[PATCH] [MIPS] Add fix for loongson3 llsc errata

[Jiaxun Yang]

This patch adds fix for Loongson-3 llsc errata.

/gas
* config/tc-mips.c (mips_fix_loongson3_llsc): New variables.
(md_loongopts): Add New options -mfix-loongson3-llsc,
-mno-fix-loongson3-llsc.
(md_parse_option): Initialize variables via above options.
(options): New enums for the above options.
(md_assemble): Insert sync before ll/lld if fix enabled.
* doc/c-mips.texi Document the -mfix-loongson3-llsc.
* testsuit/gas/mips/loongson3a-4.d New.
* testsuit/gas/mips/loongson3a-4.s New.
---
gas/config/tc-mips.c | 55 ++++++++++++++++++++++++++++++++--
gas/doc/c-mips.texi | 6 ++++
gas/testsuite/gas/mips/loongson-3a-4.d | 18 +++++++++++
gas/testsuite/gas/mips/loongson-3a-4.s | 8 +++++
4 files changed, 85 insertions(+), 2 deletions(-)
create mode 100644 gas/testsuite/gas/mips/loongson-3a-4.d
create mode 100644 gas/testsuite/gas/mips/loongson-3a-4.s

diff --git a/gas/config/tc-mips.c b/gas/config/tc-mips.c
index 97c9109c4f..0b2101e728 100644
--- a/gas/config/tc-mips.c
+++ b/gas/config/tc-mips.c
@@ -917,6 +917,9 @@ static bfd_boolean mips_fix_loongson2f_nop;
/* True if -mfix-loongson2f-nop or -mfix-loongson2f-jump passed. */
static bfd_boolean mips_fix_loongson2f;

+/* ...likewise -mfix-loongson3-llsc. */
+ static bfd_boolean mips_fix_loongson3_llsc = TRUE;
+
/* Given two FIX_VR4120_* values X and Y, bit Y of element X is set if
there must be at least one other instruction between an instruction
of type X and an instruction of type Y. */
@@ -1479,6 +1482,8 @@ enum options
OPTION_NO_FIX_LOONGSON2F_JUMP,
OPTION_FIX_LOONGSON2F_NOP,
OPTION_NO_FIX_LOONGSON2F_NOP,
+ OPTION_FIX_LOONGSON3_LLSC,
+ OPTION_NO_FIX_LOONGSON3_LLSC,
OPTION_FIX_VR4120,
OPTION_NO_FIX_VR4120,
OPTION_FIX_VR4130,
@@ -1601,6 +1606,8 @@ struct option md_longopts[] =
{"mno-fix-loongson2f-jump", no_argument, NULL, OPTION_NO_FIX_LOONGSON2F_JUMP},
{"mfix-loongson2f-nop", no_argument, NULL, OPTION_FIX_LOONGSON2F_NOP},
{"mno-fix-loongson2f-nop", no_argument, NULL, OPTION_NO_FIX_LOONGSON2F_NOP},
+ {"mfix-loongson3-llsc", no_argument, NULL, OPTION_FIX_LOONGSON3_LLSC},
+ {"mno-fix-loongson3-llsc", no_argument, NULL, OPTION_NO_FIX_LOONGSON3_LLSC},
{"mfix-vr4120", no_argument, NULL, OPTION_FIX_VR4120},
{"mno-fix-vr4120", no_argument, NULL, OPTION_NO_FIX_VR4120},
{"mfix-vr4130", no_argument, NULL, OPTION_FIX_VR4130},
@@ -4126,8 +4133,43 @@ md_assemble (char *str)
}

if (insn_error.msg)
- report_insn_error (str);
- else if (insn.insn_mo->pinfo == INSN_MACRO)
+ {
+ report_insn_error (str);
+ goto out;
+ }
+
+ if (mips_fix_loongson3_llsc)
+ {
+ static expressionS bak_imm_expr;
+ static expressionS bak_offset_expr;
+ static bfd_reloc_code_real_type bak_offset_reloc[3] ;
+
+ struct insn_label_list *is_label;
+ is_label = seg_info (now_seg)->label_list;
+
+ if (((strcmp (insn.insn_mo->name, "ll") == 0)
+ ||(strcmp (insn.insn_mo->name, "lld") == 0))
+ && (strcmp (history[0].insn_mo->name, "sync") || is_label))
+ {
+ bak_imm_expr = imm_expr;
+ bak_offset_expr = offset_expr;
+
+ bak_offset_reloc[0] = offset_reloc[0];
+ bak_offset_reloc[1] = offset_reloc[1];
+ bak_offset_reloc[2] = offset_reloc[2];
+
+ md_assemble ((char *) "sync");
+
+ imm_expr = bak_imm_expr;
+ offset_expr = bak_offset_expr;
+
+ offset_reloc[0] = bak_offset_reloc[0];
+ offset_reloc[1] = bak_offset_reloc[1];
+ offset_reloc[2] = bak_offset_reloc[2];
+ }
+ }
+
+ if (insn.insn_mo->pinfo == INSN_MACRO)
{
macro_start ();
if (mips_opts.mips16)
@@ -4144,6 +4186,7 @@ md_assemble (char *str)
append_insn (&insn, NULL, unused_reloc, FALSE);
}

