MIPS: KVM/locore.S: Only preserve callee saved registers

Update __kvm_mips_vcpu_run() to only save and restore callee saved
registers. It is always called using the standard ABIs, so the caller
will preserve any other registers that need preserving.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13208/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kvm/locore.S

@@ -53,40 +53,14 @@
 FEXPORT(__kvm_mips_vcpu_run)
 	/* k0/k1 not being used in host kernel context */
 	INT_ADDIU k1, sp, -PT_SIZE
-	LONG_S	$0, PT_R0(k1)
-	LONG_S	$1, PT_R1(k1)
-	LONG_S	$2, PT_R2(k1)
-	LONG_S	$3, PT_R3(k1)
-
-	LONG_S	$4, PT_R4(k1)
-	LONG_S	$5, PT_R5(k1)
-	LONG_S	$6, PT_R6(k1)
-	LONG_S	$7, PT_R7(k1)
-
-	LONG_S	$8,  PT_R8(k1)
-	LONG_S	$9,  PT_R9(k1)
-	LONG_S	$10, PT_R10(k1)
-	LONG_S	$11, PT_R11(k1)
-	LONG_S	$12, PT_R12(k1)
-	LONG_S	$13, PT_R13(k1)
-	LONG_S	$14, PT_R14(k1)
-	LONG_S	$15, PT_R15(k1)
 	LONG_S	$16, PT_R16(k1)
 	LONG_S	$17, PT_R17(k1)
-
 	LONG_S	$18, PT_R18(k1)
 	LONG_S	$19, PT_R19(k1)
 	LONG_S	$20, PT_R20(k1)
 	LONG_S	$21, PT_R21(k1)
 	LONG_S	$22, PT_R22(k1)
 	LONG_S	$23, PT_R23(k1)
-	LONG_S	$24, PT_R24(k1)
-	LONG_S	$25, PT_R25(k1)
-
-	/*
-	 * XXXKYMA k0/k1 not saved, not being used if we got here through
-	 * an ioctl()
-	 */
 
 	LONG_S	$28, PT_R28(k1)
 	LONG_S	$29, PT_R29(k1)
@@ -545,10 +519,6 @@ __kvm_mips_return_to_host:
 	LONG_L	k0, PT_HOST_USERLOCAL(k1)
 	mtc0	k0, CP0_DDATA_LO
 
-	/* Load context saved on the host stack */
-	LONG_L	$0, PT_R0(k1)
-	LONG_L	$1, PT_R1(k1)
-
 	/*
 	 * r2/v0 is the return code, shift it down by 2 (arithmetic)
 	 * to recover the err code
@@ -556,19 +526,7 @@ __kvm_mips_return_to_host:
 	INT_SRA	k0, v0, 2
 	move	$2, k0
 
-	LONG_L	$3, PT_R3(k1)
-	LONG_L	$4, PT_R4(k1)
-	LONG_L	$5, PT_R5(k1)
-	LONG_L	$6, PT_R6(k1)
-	LONG_L	$7, PT_R7(k1)
-	LONG_L	$8, PT_R8(k1)
-	LONG_L	$9, PT_R9(k1)
-	LONG_L	$10, PT_R10(k1)
-	LONG_L	$11, PT_R11(k1)
-	LONG_L	$12, PT_R12(k1)
-	LONG_L	$13, PT_R13(k1)
-	LONG_L	$14, PT_R14(k1)
-	LONG_L	$15, PT_R15(k1)
+	/* Load context saved on the host stack */
 	LONG_L	$16, PT_R16(k1)
 	LONG_L	$17, PT_R17(k1)
 	LONG_L	$18, PT_R18(k1)
@@ -577,10 +535,6 @@ __kvm_mips_return_to_host:
 	LONG_L	$21, PT_R21(k1)
 	LONG_L	$22, PT_R22(k1)
 	LONG_L	$23, PT_R23(k1)
-	LONG_L	$24, PT_R24(k1)
-	LONG_L	$25, PT_R25(k1)
-
-	/* Host k0/k1 were not saved */
 
 	LONG_L	$28, PT_R28(k1)
 	LONG_L	$29, PT_R29(k1)