[PATCH v5 0/2] Minimal build for RISCV

[PATCH v5 0/2] Minimal build for RISCV

[Connor Davis]

Hi all,

This series introduces a minimal build for RISCV. It is based on Bobby's
previous work from last year[0] rebased onto current Xen.

This series provides the patches necessary to get a minimal build
working. The build is "minimal" in the sense that it only supports
building TARGET=riscv64/head.o. The arch/riscv/riscv64/head.S is just
a simple while(1).

The first patch is a mod to non-RISCV bits that enable building a
config with !CONFIG_HAS_NS16550.

The second patch adds the make/Kconfig boilerplate alongside head.S and
asm-riscv/config.h (head.S references ENTRY that is defined in
asm-riscv/config.h).

[0] https://lore.kernel.org/xen-devel/cover.1579615303.git.bobbyeshleman@gmail.com/

Thanks,
Connor

--
Changes since v4:
  - Dropped patches 2 and 4 as these have been applied
  - Moved arch/riscv/head.S to arch/riscv/riscv64/head.S for consistency
    with ARM.
  - Added Bob and myself to MAINTAINERS

Changes since v3:
  - Dropped "xen: Fix build when !CONFIG_GRANT_TABLE" since this was
    applied by Jan
  - Adjusted Kconfig condition for building NS16550
  - Use bool rather than bool_t
  - Removed riscv memory map, as this should probably be done later once
    the frametable size is figured out
  - Consolidated 64-bit #defines in asm-riscv/config.h
  - Renamed riscv64_defconfig to tiny64_defconfig, added CONFIG_DEBUG
    and CONFIG_DEBUG_INFO
  - Fixed logic/alignment/whitespace issues in Kconfig files
  - Use upstream archlinux riscv64 cross-compiler packages instead of
    custom built toolchain in docker container

Changes since v2:
  - Reduced number of riscv files added to ease review

Changes since v1:
  - Dropped "xen/sched: Fix build when NR_CPUS == 1" since this was
    fixed for 4.15
  - Moved #ifdef-ary around iommu_enabled to iommu.h
  - Moved struct grant_table declaration above ifdef CONFIG_GRANT_TABLE
    instead of defining an empty struct when !CONFIG_GRANT_TABLE

--
Connor Davis (2):
  xen/char: Default HAS_NS16550 to y only for X86 and ARM
  xen: Add files needed for minimal riscv build

 MAINTAINERS                             |  8 +++++
 config/riscv64.mk                       |  5 +++
 xen/Makefile                            |  8 +++--
 xen/arch/riscv/Kconfig                  | 47 +++++++++++++++++++++++++
 xen/arch/riscv/Kconfig.debug            |  0
 xen/arch/riscv/Makefile                 |  2 ++
 xen/arch/riscv/Rules.mk                 |  0
 xen/arch/riscv/arch.mk                  | 14 ++++++++
 xen/arch/riscv/configs/tiny64_defconfig | 13 +++++++
 xen/arch/riscv/riscv64/asm-offsets.c    |  0
 xen/arch/riscv/riscv64/head.S           |  6 ++++
 xen/drivers/char/Kconfig                |  1 +
 xen/include/asm-riscv/config.h          | 47 +++++++++++++++++++++++++
 13 files changed, 149 insertions(+), 2 deletions(-)
 create mode 100644 config/riscv64.mk
 create mode 100644 xen/arch/riscv/Kconfig
 create mode 100644 xen/arch/riscv/Kconfig.debug
 create mode 100644 xen/arch/riscv/Makefile
 create mode 100644 xen/arch/riscv/Rules.mk
 create mode 100644 xen/arch/riscv/arch.mk
 create mode 100644 xen/arch/riscv/configs/tiny64_defconfig
 create mode 100644 xen/arch/riscv/riscv64/asm-offsets.c
 create mode 100644 xen/arch/riscv/riscv64/head.S
 create mode 100644 xen/include/asm-riscv/config.h

-- 
2.31.1

[PATCH v5 1/2] xen/char: Default HAS_NS16550 to y only for X86 and ARM

[Connor Davis]

Defaulting to yes only for X86 and ARM reduces the requirements
for a minimal build when porting new architectures.

