prephv: cleanup, README

I haven't written enough worth sharing, but I've written
enough that would be terrible to lose...so time to share it
away.

Signed-off-by: Andrei Warkentin <andrey.warkentin@gmail.com>

Makefile

@@ -1,20 +1,19 @@
 ENV_FILE=build_env
 -include $(ENV_FILE)
 
+SHELL := /bin/bash
+
 OBJ = entry.o main.o console.o lib/string.o fdt.o fdt_strerror.o fdt_ro.o exc-vecs.o guest.o \
       exc.o time.o mmu.o mem.o opal.o cache.o rom.o lib/ctype.o lib/vsprintf.o log.o lib/malloc.o \
       fat/fat_cache.o    fat/fat_format.o  fat/fat_string.o  fat/fat_write.o \
       fat/fat_access.o  fat/fat_filelib.o  fat/fat_misc.o    fat/fat_table.o
 
 NAME = prephv
 
-ifeq ($(CONFIG_MAMBO), 1)
-BUILD_FLAGS = -DCONFIG_MAMBO
-OBJ += mambo.o
-endif
-
 CROSS ?= ppc64le-linux
 CC = $(CROSS)-gcc
+PPC64QEMU ?= qemu-system-ppc64
+FAT_IMAGE ?= ../image.fat # relative to skiboot
 
 ARCH_FLAGS = -msoft-float -mpowerpc64 -mcpu=power8 -mtune=power8 -mabi=elfv2 \
              -mlittle-endian -mno-strict-align -mno-multiple \
@@ -42,6 +41,8 @@ clean_env: log_clean_env clean
 	@echo OLD_BUILD_ENV=\"$(BUILD_ENV)\" > $(ENV_FILE)
 
 test: $(NAME) skiboot/skiboot.lid
+	$(shell pushd skiboot && $(PPC64QEMU) -m 4G -M powernv -nographic -kernel ../prephv  -initrd $(FAT_IMAGE) 1>&2 || 0)
+	$(shell reset)
 
 skiboot/skiboot.lid:
 	git submodule update --init skiboot

README.md

@@ -0,0 +1,92 @@
+prephv - because I wasted my 90's playing with LEGOs.
+=====================================================
+
+This is mostly a huge ugly hack, derived from my
+ppc64le_hello code. The running philosophy here is
+to throw things together late at night with my family
+asleep and see how far I get without a real design
+or without a real desire to implement boring things
+like IDE (*sigh*) emulation. PowerPC things though
+are considered fun and crucial...anyway...
+
+It's a 64-bit LE ``hypervisor'', running a single 32-bit
+LE VM, with the intention of modelling some as of yet
+unknown PReP machine...eventually hopefully enough to BSOD
+inside the Windows NT 4.0 PowerPC kernel.
+
+PReP is a long dead specification for consumer-ish PowerPC
+servers and workstations, that basically amounted to a
+pre-ACPI PC with a PowerPC CPU. Some PReP machines ran
+Windows NT 4.0. Most ran AIX, an obscure Solaris port, or
+gave Linux hackers many fun restless nights.
+
+Relieve '96... I spent that July basking on the beaches of
+Cagliari. Somewhere in a dusty office in Seattle people
+were dealing with stuff like this:
+
+    Open Firmware ARC Interface  Version 3.0 (Jul 12 1996 - 18:46:44)
+    Couldn't claim SYSTEM PARAMETER BLOCK
+    Program complete - please reboot.
+
+Status
+------
+
+Today I fake out enough of OpenFirware client interface to
+successfully run the VENEER.EXE ARC shim and hand off to
+SETUPLDR. Not much else. Specifically, the CPU VM state is
+not modelled quite well (or at all...?).
+
+![ARC veneer image](/docs/veneer.png?raw=true "In ARC menu")
+![setupldr image](/docs/setupldr.png?raw=true "In SETUPLDR")
+
+The "disk" is passed as initrd. This is nowhere near
+being able to run any portion of NT kernel.
+
+Building
+--------
+
+You will need a LE 64-bit toolchain to build (i.e. ppc64le-linux).
+A good source of toolchains is kernel.org. For building skiboot
+(for testing) you will also need the BE 64-bit toolchain
+(i.e. powerpc64-linux).
+
+Skiboot is pulled-in as a submodule. Prephv is a skiboot payload.
+So hypothetically it could run on a real Power8 box.
+
+You will need Benjamin Herrenschmidt's PowerNV QEMU tree.
+
+Good directions for QEMU/PowerNV:
+https://www.flamingspork.com/blog/2015/08/28/running-opal-in-qemu-the-powernv-platform/
+
+    $ make
+
+Running
+-------
+
+You now need an image.fat that contains at least the following
+files from the NT 4.0 CD, which are obviously not distributable:
+- \veneer.exe    from /PPC/VENEER.EXE
+- \osloader.exe  from /PPC/SETUPLDR
+
+I've used FAT16. Other FAT types are untested. Good luck.
+
+    $ PPC64QEMU=/path/to/BenH/powernv/qemu make test
+
+TODO
+----
+
+- Everything
+- Threads (+implement an interactive monitor/debugger)
+
+Resources
+---------
+
+Useful stuff:
+- PowerISA_V2.07_PUBLIC.pdf             - Book 3S
+- ABI53BitOpenPOWER_21July2014_pub.pdf  - ELFv2 ABI used for PPC64LE
+- P8_um_external_v1.1_2015JAN29_pub.pdf - POWER8 User Manual
+
+Contact Info
+------------
+
+Andrei Warkentin (andrey.warkentin@gmail.com).

