own `struct
kvm_exception_table_entry`, which is identical to the current format of
`struct exception_table_entry`. Comments are updated accordingly.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will@kernel.org>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211019160219.5202-5-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

arch/arm64/include/asm/kvm_asm.h

@@ -263,9 +263,10 @@ extern u64 __kvm_get_mdcr_el2(void);
 
 /*
  * KVM extable for unexpected exceptions.
- * In the same format _asm_extable, but output to a different section so that
- * it can be mapped to EL2. The KVM version is not sorted. The caller must
- * ensure:
+ * Create a struct kvm_exception_table_entry output to a section that can be
+ * mapped by EL2. The table is not sorted.
+ *
+ * The caller must ensure:
  * x18 has the hypervisor value to allow any Shadow-Call-Stack instrumented
  * code to write to it, and that SPSR_EL2 and ELR_EL2 are restored by the fixup.
  */

arch/arm64/kvm/hyp/include/hyp/switch.h

@@ -30,8 +30,12 @@
 #include <asm/processor.h>
 #include <asm/thread_info.h>
 
-extern struct exception_table_entry __start___kvm_ex_table;
-extern struct exception_table_entry __stop___kvm_ex_table;
+struct kvm_exception_table_entry {
+	int insn, fixup;
+};
+
+extern struct kvm_exception_table_entry __start___kvm_ex_table;
+extern struct kvm_exception_table_entry __stop___kvm_ex_table;
 
 /* Check whether the FP regs were dirtied while in the host-side run loop: */
 static inline bool update_fp_enabled(struct kvm_vcpu *vcpu)
@@ -510,7 +514,7 @@ static inline void __kvm_unexpected_el2_exception(void)
 {
 	extern char __guest_exit_panic[];
 	unsigned long addr, fixup;
-	struct exception_table_entry *entry, *end;
+	struct kvm_exception_table_entry *entry, *end;
 	unsigned long elr_el2 = read_sysreg(elr_el2);
 
 	entry = &__start___kvm_ex_table;