Signed-off-by: Connor Davis <connojdavis@gmail.com>
---
 xen/drivers/char/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/xen/drivers/char/Kconfig b/xen/drivers/char/Kconfig
index b572305657..2ff5b288e2 100644
--- a/xen/drivers/char/Kconfig
+++ b/xen/drivers/char/Kconfig
@@ -1,5 +1,6 @@
 config HAS_NS16550
 	bool "NS16550 UART driver" if ARM
+	default n if RISCV
 	default y
 	help
 	  This selects the 16550-series UART support. For most systems, say Y.
-- 
2.31.1

[PATCH v5 2/2] xen: Add files needed for minimal riscv build

[Connor Davis]

Add arch-specific makefiles and configs needed to build for
riscv. Also add a minimal head.S that is a simple infinite loop.
head.o can be built with

$ make XEN_TARGET_ARCH=riscv64 SUBSYSTEMS=xen -C xen tiny64_defconfig
$ make XEN_TARGET_ARCH=riscv64 SUBSYSTEMS=xen -C xen TARGET=riscv64/head.o

No other TARGET is supported at the moment.

Signed-off-by: Connor Davis <connojdavis@gmail.com>
---
Bob: I moved back to XEN_TARGET_ARCH=riscv64 because supplying
just XEN_TARGET_ARCH=riscv causes TARGET_ARCH == TARGET_SUBARCH, and
that broke the build after the recent commit b6ecd5c8bc
"build: centralize / unify asm-offsets generation". It also deviates
from how x86 and arm work now, so I think this change is for the best
for now. That commit is also why the PHONY include target is added
in the riscv/Makefile.
---
 MAINTAINERS                             |  8 +++++
 config/riscv64.mk                       |  5 +++
 xen/Makefile                            |  8 +++--
 xen/arch/riscv/Kconfig                  | 47 +++++++++++++++++++++++++
 xen/arch/riscv/Kconfig.debug            |  0
 xen/arch/riscv/Makefile                 |  2 ++
 xen/arch/riscv/Rules.mk                 |  0
 xen/arch/riscv/arch.mk                  | 14 ++++++++
 xen/arch/riscv/configs/tiny64_defconfig | 13 +++++++
 xen/arch/riscv/riscv64/asm-offsets.c    |  0
 xen/arch/riscv/riscv64/head.S           |  6 ++++
 xen/include/asm-riscv/config.h          | 47 +++++++++++++++++++++++++
 12 files changed, 148 insertions(+), 2 deletions(-)
 create mode 100644 config/riscv64.mk
 create mode 100644 xen/arch/riscv/Kconfig
 create mode 100644 xen/arch/riscv/Kconfig.debug
 create mode 100644 xen/arch/riscv/Makefile
 create mode 100644 xen/arch/riscv/Rules.mk
 create mode 100644 xen/arch/riscv/arch.mk
 create mode 100644 xen/arch/riscv/configs/tiny64_defconfig
 create mode 100644 xen/arch/riscv/riscv64/asm-offsets.c
 create mode 100644 xen/arch/riscv/riscv64/head.S
 create mode 100644 xen/include/asm-riscv/config.h

diff --git a/MAINTAINERS b/MAINTAINERS
index d46b08a0d2..956e71220d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -456,6 +456,14 @@ F:	tools/libs/light/libxl_nonetbuffer.c
 F:	tools/hotplug/Linux/remus-netbuf-setup
 F:	tools/hotplug/Linux/block-drbd-probe
 
+RISCV
+M:	Bob Eshleman <bobbyeshleman@gmail.com>
+R:	Connor Davis <connojdavis@gmail.com>
+S:	Supported
+F:	config/riscv64.mk
+F:	xen/arch/riscv/
+F:	xen/include/asm-riscv/
+
 RTDS SCHEDULER
 M:	Dario Faggioli <dfaggioli@suse.com>
 M:	Meng Xu <mengxu@cis.upenn.edu>
diff --git a/config/riscv64.mk b/config/riscv64.mk
new file mode 100644
index 0000000000..a5a21e5fa2
--- /dev/null
+++ b/config/riscv64.mk
@@ -0,0 +1,5 @@
+CONFIG_RISCV := y
+CONFIG_RISCV_64 := y
+CONFIG_RISCV_$(XEN_OS) := y
+
+CONFIG_XEN_INSTALL_SUFFIX :=
diff --git a/xen/Makefile b/xen/Makefile
index 7ce7692354..89879fad4c 100644
--- a/xen/Makefile
+++ b/xen/Makefile
@@ -26,7 +26,9 @@ MAKEFLAGS += -rR
 EFI_MOUNTPOINT ?= $(BOOT_DIR)/efi
 
