On Mon, 2019-05-13 at 11:08 +0200, Christophe Leroy wrote:

Le 13/05/2019 à 09:17, Michael Neuling a écrit :

quoted

If you compile with KVM but without CONFIG_HAVE_HW_BREAKPOINT you fail
at linking with:
   arch/powerpc/kvm/book3s_hv_rmhandlers.o:(.text+0x708): undefined
reference to `dawr_force_enable'

This was caused by commit c1fe190c0672 ("powerpc: Add force enable of
DAWR on P9 option").

This puts more of the dawr infrastructure in a new file.

I think you are doing a bit more than that. I think you should explain 
that you define a new CONFIG_ option, when it is selected, etc ...

The commit you are referring to is talking about P9. It looks like your 
patch covers a lot more, so it should be mentionned her I guess.

Not really. It looks like I'm doing a lot but I'm really just moving code around
to deal with the ugliness of a bunch of config options and dependencies. 

quoted

Signed-off-by: Michael Neuling <redacted>

You should add a Fixes: tag, ie:

Fixes: c1fe190c0672 ("powerpc: Add force enable of DAWR on P9 option")

Ok

quoted

--
v2:
   Fixes based on Christophe Leroy's comments:
   - Fix commit message formatting
   - Move more DAWR code into dawr.c
---
  arch/powerpc/Kconfig                     |  5 ++
  arch/powerpc/include/asm/hw_breakpoint.h | 20 ++++---
  arch/powerpc/kernel/Makefile             |  1 +
  arch/powerpc/kernel/dawr.c               | 75 ++++++++++++++++++++++++
  arch/powerpc/kernel/hw_breakpoint.c      | 56 ------------------
  arch/powerpc/kvm/Kconfig                 |  1 +
  6 files changed, 94 insertions(+), 64 deletions(-)
  create mode 100644 arch/powerpc/kernel/dawr.c

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 2711aac246..f4b19e48cc 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig

@@ -242,6 +242,7 @@ config PPC
  	select SYSCTL_EXCEPTION_TRACE
  	select THREAD_INFO_IN_TASK
  	select VIRT_TO_BUS			if !PPC64
+	select PPC_DAWR_FORCE_ENABLE		if PPC64 || PERF

What's PERF ? Did you mean PERF_EVENTS ?

Then what you mean is:
- Selected all the time for PPC64
- Selected for PPC32 when PERF is also selected.

Is that what you want ? At first I thought it was linked to P9.

This is wrong.  I think we just want PPC64. PERF is a red herring.

And ... did you read below statement ?

Clearly not :-)

quoted

  	#
  	# Please keep this list sorted alphabetically.
  	#

@@ -369,6 +370,10 @@ config PPC_ADV_DEBUG_DAC_RANGE
  	depends on PPC_ADV_DEBUG_REGS && 44x
  	default y
  
+config PPC_DAWR_FORCE_ENABLE
+	bool
+	default y
+

Why defaulting it to y. Then how is it set to n ?

Good point.

quoted

  config ZONE_DMA
  	bool
  	default y if PPC_BOOK3E_64

diff --git a/arch/powerpc/include/asm/hw_breakpoint.h

b/arch/powerpc/include/asm/hw_breakpoint.h
index 0fe8c1e46b..ffbc8eab41 100644

--- a/arch/powerpc/include/asm/hw_breakpoint.h
+++ b/arch/powerpc/include/asm/hw_breakpoint.h

@@ -47,6 +47,8 @@ struct arch_hw_breakpoint {
  #define HW_BRK_TYPE_PRIV_ALL	(HW_BRK_TYPE_USER | HW_BRK_TYPE_KERNEL |

\
  				 HW_BRK_TYPE_HYP)
  
+extern int set_dawr(struct arch_hw_breakpoint *brk);
+
  #ifdef CONFIG_HAVE_HW_BREAKPOINT
  #include <linux/kdebug.h>
  #include <asm/reg.h>

@@ -90,18 +92,20 @@ static inline void hw_breakpoint_disable(void)
  extern void thread_change_pc(struct task_struct *tsk, struct pt_regs

*regs);
  int hw_breakpoint_handler(struct die_args *args);
  
-extern int set_dawr(struct arch_hw_breakpoint *brk);
-extern bool dawr_force_enable;
-static inline bool dawr_enabled(void)
-{
-	return dawr_force_enable;
-}
-

That's a very simple function, why not keep it here (or in another .h) 
as 'static inline' ?