+out:
mips_assembling_insn = FALSE;
}

@@ -14652,6 +14695,14 @@ md_parse_option (int c, const char *arg)
mips_fix_loongson2f_nop = FALSE;
break;

+ case OPTION_FIX_LOONGSON3_LLSC:
+ mips_fix_loongson3_llsc = TRUE;
+ break;
+
+ case OPTION_NO_FIX_LOONGSON3_LLSC:
+ mips_fix_loongson3_llsc = FALSE;
+ break;
+
case OPTION_FIX_VR4120:
mips_fix_vr4120 = 1;
break;
diff --git a/gas/doc/c-mips.texi b/gas/doc/c-mips.texi
index 083b24d70b..2da6b8ca9c 100644
--- a/gas/doc/c-mips.texi
+++ b/gas/doc/c-mips.texi
@@ -268,6 +268,12 @@ Replace nops by @code{or at,at,zero} to work around the Loongson2F
deadlock. The issue has been solved in later Loongson2F batches, but
this fix has no side effect to them.

+@item -mfix-loongson3-llsc
+@itemx -mno-fix-loongson3-llsc
+Insert @code{sync} instruction before @samp{ll} or @samp{lld} instrction
+to work around Loongson3 @samp{LL}/@samp{SC} errata.
+This issue exists in all Loongson3 CPUs.
+
@item -mfix-vr4120
@itemx -mno-fix-vr4120
Insert nops to work around certain VR4120 errata. This option is
diff --git a/gas/testsuite/gas/mips/loongson-3a-4.d b/gas/testsuite/gas/mips/loongson-3a-4.d
new file mode 100644
index 0000000000..ca7e16f9b1
--- /dev/null
+++ b/gas/testsuite/gas/mips/loongson-3a-4.d
@@ -0,0 +1,18 @@
+#as: -march=loongson3a -mabi=n64 -mfix-loongson3-llsc
+#objdump: -M reg-names=numeric -dr
+#name: Loongson3 LLSC fix test
+
+.*: file format .*
+
+Disassembly of section .text:
+
+[0-9a-f]+ <.text>:
+.*: 0000000f sync
+.*: c3a80010 ll t0,16(sp)
+.*: 0000000f sync
+.*: c3a80010 ll t0,16(sp)
+.*: 0000000f sync
+.*: c3a80010 lld t0,16(sp)
+.*: 0000000f sync
+.*: c3a80010 lld t0,16(sp)
+#pass
\ No newline at end of file
diff --git a/gas/testsuite/gas/mips/loongson-3a-4.s b/gas/testsuite/gas/mips/loongson-3a-4.s
new file mode 100644
index 0000000000..fa7e26a8dc
--- /dev/null
+++ b/gas/testsuite/gas/mips/loongson-3a-4.s
@@ -0,0 +1,8 @@
+# Test the work around of the LLSC issue of Loongson3
+
+ll $t0, 16($sp)
+sync
+ll $t0, 16($sp)
+lld $t0, 16($sp)
+sync
+lld $t0, 16($sp)
\ No newline at end of file

[Matthew Fortune]

Post by Jiaxun Yang
+/* ...likewise -mfix-loongson3-llsc. */
+ static bfd_boolean mips_fix_loongson3_llsc = TRUE;
+

Just a brief comment... you are asking here for all code generation
for all cores to pay the penalty of the loongson errata by enabling
this by default.

You will probably need to enable it (if not explicitly disabled)
for just the loongson cores when targeted with -march. If you are
aiming for this to be enabled in a linux distro such as debian or
fedora so that all base packages are safe then you may need a
configure time option to enable this by default (if the distro
maintainer chooses to do so).

I have not looked at the implementation just noticed the default
effect being undesirable.

Hope that makes sense.

Thanks,
Matthew

[Jiaxun Yang]

This patch adds fix for Loongson-3 llsc errata.