 ARCH=$(XEN_TARGET_ARCH)
-SRCARCH=$(shell echo $(ARCH) | sed -e 's/x86.*/x86/' -e s'/arm\(32\|64\)/arm/g')
+SRCARCH=$(shell echo $(ARCH) | \
+          sed -e 's/x86.*/x86/' -e s'/arm\(32\|64\)/arm/g' \
+              -e s'/riscv.*/riscv/g')
 
 # Don't break if the build process wasn't called from the top level
 # we need XEN_TARGET_ARCH to generate the proper config
@@ -35,7 +37,8 @@ include $(XEN_ROOT)/Config.mk
 # Set ARCH/SUBARCH appropriately.
 export TARGET_SUBARCH  := $(XEN_TARGET_ARCH)
 export TARGET_ARCH     := $(shell echo $(XEN_TARGET_ARCH) | \
-                            sed -e 's/x86.*/x86/' -e s'/arm\(32\|64\)/arm/g')
+                            sed -e 's/x86.*/x86/' -e s'/arm\(32\|64\)/arm/g' \
+                                -e s'/riscv.*/riscv/g')
 
 # Allow someone to change their config file
 export KCONFIG_CONFIG ?= .config
@@ -335,6 +338,7 @@ _clean: delete-unfresh-files
 	$(MAKE) $(clean) xsm
 	$(MAKE) $(clean) crypto
 	$(MAKE) $(clean) arch/arm
+	$(MAKE) $(clean) arch/riscv
 	$(MAKE) $(clean) arch/x86
 	$(MAKE) $(clean) test
 	$(MAKE) -f $(BASEDIR)/tools/kconfig/Makefile.kconfig ARCH=$(ARCH) SRCARCH=$(SRCARCH) clean
diff --git a/xen/arch/riscv/Kconfig b/xen/arch/riscv/Kconfig
new file mode 100644
index 0000000000..bd8381c5e0
--- /dev/null
+++ b/xen/arch/riscv/Kconfig
@@ -0,0 +1,47 @@
+config RISCV
+	def_bool y
+
+config RISCV_64
+	def_bool y
+	select 64BIT
+
+config ARCH_DEFCONFIG
+	string
+	default "arch/riscv/configs/tiny64_defconfig"
+
+menu "Architecture Features"
+
+source "arch/Kconfig"
+
+endmenu
+
+menu "ISA Selection"
+
+choice
+	prompt "Base ISA"
+	default RISCV_ISA_RV64IMA if RISCV_64
+	help
+	  This selects the base ISA extensions that Xen will target.
+
+config RISCV_ISA_RV64IMA
+	bool "RV64IMA"
+	help
+	  Use the RV64I base ISA, plus the "M" and "A" extensions
+	  for integer multiply/divide and atomic instructions, respectively.
+
+endchoice
+
+config RISCV_ISA_C
+	bool "Compressed extension"
+	help
+	  Add "C" to the ISA subsets that the toolchain is allowed to
+	  emit when building Xen, which results in compressed instructions
+	  in the Xen binary.
+
+	  If unsure, say N.
+
+endmenu
+
+source "common/Kconfig"
+
+source "drivers/Kconfig"
diff --git a/xen/arch/riscv/Kconfig.debug b/xen/arch/riscv/Kconfig.debug
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/xen/arch/riscv/Makefile b/xen/arch/riscv/Makefile
new file mode 100644
index 0000000000..942e4ffbc1
--- /dev/null
+++ b/xen/arch/riscv/Makefile
@@ -0,0 +1,2 @@
+.PHONY: include
+include:
diff --git a/xen/arch/riscv/Rules.mk b/xen/arch/riscv/Rules.mk
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/xen/arch/riscv/arch.mk b/xen/arch/riscv/arch.mk
new file mode 100644
index 0000000000..53dadb8975
--- /dev/null
+++ b/xen/arch/riscv/arch.mk
@@ -0,0 +1,14 @@
+########################################
+# RISCV-specific definitions
+
+CFLAGS-$(CONFIG_RISCV_64) += -mabi=lp64
+
+riscv-march-$(CONFIG_RISCV_ISA_RV64IMA) := rv64ima
+riscv-march-$(CONFIG_RISCV_ISA_C)       := $(riscv-march-y)c
+
+# Note that -mcmodel=medany is used so that Xen can be mapped
+# into the upper half _or_ the lower half of the address space.
+# -mcmodel=medlow would force Xen into the lower half.
+
+CFLAGS += -march=$(riscv-march-y) -mstrict-align -mcmodel=medany
+CFLAGS += -I$(BASEDIR)/include
diff --git a/xen/arch/riscv/configs/tiny64_defconfig b/xen/arch/riscv/configs/tiny64_defconfig
new file mode 100644
index 0000000000..3c9a2ff941
--- /dev/null
+++ b/xen/arch/riscv/configs/tiny64_defconfig
@@ -0,0 +1,13 @@
+# CONFIG_SCHED_CREDIT is not set
+# CONFIG_SCHED_RTDS is not set
+# CONFIG_SCHED_NULL is not set
+# CONFIG_SCHED_ARINC653 is not set
+# CONFIG_TRACEBUFFER is not set
+# CONFIG_HYPFS is not set
+# CONFIG_GRANT_TABLE is not set
+# CONFIG_SPECULATIVE_HARDEN_ARRAY is not set
+
+CONFIG_RISCV_64=y
+CONFIG_DEBUG=y
+CONFIG_DEBUG_INFO=y
+CONFIG_EXPERT=y
diff --git a/xen/arch/riscv/riscv64/asm-offsets.c b/xen/arch/riscv/riscv64/asm-offsets.c
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/xen/arch/riscv/riscv64/head.S b/xen/arch/riscv/riscv64/head.S
new file mode 100644
index 0000000000..0dbc27ba75
--- /dev/null
+++ b/xen/arch/riscv/riscv64/head.S
@@ -0,0 +1,6 @@
+#include <asm/config.h>
+
+        .text
+
+ENTRY(start)
+        j  start
diff --git a/xen/include/asm-riscv/config.h b/xen/include/asm-riscv/config.h
new file mode 100644
index 0000000000..e2ae21de61
--- /dev/null
+++ b/xen/include/asm-riscv/config.h
@@ -0,0 +1,47 @@
+#ifndef __RISCV_CONFIG_H__
+#define __RISCV_CONFIG_H__
+
+#if defined(CONFIG_RISCV_64)
+# define LONG_BYTEORDER 3
+# define ELFSIZE 64
+# define MAX_VIRT_CPUS 128u
+#else
+# error "Unsupported RISCV variant"
+#endif
+
+#define BYTES_PER_LONG (1 << LONG_BYTEORDER)
+#define BITS_PER_LONG  (BYTES_PER_LONG << 3)
+#define POINTER_ALIGN  BYTES_PER_LONG
+
+#define BITS_PER_LLONG 64
+
+/* xen_ulong_t is always 64 bits */
+#define BITS_PER_XEN_ULONG 64
+
+#define CONFIG_RISCV_L1_CACHE_SHIFT 6
+#define CONFIG_PAGEALLOC_MAX_ORDER  18
+#define CONFIG_DOMU_MAX_ORDER       9
+#define CONFIG_HWDOM_MAX_ORDER      10
+
+#define OPT_CONSOLE_STR "dtuart"
+#define INVALID_VCPU_ID MAX_VIRT_CPUS
+
+/* Linkage for RISCV */
+#ifdef __ASSEMBLY__
+#define ALIGN .align 2
+
+#define ENTRY(name)                                \
+  .globl name;                                     \
+  ALIGN;                                           \
+  name:
+#endif
+
+#endif /* __RISCV_CONFIG_H__ */
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
-- 
2.31.1