Sure.

quoted

  #else	/* CONFIG_HAVE_HW_BREAKPOINT */
  static inline void hw_breakpoint_disable(void) { }
  static inline void thread_change_pc(struct task_struct *tsk,
  					struct pt_regs *regs) { }
-static inline bool dawr_enabled(void) { return false; }
+
  #endif	/* CONFIG_HAVE_HW_BREAKPOINT */
+
+extern bool dawr_force_enable;
+
+#ifdef CONFIG_PPC_DAWR_FORCE_ENABLE
+extern bool dawr_enabled(void);

Functions should not be 'extern'. I'm sure checkpatch --strict will tell 
you.

That's not what's currently being done in this header file.  I'm keeping with
the style of that file.

quoted

+#else
+#define dawr_enabled() true

true by default ?
Previously it was false by default.

Thanks, yeah that's wrong but I need to rethink the config option to make it
CONFIG_PPC_DAWR. 

This patch is far more difficult than it should be due to the mess that
CONFIG_HAVE_HW_BREAKPOINT and CONFIG_PPC_ADV_DEBUG_REGS creates in ptrace.c and
process.c. We really need to fix up 
https://github.com/linuxppc/issues/issues/128

And why a #define ? That's better to keep a static inline.

Changed.

quoted

+#endif
+
  #endif	/* __KERNEL__ */
  #endif	/* _PPC_BOOK3S_64_HW_BREAKPOINT_H */

diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 0ea6c4aa3a..a9c497c34f 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile

@@ -56,6 +56,7 @@ obj-$(CONFIG_PPC64)		+= setup_64.o

sys_ppc32.o \
  obj-$(CONFIG_VDSO32)		+= vdso32/
  obj-$(CONFIG_PPC_WATCHDOG)	+= watchdog.o
  obj-$(CONFIG_HAVE_HW_BREAKPOINT)	+= hw_breakpoint.o
+obj-$(CONFIG_PPC_DAWR_FORCE_ENABLE)	+= dawr.o
  obj-$(CONFIG_PPC_BOOK3S_64)	+= cpu_setup_ppc970.o cpu_setup_pa6t.o
  obj-$(CONFIG_PPC_BOOK3S_64)	+= cpu_setup_power.o
  obj-$(CONFIG_PPC_BOOK3S_64)	+= mce.o mce_power.o

diff --git a/arch/powerpc/kernel/dawr.c b/arch/powerpc/kernel/dawr.c
new file mode 100644
index 0000000000..cf1d02fe1e
--- /dev/null
+++ b/arch/powerpc/kernel/dawr.c

@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// DAWR infrastructure
+//
+// Copyright 2019, Michael Neuling, IBM Corporation.
+
+#include <linux/types.h>
+#include <linux/export.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <asm/debugfs.h>
+#include <asm/machdep.h>
+#include <asm/hvcall.h>
+
+bool dawr_force_enable;
+EXPORT_SYMBOL_GPL(dawr_force_enable);
+
+extern bool dawr_enabled(void)

extern ????

oops

quoted

+{
+	return dawr_force_enable;
+}
+EXPORT_SYMBOL_GPL(dawr_enabled);

Since dawr_force_enable is also exported, I see no point in having such 
a tiny function as an exported function, was better as a 'static inline'.

Yep, changed to static inline.

quoted

+
+static ssize_t dawr_write_file_bool(struct file *file,
+				    const char __user *user_buf,
+				    size_t count, loff_t *ppos)
+{
+	struct arch_hw_breakpoint null_brk = {0, 0, 0};
+	size_t rc;
+
+	/* Send error to user if they hypervisor won't allow us to write DAWR */
+	if ((!dawr_force_enable) &&
+	    (firmware_has_feature(FW_FEATURE_LPAR)) &&
+	    (set_dawr(&null_brk) != H_SUCCESS))

The above is not real clear.
set_dabr() returns 0, H_SUCCESS is not used there.

It pseries_set_dawr() will return a hcall number.