/gas
* config/tc-mips.c (mips_fix_loongson3_llsc): New variables.
(md_loongopts): Add New options -mfix-loongson3-llsc,
-mno-fix-loongson3-llsc.
(md_parse_option): Initialize variables via above options.
(options): New enums for the above options.
(md_assemble): Insert sync before ll/lld if fix enabled.
* doc/c-mips.texi Document the -mfix-loongson3-llsc.
* testsuit/gas/mips/loongson3a-4.d New.
* testsuit/gas/mips/loongson3a-4.s New.
---
gas/config/tc-mips.c | 55 ++++++++++++++++++++++++++++++++--
gas/doc/c-mips.texi | 6 ++++
gas/testsuite/gas/mips/loongson-3a-4.d | 18 +++++++++++
gas/testsuite/gas/mips/loongson-3a-4.s | 8 +++++
4 files changed, 85 insertions(+), 2 deletions(-)
create mode 100644 gas/testsuite/gas/mips/loongson-3a-4.d
create mode 100644 gas/testsuite/gas/mips/loongson-3a-4.s

diff --git a/gas/config/tc-mips.c b/gas/config/tc-mips.c
index 97c9109c4f..0b2101e728 100644
--- a/gas/config/tc-mips.c
+++ b/gas/config/tc-mips.c
@@ -917,6 +917,9 @@ static bfd_boolean mips_fix_loongson2f_nop;
/* True if -mfix-loongson2f-nop or -mfix-loongson2f-jump passed. */
static bfd_boolean mips_fix_loongson2f;

+/* ...likewise -mfix-loongson3-llsc. */
+ static bfd_boolean mips_fix_loongson3_llsc;
+
/* Given two FIX_VR4120_* values X and Y, bit Y of element X is set if
there must be at least one other instruction between an instruction
of type X and an instruction of type Y. */
@@ -1479,6 +1482,8 @@ enum options
OPTION_NO_FIX_LOONGSON2F_JUMP,
OPTION_FIX_LOONGSON2F_NOP,
OPTION_NO_FIX_LOONGSON2F_NOP,
+ OPTION_FIX_LOONGSON3_LLSC,
+ OPTION_NO_FIX_LOONGSON3_LLSC,
OPTION_FIX_VR4120,
OPTION_NO_FIX_VR4120,
OPTION_FIX_VR4130,
@@ -1601,6 +1606,8 @@ struct option md_longopts[] =
{"mno-fix-loongson2f-jump", no_argument, NULL, OPTION_NO_FIX_LOONGSON2F_JUMP},
{"mfix-loongson2f-nop", no_argument, NULL, OPTION_FIX_LOONGSON2F_NOP},
{"mno-fix-loongson2f-nop", no_argument, NULL, OPTION_NO_FIX_LOONGSON2F_NOP},
+ {"mfix-loongson3-llsc", no_argument, NULL, OPTION_FIX_LOONGSON3_LLSC},
+ {"mno-fix-loongson3-llsc", no_argument, NULL, OPTION_NO_FIX_LOONGSON3_LLSC},
{"mfix-vr4120", no_argument, NULL, OPTION_FIX_VR4120},
{"mno-fix-vr4120", no_argument, NULL, OPTION_NO_FIX_VR4120},
{"mfix-vr4130", no_argument, NULL, OPTION_FIX_VR4130},
@@ -4126,8 +4133,43 @@ md_assemble (char *str)
}

if (insn_error.msg)
- report_insn_error (str);
- else if (insn.insn_mo->pinfo == INSN_MACRO)
+ {
+ report_insn_error (str);
+ goto out;
+ }
+
+ if (mips_fix_loongson3_llsc)
+ {
+ static expressionS bak_imm_expr;
+ static expressionS bak_offset_expr;
+ static bfd_reloc_code_real_type bak_offset_reloc[3] ;
+
+ struct insn_label_list *is_label;
+ is_label = seg_info (now_seg)->label_list;
+
+ if (((strcmp (insn.insn_mo->name, "ll") == 0)
+ ||(strcmp (insn.insn_mo->name, "lld") == 0))
+ && (strcmp (history[0].insn_mo->name, "sync") || is_label))
+ {
+ bak_imm_expr = imm_expr;
+ bak_offset_expr = offset_expr;
+
+ bak_offset_reloc[0] = offset_reloc[0];
+ bak_offset_reloc[1] = offset_reloc[1];
+ bak_offset_reloc[2] = offset_reloc[2];
+
+ md_assemble ((char *) "sync");
+
+ imm_expr = bak_imm_expr;
+ offset_expr = bak_offset_expr;
+
+ offset_reloc[0] = bak_offset_reloc[0];
+ offset_reloc[1] = bak_offset_reloc[1];
+ offset_reloc[2] = bak_offset_reloc[2];
+ }
+ }
+
+ if (insn.insn_mo->pinfo == INSN_MACRO)
{
macro_start ();
if (mips_opts.mips16)
@@ -4144,6 +4186,7 @@ md_assemble (char *str)
append_insn (&insn, NULL, unused_reloc, FALSE);
}

+out:
mips_assembling_insn = FALSE;
}

@@ -14652,6 +14695,14 @@ md_parse_option (int c, const char *arg)
mips_fix_loongson2f_nop = FALSE;
break;

+ case OPTION_FIX_LOONGSON3_LLSC:
+ mips_fix_loongson3_llsc = TRUE;
+ break;
+
+ case OPTION_NO_FIX_LOONGSON3_LLSC:
+ mips_fix_loongson3_llsc = FALSE;
+ break;
+
case OPTION_FIX_VR4120:
mips_fix_vr4120 = 1;
break;
diff --git a/gas/doc/c-mips.texi b/gas/doc/c-mips.texi
index 083b24d70b..2da6b8ca9c 100644
--- a/gas/doc/c-mips.texi
+++ b/gas/doc/c-mips.texi
@@ -268,6 +268,12 @@ Replace nops by @code{or at,at,zero} to work around the Loongson2F
deadlock. The issue has been solved in later Loongson2F batches, but
this fix has no side effect to them.

