QEMU TCG on 64 bit systems should not require 1GB for code generator buffer....

QEMU TCG on 64 bit systems should not require 1GB for code generator buffer. Old default of 32MB is sufficient

Makefile

@@ -7,6 +7,7 @@ i386:
 	mount --bind tmp /var/tmp
 
 	tar xf qemu-5.0.0.tar.xz
+	patch -Np1 -d qemu-5.0.0 < qemu-5.0.0-reduce_default_code_gen_buffer.patch
 	cd qemu-5.0.0 && ./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var --target-list=i386-softmmu,i386-linux-user
 	$(MAKE) -C qemu-5.0.0
 	$(MAKE) -C qemu-5.0.0 check
@@ -27,6 +28,7 @@ x86_64:
 	mount --bind tmp /var/tmp
 
 	tar xf qemu-5.0.0.tar.xz
+	patch -Np1 -d qemu-5.0.0 < qemu-5.0.0-reduce_default_code_gen_buffer.patch
 	cd qemu-5.0.0 && ./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var --target-list=x86_64-softmmu,x86_64-linux-user
 	$(MAKE) -C qemu-5.0.0
 	$(MAKE) -C qemu-5.0.0 check
@@ -51,6 +53,7 @@ arm:
 	mount --bind tmp /var/tmp
 
 	tar xf qemu-5.0.0.tar.xz
+	patch -Np1 -d qemu-5.0.0 < qemu-5.0.0-reduce_default_code_gen_buffer.patch
 	cd qemu-5.0.0 && ./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var --target-list=arm-softmmu,arm-linux-user,armeb-linux-user
 	$(MAKE) -C qemu-5.0.0
 	$(MAKE) -C qemu-5.0.0 check
@@ -75,6 +78,7 @@ aarch64:
 	mount --bind tmp /var/tmp
 
 	tar xf qemu-5.0.0.tar.xz
+	patch -Np1 -d qemu-5.0.0 < qemu-5.0.0-reduce_default_code_gen_buffer.patch
 	cd qemu-5.0.0 && ./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var --target-list=aarch64-softmmu,aarch64-linux-user,aarch64_be-linux-user
 	$(MAKE) -C qemu-5.0.0
 	$(MAKE) -C qemu-5.0.0 check

qemu-5.0.0-reduce_default_code_gen_buffer.patch

+diff -uNr qemu-5.0.0/accel/tcg/translate-all.c qemu-5.0.0-reduce_default_code_gen_buffer/accel/tcg/translate-all.c
+--- qemu-5.0.0/accel/tcg/translate-all.c	2020-04-29 02:19:24.000000000 +0930
++++ qemu-5.0.0-reduce_default_code_gen_buffer/accel/tcg/translate-all.c	2021-09-19 23:35:04.670316863 +0930
+@@ -944,7 +944,7 @@
+  * Users running large scale system emulation may want to tweak their
+  * runtime setup via the tb-size control on the command line.
+  */
+-#define DEFAULT_CODE_GEN_BUFFER_SIZE_1 (1 * GiB)
++#define DEFAULT_CODE_GEN_BUFFER_SIZE_1 (32 * MiB)
+ #endif
+ #endif
+