arm/Kconfig: Always select SEMIHOSTING when TCG is present

We are about to enable the build without TCG, so CONFIG_SEMIHOSTING
and CONFIG_ARM_COMPATIBLE_SEMIHOSTING cannot be unconditionally set in
default.mak anymore. So reflect the change in a Kconfig.

Instead of using semihosting/Kconfig, use a target-specific file, so
that the change doesn't affect other architectures which might
implement semihosting in a way compatible with KVM.

The selection from ARM_v7M needs to be removed to avoid a cycle during
parsing.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230426180013.14814-11-farosas@suse.de
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

configs/devices/arm-softmmu/default.mak

@@ -40,6 +40,4 @@ CONFIG_MICROBIT=y
 CONFIG_FSL_IMX25=y
 CONFIG_FSL_IMX7=y
 CONFIG_FSL_IMX6UL=y
-CONFIG_SEMIHOSTING=y
-CONFIG_ARM_COMPATIBLE_SEMIHOSTING=y
 CONFIG_ALLWINNER_H3=y

hw/arm/Kconfig

@@ -317,7 +317,6 @@ config ARM_V7M
     # currently v7M must be included in a TCG build due to translate.c
     default y if TCG && (ARM || AARCH64)
     select PTIMER
-    select ARM_COMPATIBLE_SEMIHOSTING
 
 config ALLWINNER_A10
     bool

target/arm/Kconfig

@@ -4,3 +4,10 @@ config ARM
 config AARCH64
     bool
     select ARM
+
+# This config exists just so we can make SEMIHOSTING default when TCG
+# is selected without also changing it for other architectures.
+config ARM_SEMIHOSTING
+    bool
+    default y if TCG && ARM
+    select ARM_COMPATIBLE_SEMIHOSTING