Re: [PATCH 2/3] powerpc: fix regression of per-CPU DSCR setting
On Wednesday 21 May 2014 12:02 PM, Sam Bobroff wrote:
Since commit efcac65 powerpc: Per process DSCR + some fixes (try#4)
it is no longer possible to set the DSCR on a per-CPU basis.
The old behaviour was to minipulate the DSCR SPR directly but this is no
longer sufficient: the value is quickly overwritten by context switching.
This patch stores the per-CPU DSCR value in a kernel variable rather than
directly in the SPR and it is used whenever a process has not set the DSCR
itself. The sysfs interface (/sys/devices/system/cpu/cpuN/dscr) is unchanged.
Writes to the old global default (/sys/devices/system/cpu/dscr_default)
now set all of the per-CPU values and reads return the last written value.
The new per-CPU default is added to the paca_struct and is used everywhere
outside of sysfs.c instead of the old global default.
Signed-off-by: Sam Bobroff sam.bobr...@au1.ibm.com
---
arch/powerpc/include/asm/paca.h |3 +++
arch/powerpc/kernel/asm-offsets.c |1 +
arch/powerpc/kernel/entry_64.S |9 +
arch/powerpc/kernel/sysfs.c | 32
++-
arch/powerpc/kernel/tm.S| 16
arch/powerpc/kvm/book3s_hv_rmhandlers.S |3 +--
6 files changed, 29 insertions(+), 35 deletions(-)
diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index 8e956a0..bb0bd25 100644
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -92,7 +92,10 @@ struct paca_struct {
struct slb_shadow *slb_shadow_ptr;
struct dtl_entry *dispatch_log;
struct dtl_entry *dispatch_log_end;
+#endif /* CONFIG_PPC_STD_MMU_64 */
+ u64 dscr_default; /* per-CPU default DSCR */
+#ifdef CONFIG_PPC_STD_MMU_64
/*
* Now, starting in cacheline 2, the exception save areas
*/
diff --git a/arch/powerpc/kernel/asm-offsets.c
b/arch/powerpc/kernel/asm-offsets.c
index dba8140..cba2697 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -247,6 +247,7 @@ int main(void)
#endif
DEFINE(PACAHWCPUID, offsetof(struct paca_struct, hw_cpu_id));
DEFINE(PACAKEXECSTATE, offsetof(struct paca_struct, kexec_state));
+ DEFINE(PACA_DSCR, offsetof(struct paca_struct, dscr_default));
DEFINE(PACA_STARTTIME, offsetof(struct paca_struct, starttime));
DEFINE(PACA_STARTTIME_USER, offsetof(struct paca_struct,
starttime_user));
DEFINE(PACA_USER_TIME, offsetof(struct paca_struct, user_time));
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 9fde8a1..911d453 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -387,12 +387,6 @@ _GLOBAL(ret_from_kernel_thread)
li r3,0
b syscall_exit
- .section.toc,aw
-DSCR_DEFAULT:
- .tc dscr_default[TC],dscr_default
-
- .section.text
-
/*
* This routine switches between two different tasks. The process
* state of one is saved on its kernel stack. Then the state
@@ -577,11 +571,10 @@ END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
#ifdef CONFIG_PPC64
BEGIN_FTR_SECTION
lwz r6,THREAD_DSCR_INHERIT(r4)
- ld r7,DSCR_DEFAULT@toc(2)
ld r0,THREAD_DSCR(r4)
cmpwi r6,0
bne 1f
- ld r0,0(r7)
+ ld r0,PACA_DSCR(r13)
1:
BEGIN_FTR_SECTION_NESTED(70)
mfspr r8, SPRN_FSCR
diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
index e2a1d6f..67fd2fd 100644
--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c
@@ -484,7 +484,6 @@ SYSFS_PMCSETUP(pmc8, SPRN_PMC8);
SYSFS_PMCSETUP(mmcra, SPRN_MMCRA);
SYSFS_SPRSETUP(purr, SPRN_PURR);
SYSFS_SPRSETUP(spurr, SPRN_SPURR);
-SYSFS_SPRSETUP(dscr, SPRN_DSCR);
SYSFS_SPRSETUP(pir, SPRN_PIR);
/*
@@ -494,12 +493,27 @@ SYSFS_SPRSETUP(pir, SPRN_PIR);
*/
static DEVICE_ATTR(mmcra, 0600, show_mmcra, store_mmcra);
static DEVICE_ATTR(spurr, 0400, show_spurr, NULL);
-static DEVICE_ATTR(dscr, 0600, show_dscr, store_dscr);
static DEVICE_ATTR(purr, 0400, show_purr, store_purr);
static DEVICE_ATTR(pir, 0400, show_pir, NULL);
-unsigned long dscr_default = 0;
-EXPORT_SYMBOL(dscr_default);
+static unsigned long dscr_default;
+
+static void read_dscr(void *val)
+{
+ *(unsigned long *)val = get_paca()-dscr_default;
+}
+
+static void write_dscr(void *val)
+{
+ get_paca()-dscr_default = *(unsigned long *)val;
+ if (!current-thread.dscr_inherit) {
+ current-thread.dscr = *(unsigned long *)val;
+ mtspr(SPRN_DSCR, *(unsigned long *)val);
+ }
+}
+
+SYSFS_SPRSETUP_SHOW_STORE(dscr);
+static DEVICE_ATTR(dscr, 0600, show_dscr, store_dscr);
static void add_write_permission_dev_attr(struct device_attribute *attr)
{
@@ -512,14 +526,6 @@ static ssize_t show_dscr_default(struct device *dev,
[PATCH 2/3] powerpc: fix regression of per-CPU DSCR setting
Since commit efcac65 powerpc: Per process DSCR + some fixes (try#4)
it is no longer possible to set the DSCR on a per-CPU basis.
