iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

powerpc: Fix regression of per-CPU DSCR setting

Browse Source 
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.bobroff@au1.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Sam bobroff 2014-05-21 16:32:38 +10:00 committed by Benjamin Herrenschmidt
parent 39a360ef72
commit 1739ea9e13
6 changed files with 29 additions and 35 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/powerpc/include/asm/paca.h
View File

@ -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
*/

1
arch/powerpc/kernel/asm-offsets.c
View File

@ -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));

9
arch/powerpc/kernel/entry_64.S
View File

@ -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

32
arch/powerpc/kernel/sysfs.c
View File

@ -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 (!current->thread.dscr_inherit) {
current->thread.dscr = dscr_default;
mtspr(SPRN_DSCR, dscr_default);
}
}
static ssize_t __used store_dscr_default(struct device *dev,
struct device_attribute *attr, const char *buf,
size_t count)
@ -532,7 +538,7 @@ static ssize_t __used store_dscr_default(struct device *dev,
return -EINVAL;
dscr_default = val;
on_each_cpu(update_dscr, NULL, 1);
on_each_cpu(write_dscr, &val, 1);
return count;
}

16
arch/powerpc/kernel/tm.S
View File

@ -78,12 +78,6 @@ _GLOBAL(tm_abort)
TABORT(R3)
blr
.section ".toc","aw"
DSCR_DEFAULT:
.tc dscr_default[TC],dscr_default
.section ".text"
/* void tm_reclaim(struct thread_struct *thread,
* unsigned long orig_msr,
* uint8_t cause)
@ -298,9 +292,8 @@ dont_backup_fp:
mtlr r0
ld r2, STK_GOT(r1)
/* Load system default DSCR */
ld r4, DSCR_DEFAULT@toc(r2)
ld r0, 0(r4)
/* Load CPU's default DSCR */
ld r0, PACA_DSCR(r13)
mtspr SPRN_DSCR, r0
blr
@ -479,9 +472,8 @@ restore_gprs:
mtlr r0
ld r2, STK_GOT(r1)
/* Load system default DSCR */
ld r4, DSCR_DEFAULT@toc(r2)
ld r0, 0(r4)
/* Load CPU's default DSCR */
ld r0, PACA_DSCR(r13)
mtspr SPRN_DSCR, r0
blr

3
arch/powerpc/kvm/book3s_hv_rmhandlers.S
View File

@ -286,8 +286,7 @@ kvm_start_guest:
beq kvm_no_guest
/* Set HSTATE_DSCR(r13) to something sensible */
LOAD_REG_ADDR(r6, dscr_default)
ld r6, 0(r6)
ld r6, PACA_DSCR(r13)
std r6, HSTATE_DSCR(r13)
bl kvmppc_hv_entry