Date: Sun, 1 Mar 2015 00:49:41 -0800 From: Mark Millard <markmi@dsl-only.net> To: FreeBSD PowerPC ML <freebsd-ppc@freebsd.org>, Nathan Whitehorn <nwhitehorn@freebsd.org>, Justin Hibbits <chmeeedalf@gmail.com> Subject: Re: Large RAM Powermac G5 powerpc64 openfirmware entry point use: I seem to have removed the major/frequent boot problem(s) Message-ID: <B55BECD6-5B1E-49F1-A152-9BFC85974BE1@dsl-only.net> In-Reply-To: <EF1EC459-BC46-42D5-9C3D-ABCBEF90AC44@dsl-only.net> References: <EF1EC459-BC46-42D5-9C3D-ABCBEF90AC44@dsl-only.net>
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Having a working code combination and switching to finding the minimal =
change to FreeBSD's powerpc64 code that preserves the good behavior has =
shown that the required change to FreeBSD's powerpc64 code is tiny.
The code that must be changed for PowerMac G5 contexts is in =
ofw_sprg_prepare:
__asm __volatile("mfsprg0 %0\n\t"
"mtsprg0 %1\n\t"
"mtsprg1 %2\n\t"
"mtsprg2 %3\n\t"
"mtsprg3 %4\n\t"
: "=3D&r"(ofw_sprg0_save)
: "r"(ofmsr[1]),
"r"(ofmsr[2]),
"r"(ofmsr[3]),
"r"(ofmsr[4]));
Specifically, the "mtsprg0 %1\n\t" must not be done: the FreeBSD SPRG0 =
value must be left in place before the use of ofwcall. The PowerMac G5 =
openfirmware treats SPRG0 as a scratch register initially (and later), =
not as having a value that must be preserved. SPRG0 from before FreeBSD =
has no stable initial value to put back here.
PowerMac G5 openfirmware entry point code does save SPRG0-SPRG3 but =
later depends on SPRG3's unchanged value to point to a pointer to use to =
store information. So "mtsprg3 %4\n\t" is required to be in place before =
the use of ofwcall: openfirmware requires the value, much like FreeBSD =
requires SPRG0 to be in place.
"mtsprg1 %2\n\t" and "mtsprg2 %3\n\t" are not needed but do not harm =
anything: Both FreeBSD and PowerMac G5 openfirmware treat them as =
scratch.
I've tested such changes with both 10.1-STABLE's ofwcall64.S and =
11.0-CURRENT's ofwcall64.S (substituted into 10.1-STABLE and with =
sys/powerpc/include/asm.h from 11.0-CURRENT as well). Both ofwcall64.S's =
work when this change is in place. My initial, special ofwcall code that =
I was using is not needed.
[Again: I only claim that the most frequent boot failure disappears and =
that I've not found any .got corruptions when the change is in place. =
Other far less frequent boot failures that I've historically reported =
backtraces for may well still happen.]
I only have access to PowerMac G5 powerpc64 contexts (11,2 and 7,2, 8G =
RAM, 12G RAM and 16G RAM examples) so I can not claim any wider range of =
appropriateness than PowerMac G5s, not even other AIM contexts (if any).
So to not change the behavior for other contexts: I do not know if there =
is a reasonable "IsPowerMac" test but conceptually if an official change =
for the improvement was to be made it would need such a live check for a =
generic build that was to span PowerMac G5s and other things. I would =
not presume to remove "mtsprg0 %1\n\t" for other contexts.
My experimental code just plugs in a constant for where the live =
IsPowerMac test could possibly be:
#if defined(AIM) && defined(__powerpc64__)
/* HACK: PowerMac G5 specific code to avoid demonstrated hangs in
* the early boot time frame.
* This would need a live test for PowerMac vs. not in order
* to remove HACK status.
