RISC-V: KVM: Break down the __kvm_riscv_switch_to() into macros

Break down the __kvm_riscv_switch_to() function into macros so that
these macros can be later re-used by SBI NACL extension based low-level
switch function.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20241020194734.58686-5-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>

Author: avpatel

arch/riscv/kvm/vcpu_switch.S

@@ -11,11 +11,7 @@
 #include <asm/asm-offsets.h>
 #include <asm/csr.h>
 
-	.text
-	.altmacro
-	.option norelax
-
-SYM_FUNC_START(__kvm_riscv_switch_to)
+.macro SAVE_HOST_GPRS
 	/* Save Host GPRs (except A0 and T0-T6) */
 	REG_S	ra, (KVM_ARCH_HOST_RA)(a0)
 	REG_S	sp, (KVM_ARCH_HOST_SP)(a0)
@@ -40,10 +36,12 @@ SYM_FUNC_START(__kvm_riscv_switch_to)
 	REG_S	s9, (KVM_ARCH_HOST_S9)(a0)
 	REG_S	s10, (KVM_ARCH_HOST_S10)(a0)
 	REG_S	s11, (KVM_ARCH_HOST_S11)(a0)
+.endm
 
+.macro SAVE_HOST_AND_RESTORE_GUEST_CSRS __resume_addr
 	/* Load Guest CSR values */
 	REG_L	t0, (KVM_ARCH_GUEST_SSTATUS)(a0)
-	la	t1, .Lkvm_switch_return
+	la	t1, \__resume_addr
 	REG_L	t2, (KVM_ARCH_GUEST_SEPC)(a0)
 
 	/* Save Host and Restore Guest SSTATUS */
@@ -62,7 +60,9 @@ SYM_FUNC_START(__kvm_riscv_switch_to)
 	REG_S	t0, (KVM_ARCH_HOST_SSTATUS)(a0)
 	REG_S	t1, (KVM_ARCH_HOST_STVEC)(a0)
 	REG_S	t3, (KVM_ARCH_HOST_SSCRATCH)(a0)
+.endm
 
+.macro RESTORE_GUEST_GPRS
 	/* Restore Guest GPRs (except A0) */
 	REG_L	ra, (KVM_ARCH_GUEST_RA)(a0)
 	REG_L	sp, (KVM_ARCH_GUEST_SP)(a0)
@@ -97,13 +97,9 @@ SYM_FUNC_START(__kvm_riscv_switch_to)
 
 	/* Restore Guest A0 */
 	REG_L	a0, (KVM_ARCH_GUEST_A0)(a0)
+.endm
 
-	/* Resume Guest */
-	sret
-
-	/* Back to Host */
-	.align 2
-.Lkvm_switch_return:
+.macro SAVE_GUEST_GPRS
 	/* Swap Guest A0 with SSCRATCH */
 	csrrw	a0, CSR_SSCRATCH, a0
 
@@ -138,7 +134,9 @@ SYM_FUNC_START(__kvm_riscv_switch_to)
 	REG_S	t4, (KVM_ARCH_GUEST_T4)(a0)
 	REG_S	t5, (KVM_ARCH_GUEST_T5)(a0)
 	REG_S	t6, (KVM_ARCH_GUEST_T6)(a0)
+.endm
 
+.macro SAVE_GUEST_AND_RESTORE_HOST_CSRS
 	/* Load Host CSR values */
 	REG_L	t0, (KVM_ARCH_HOST_STVEC)(a0)
 	REG_L	t1, (KVM_ARCH_HOST_SSCRATCH)(a0)
@@ -160,7 +158,9 @@ SYM_FUNC_START(__kvm_riscv_switch_to)
 	REG_S	t1, (KVM_ARCH_GUEST_A0)(a0)
 	REG_S	t2, (KVM_ARCH_GUEST_SSTATUS)(a0)
 	REG_S	t3, (KVM_ARCH_GUEST_SEPC)(a0)
+.endm
 
+.macro RESTORE_HOST_GPRS
 	/* Restore Host GPRs (except A0 and T0-T6) */
 	REG_L	ra, (KVM_ARCH_HOST_RA)(a0)
 	REG_L	sp, (KVM_ARCH_HOST_SP)(a0)
@@ -185,6 +185,34 @@ SYM_FUNC_START(__kvm_riscv_switch_to)
 	REG_L	s9, (KVM_ARCH_HOST_S9)(a0)
 	REG_L	s10, (KVM_ARCH_HOST_S10)(a0)
 	REG_L	s11, (KVM_ARCH_HOST_S11)(a0)
+.endm
+
+	.text
+	.altmacro
+	.option norelax
+
+	/*
+	 * Parameters:
+	 * A0 <= Pointer to struct kvm_vcpu_arch
+	 */
+SYM_FUNC_START(__kvm_riscv_switch_to)
+	SAVE_HOST_GPRS
+
+	SAVE_HOST_AND_RESTORE_GUEST_CSRS .Lkvm_switch_return
+
+	RESTORE_GUEST_GPRS
+
+	/* Resume Guest using SRET */
+	sret
+
+	/* Back to Host */
+	.align 2
+.Lkvm_switch_return:
+	SAVE_GUEST_GPRS
+
+	SAVE_GUEST_AND_RESTORE_HOST_CSRS
+
+	RESTORE_HOST_GPRS
 
 	/* Return to C code */
 	ret