Re: [PATCH v5 1/2] xen/char: Default HAS_NS16550 to y only for X86 and ARM

[Jan Beulich]

On 02.06.2021 17:08, Connor Davis wrote:
> Defaulting to yes only for X86 and ARM reduces the requirements
> for a minimal build when porting new architectures.
> 
> Signed-off-by: Connor Davis <connojdavis@gmail.com>

Please can you accumulate tags you've already got into re-submissions,
so the status of patches is clear and committers will know what is
ready to go in without having to hunt down anything? In the case here
you've lost my A-b.

Jan

Re: [PATCH v5 1/2] xen/char: Default HAS_NS16550 to y only for X86 and ARM

[Connor Davis]

On 6/2/21 9:52 AM, Jan Beulich wrote:
> On 02.06.2021 17:08, Connor Davis wrote:
>> Defaulting to yes only for X86 and ARM reduces the requirements
>> for a minimal build when porting new architectures.
>>
>> Signed-off-by: Connor Davis <connojdavis@gmail.com>
> Please can you accumulate tags you've already got into re-submissions,
> so the status of patches is clear and committers will know what is
> ready to go in without having to hunt down anything? In the case here
> you've lost my A-b.
>
> Jan
Oops, sorry about that. Will resend shortly.

Thanks,
Connor