*/
if (1)
__asm __volatile("mfsprg0 %0\n\t"
"mtsprg1 %1\n\t"
"mtsprg2 %2\n\t"
"mtsprg3 %3\n\t"
: "=3D&r"(ofw_sprg0_save)
: "r"(ofmsr[2]),
"r"(ofmsr[3]),
"r"(ofmsr[4]));
else
#endif
__asm __volatile("mfsprg0 %0\n\t"
"mtsprg0 %1\n\t"
"mtsprg1 %2\n\t"
"mtsprg2 %3\n\t"
"mtsprg3 %4\n\t"
: "=3D&r"(ofw_sprg0_save)
: "r"(ofmsr[1]),
"r"(ofmsr[2]),
"r"(ofmsr[3]),
"r"(ofmsr[4]));
But it also may be that there would be a desire to get the PowerMac =
specific code into sys/powerpc/powermac/... someplace.
I do hope that an official powerpc64 FreeBSD update for this can be made =
to help other PowerMac G5s boot more reliably.
Context details:
root@FBSDG5M1:/usr/src # freebsd-version -ku ; uname -a
10.1-STABLE
10.1-STABLE
FreeBSD FBSDG5M1 10.1-STABLE FreeBSD 10.1-STABLE #78 r279201M: Sat Feb =
28 22:54:30 PST 2015 =
root@FBSDG5M1:/usr/obj/usr/src/sys/GENERIC64vtsc powerpc
root@FBSDG5M1:/usr/src # svnlite info
Path: .
Working Copy Root Path: /usr/src
URL: https://svn0.us-west.freebsd.org/base/stable/10
Relative URL: ^/stable/10
Repository Root: https://svn0.us-west.freebsd.org/base
Repository UUID: ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
Revision: 279201
Node Kind: directory
Schedule: normal
Last Changed Author: pluknet
Last Changed Rev: 279201
Last Changed Date: 2015-02-23 00:45:42 -0800 (Mon, 23 Feb 2015)
root@FBSDG5M1:/usr/src # svnlite st
? .snap
M sys/ddb/db_main.c
M sys/ddb/db_script.c
M sys/powerpc/conf
? sys/powerpc/conf/GENERIC64vtsc
M sys/powerpc/ofw/ofw_machdep.c
M sys/powerpc/ofw/ofwcall64.S
The ddb/...'s and ofw/ofwcall64.S are changed only to allow reporting =
information for early failures as part of my investigation process (if =
any).
root@FBSDG5M1:/usr/src # more sys/powerpc/conf/GENERIC64vtsc=20
include GENERIC64
ident GENERIC64vtsc
nooptions PS3 #Sony Playstation 3 =
HACK!!! to allow sc
options DDB # HACK!!! to dump early crash =
info (but 11.0-CURRENT already has it)
options GDB # HACK!!! ...
#options VERBOSE_SYSINIT
#options BOOTVERBOSE=3D1
#options BOOTHOWTO=3DRB_VERBOSE
#options KTR
#options KTR_MASK=3DKTR_TRAP
#options KTR_CPUMASK=3D0xF
#options KTR_VERBOSE
# HACK!!! to allow sc for 2560x1440 display on Radeon X1950 that vt =
historically mishandled during booting
device sc
#device kbdmux # HACK: already listed by vt
options SC_OFWFB # OFW frame buffer
options SC_DFLT_FONT # compile font in
makeoptions SC_DFLT_FONT=3Dcp437
# Disable extra checking typically used for FreeBSD 11.0-CURRENT:
nooptions DEADLKRES #Enable the deadlock resolver
nooptions INVARIANTS #Enable calls of extra sanity =
checking
nooptions INVARIANT_SUPPORT #Extra sanity checks of internal =
structures, required by INVARIANTS
nooptions WITNESS #Enable checks to detect =
deadlocks and cycles
nooptions WITNESS_SKIPSPIN #Don't run witness on spinlocks =
for speed
nooptions MALLOC_DEBUG_MAXZONES # Separate malloc(9) zones
root@FBSDG5M1:/usr/src # more /etc/make.conf
WRKDIRPREFIX=3D/usr/obj/portswork
WITH_DEBUG=3D
MALLOC_PRODUCTION=3D
root@FBSDG5M1:/usr/src # more /etc/src.conf
#CFLAGS+=3D-DELF_VERBOSE
#WITH_DEBUG_FILES=3D
#WITHOUT_CLANG=3D
=3D=3D=3D
Mark Millard
markmi at dsl-only.net
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