This code hasn't changed. I'm just moving it.

quoted

+		return -1;
+
+	rc = debugfs_write_file_bool(file, user_buf, count, ppos);
+	if (rc)
+		return rc;
+
+	/* If we are clearing, make sure all CPUs have the DAWR cleared */
+	if (!dawr_force_enable)
+		smp_call_function((smp_call_func_t)set_dawr, &null_brk, 0);
+
+	return rc;
+}
+
+static const struct file_operations dawr_enable_fops = {
+	.read =		debugfs_read_file_bool,
+	.write =	dawr_write_file_bool,
+	.open =		simple_open,
+	.llseek =	default_llseek,
+};
+
+static int __init dawr_force_setup(void)
+{
+	dawr_force_enable = false;

The above is not needed, the BSS is zeroised at kernel startup.

quoted

+
+	if (cpu_has_feature(CPU_FTR_DAWR)) {
+		/* Don't setup sysfs file for user control on P8 */
+		dawr_force_enable = true;

Strange comment, word "don't" doesn't really fit with a 'true'

quoted

+		return 0;
+	}
+
+	if (PVR_VER(mfspr(SPRN_PVR)) == PVR_POWER9) {

You could use pvr_version_is(PVR_POWER9) instead of open codiing.

All this code hasn't changed. I'm just moving it.

Feel free to clean it up but lets fix a real problem here.

quoted

+		/* Turn DAWR off by default, but allow admin to turn it on */
+		dawr_force_enable = false;
+		debugfs_create_file_unsafe("dawr_enable_dangerous", 0600,
+					   powerpc_debugfs_root,
+					   &dawr_force_enable,
+					   &dawr_enable_fops);
+	}
+	return 0;
+}
+arch_initcall(dawr_force_setup);

Wouldn't it also make sense to move set_dawr() from process.c to here ?

Yep, done.

quoted

diff --git a/arch/powerpc/kernel/hw_breakpoint.c

b/arch/powerpc/kernel/hw_breakpoint.c
index da307dd93e..95605a9c9a 100644

--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c

@@ -380,59 +380,3 @@ void hw_breakpoint_pmu_read(struct perf_event *bp)
  {
  	/* TODO */
  }
-
-bool dawr_force_enable;
-EXPORT_SYMBOL_GPL(dawr_force_enable);
-
-static ssize_t dawr_write_file_bool(struct file *file,
-				    const char __user *user_buf,
-				    size_t count, loff_t *ppos)
-{
-	struct arch_hw_breakpoint null_brk = {0, 0, 0};
-	size_t rc;
-
-	/* Send error to user if they hypervisor won't allow us to write DAWR */
-	if ((!dawr_force_enable) &&
-	    (firmware_has_feature(FW_FEATURE_LPAR)) &&
-	    (set_dawr(&null_brk) != H_SUCCESS))
-		return -1;
-
-	rc = debugfs_write_file_bool(file, user_buf, count, ppos);
-	if (rc)
-		return rc;
-
-	/* If we are clearing, make sure all CPUs have the DAWR cleared */
-	if (!dawr_force_enable)
-		smp_call_function((smp_call_func_t)set_dawr, &null_brk, 0);
-
-	return rc;
-}
-
-static const struct file_operations dawr_enable_fops = {
-	.read =		debugfs_read_file_bool,
-	.write =	dawr_write_file_bool,
-	.open =		simple_open,
-	.llseek =	default_llseek,
-};
-
-static int __init dawr_force_setup(void)
-{
-	dawr_force_enable = false;
-
-	if (cpu_has_feature(CPU_FTR_DAWR)) {
-		/* Don't setup sysfs file for user control on P8 */
-		dawr_force_enable = true;
-		return 0;
-	}
-
-	if (PVR_VER(mfspr(SPRN_PVR)) == PVR_POWER9) {
-		/* Turn DAWR off by default, but allow admin to turn it on */
-		dawr_force_enable = false;
-		debugfs_create_file_unsafe("dawr_enable_dangerous", 0600,
-					   powerpc_debugfs_root,
-					   &dawr_force_enable,
-					   &dawr_enable_fops);
-	}
-	return 0;
-}
-arch_initcall(dawr_force_setup);

diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
index bfdde04e49..9c0d315108 100644
--- a/arch/powerpc/kvm/Kconfig
+++ b/arch/powerpc/kvm/Kconfig

@@ -39,6 +39,7 @@ config KVM_BOOK3S_32_HANDLER
  config KVM_BOOK3S_64_HANDLER
  	bool
  	select KVM_BOOK3S_HANDLER
+	select PPC_DAWR_FORCE_ENABLE
  
  config KVM_BOOK3S_PR_POSSIBLE
  	bool

Christophe