entry.S

@@ -112,9 +112,4 @@ _GLOBAL(_start)
 	 * like, so we keep it.
 	 */
 	ori	r0, r0, 0
-#ifdef CONFIG_MAMBO
-	/*
-	 * Stop sim.
-	 */
-	attn
-#endif /* CONFIG_MAMBO */
+	never:	b	.

exc.c

@@ -62,8 +62,7 @@ exc_handler(eframe_t *frame)
 
 	/*
 	 * Handle instruction storage faults within the HV address
-	 * region (which is direct-mapped to 0). When the MMU is off,
-	 * the translation happens automatically.
+	 * region (which is direct-mapped to 0).
 	 */
 	if (frame->vec == EXC_ISI) {
 		if (frame->hsrr0 >= HV_ASPACE &&
@@ -78,8 +77,7 @@ exc_handler(eframe_t *frame)
 
 	/*
 	 * Handle data storage faults within the HV address
-	 * region (which is direct-mapped to 0). When the MMU is off,
-	 * the translation happens automatically.
+	 * region (which is direct-mapped to 0).
 	 */
 	if (frame->vec == EXC_DSI) {
 		if (get_DAR() >= HV_ASPACE &&
@@ -97,13 +95,6 @@ exc_handler(eframe_t *frame)
 		exc_rfi(frame);
 	}
 
-	if (frame->vec == EXC_HDEC) {
-		set_HDEC(DEC_DISABLE);
-		LOG("hypervisor decrementer, exception handler with MMU %s!",
-		       (frame->hsrr1 & (MSR_IR | MSR_DR)) ? "on" : "off");
-		exc_rfi(frame);
-	}
-
 	if (frame->vec == EXC_SC) {
 		mtmsrd(MSR_RI, 1);
 		if (rom_call(frame) == ERR_NONE) {
@@ -174,20 +165,6 @@ exc_enable_ee(void)
 }
 
 
-void
-exc_enable_hdec(void)
-{
-	set_LPCR(get_LPCR() | LPCR_HDICE);
-}
-
-
-void
-exc_disable_hdec(void)
-{
-	set_LPCR(get_LPCR() & ~LPCR_HDICE);
-}
-
-
 void
 exc_init(void)
 {