The old behaviour was to minipulate the DSCR SPR directly but this is no
longer sufficient: the value is quickly overwritten by context switching.
This patch stores the per-CPU DSCR value in a kernel variable rather than
directly in the SPR and it is used whenever a process has not set the DSCR
itself. The sysfs interface (/sys/devices/system/cpu/cpuN/dscr) is unchanged.
Writes to the old global default (/sys/devices/system/cpu/dscr_default)
now set all of the per-CPU values and reads return the last written value.
The new per-CPU default is added to the paca_struct and is used everywhere
outside of sysfs.c instead of the old global default.
Signed-off-by: Sam Bobroff sam.bobr...@au1.ibm.com
---
arch/powerpc/include/asm/paca.h |3 +++
arch/powerpc/kernel/asm-offsets.c |1 +
arch/powerpc/kernel/entry_64.S |9 +
arch/powerpc/kernel/sysfs.c | 32 ++-
arch/powerpc/kernel/tm.S| 16
arch/powerpc/kvm/book3s_hv_rmhandlers.S |3 +--
6 files changed, 29 insertions(+), 35 deletions(-)
diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index 8e956a0..bb0bd25 100644
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -92,7 +92,10 @@ struct paca_struct {
struct slb_shadow *slb_shadow_ptr;
struct dtl_entry *dispatch_log;
struct dtl_entry *dispatch_log_end;
+#endif /* CONFIG_PPC_STD_MMU_64 */
+ u64 dscr_default; /* per-CPU default DSCR */
+#ifdef CONFIG_PPC_STD_MMU_64
/*
* Now, starting in cacheline 2, the exception save areas
*/
diff --git a/arch/powerpc/kernel/asm-offsets.c
b/arch/powerpc/kernel/asm-offsets.c
index dba8140..cba2697 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -247,6 +247,7 @@ int main(void)
#endif
DEFINE(PACAHWCPUID, offsetof(struct paca_struct, hw_cpu_id));
DEFINE(PACAKEXECSTATE, offsetof(struct paca_struct, kexec_state));
+ DEFINE(PACA_DSCR, offsetof(struct paca_struct, dscr_default));
DEFINE(PACA_STARTTIME, offsetof(struct paca_struct, starttime));
DEFINE(PACA_STARTTIME_USER, offsetof(struct paca_struct,
starttime_user));
DEFINE(PACA_USER_TIME, offsetof(struct paca_struct, user_time));
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 9fde8a1..911d453 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -387,12 +387,6 @@ _GLOBAL(ret_from_kernel_thread)
li r3,0
b syscall_exit
- .section.toc,aw
-DSCR_DEFAULT:
- .tc dscr_default[TC],dscr_default
-
- .section.text
-
/*
* This routine switches between two different tasks. The process
* state of one is saved on its kernel stack. Then the state
@@ -577,11 +571,10 @@ END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
#ifdef CONFIG_PPC64
BEGIN_FTR_SECTION
lwz r6,THREAD_DSCR_INHERIT(r4)
- ld r7,DSCR_DEFAULT@toc(2)
ld r0,THREAD_DSCR(r4)
cmpwi r6,0
bne 1f
- ld r0,0(r7)
+ ld r0,PACA_DSCR(r13)
1:
BEGIN_FTR_SECTION_NESTED(70)
mfspr r8, SPRN_FSCR
diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
index e2a1d6f..67fd2fd 100644
--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c
@@ -484,7 +484,6 @@ SYSFS_PMCSETUP(pmc8, SPRN_PMC8);
SYSFS_PMCSETUP(mmcra, SPRN_MMCRA);
SYSFS_SPRSETUP(purr, SPRN_PURR);
SYSFS_SPRSETUP(spurr, SPRN_SPURR);
-SYSFS_SPRSETUP(dscr, SPRN_DSCR);
SYSFS_SPRSETUP(pir, SPRN_PIR);
/*
@@ -494,12 +493,27 @@ SYSFS_SPRSETUP(pir, SPRN_PIR);
*/
static DEVICE_ATTR(mmcra, 0600, show_mmcra, store_mmcra);
static DEVICE_ATTR(spurr, 0400, show_spurr, NULL);
-static DEVICE_ATTR(dscr, 0600, show_dscr, store_dscr);
static DEVICE_ATTR(purr, 0400, show_purr, store_purr);
static DEVICE_ATTR(pir, 0400, show_pir, NULL);
-unsigned long dscr_default = 0;
-EXPORT_SYMBOL(dscr_default);
+static unsigned long dscr_default;
+
+static void read_dscr(void *val)
+{
+ *(unsigned long *)val = get_paca()-dscr_default;
+}
+
+static void write_dscr(void *val)
+{
+ get_paca()-dscr_default = *(unsigned long *)val;
+ if (!current-thread.dscr_inherit) {
+ current-thread.dscr = *(unsigned long *)val;
+ mtspr(SPRN_DSCR, *(unsigned long *)val);
+ }
+}
+
+SYSFS_SPRSETUP_SHOW_STORE(dscr);
+static DEVICE_ATTR(dscr, 0600, show_dscr, store_dscr);
static void add_write_permission_dev_attr(struct device_attribute *attr)
{
@@ -512,14 +526,6 @@ static ssize_t show_dscr_default(struct device *dev,
return sprintf(buf, %lx\n, dscr_default);
}
-static void update_dscr(void *dummy)
-{
- if