+@item -mfix-loongson3-llsc
+@itemx -mno-fix-loongson3-llsc
+Insert @code{sync} instruction before @samp{ll} or @samp{lld} instrction
+to work around Loongson3 @samp{LL}/@samp{SC} errata.
+This issue exists in all Loongson3 CPUs.
+
@item -mfix-vr4120
@itemx -mno-fix-vr4120
Insert nops to work around certain VR4120 errata. This option is
diff --git a/gas/testsuite/gas/mips/loongson-3a-4.d b/gas/testsuite/gas/mips/loongson-3a-4.d
new file mode 100644
index 0000000000..ca7e16f9b1
--- /dev/null
+++ b/gas/testsuite/gas/mips/loongson-3a-4.d
@@ -0,0 +1,18 @@
+#as: -march=loongson3a -mabi=n64 -mfix-loongson3-llsc
+#objdump: -M reg-names=numeric -dr
+#name: Loongson3 LLSC fix test
+
+.*: file format .*
+
+Disassembly of section .text:
+
+[0-9a-f]+ <.text>:
+.*: 0000000f sync
+.*: c3a80010 ll t0,16(sp)
+.*: 0000000f sync
+.*: c3a80010 ll t0,16(sp)
+.*: 0000000f sync
+.*: c3a80010 lld t0,16(sp)
+.*: 0000000f sync
+.*: c3a80010 lld t0,16(sp)
+#pass
\ No newline at end of file
diff --git a/gas/testsuite/gas/mips/loongson-3a-4.s b/gas/testsuite/gas/mips/loongson-3a-4.s
new file mode 100644
index 0000000000..fa7e26a8dc
--- /dev/null
+++ b/gas/testsuite/gas/mips/loongson-3a-4.s
@@ -0,0 +1,8 @@
+# Test the work around of the LLSC issue of Loongson3
+
+ll $t0, 16($sp)
+sync
+ll $t0, 16($sp)
+lld $t0, 16($sp)
+sync
+lld $t0, 16($sp)
\ No newline at end of file

[James Cowgill]

Hi,

Post by Jiaxun Yang
This patch adds fix for Loongson-3 llsc errata.
/gas
* config/tc-mips.c (mips_fix_loongson3_llsc): New variables.
(md_loongopts): Add New options -mfix-loongson3-llsc,
-mno-fix-loongson3-llsc.
(md_parse_option): Initialize variables via above options.
(options): New enums for the above options.
(md_assemble): Insert sync before ll/lld if fix enabled.
* doc/c-mips.texi Document the -mfix-loongson3-llsc.
* testsuit/gas/mips/loongson3a-4.d New.
* testsuit/gas/mips/loongson3a-4.s New.

I'm interested to know what this errata is. Why do you need the extra
sync and what does it do?

Some time ago, I also noticed a kernel patch was submitted to do
something similar in their atomic routines. The patch also adds a sync
after some sc instructions as well. Is that not necessary?

https://patchwork.linux-mips.org/patch/16987/

Thanks,
James

[Jiaxun Yang]

圚 2018-01-26五的 10:54 +0000James Cowgill写道

Post by James Cowgill
I'm interested to know what this errata is. Why do you need the extra
sync and what does it do?
Some time ago, I also noticed a kernel patch was submitted to do
something similar in their atomic routines. The patch also adds a sync
after some sc instructions as well. Is that not necessary?
https://patchwork.linux-mips.org/patch/16987/

Hi James

I'm not a hardware engineer and also not a loongson stuff so it's hard
for me to say why the errata happen.

I simply translate the errata part of Loongson 3A3000 processor user
manual[1] into English.

There are some strict limitations on loongson processors' ll/sc
instructions. If you don't respect these limitations carefully, it will
cause data corruption.

You should follow following rules when you're using ll/sc instructions.
1: There must be a sync instruction before any ll instruction
2: If there is a jump (such as j, jr or jal) instruction (such as j, jr
or jal) between ll instruction and sc instruction, then the target of
jump instruction must be a sync instruction.

And according to my tests, these limitations are necessary, or system
may freeze during SpinLock.

--
Jiaxun Yang