powerpc: Per process DSCR + some fixes (try#4)
The DSCR (aka Data Stream Control Register) is supported on some
server PowerPC chips and allow some control over the prefetch
of data streams.
This patch allows the value to be specified per thread by emulating
the corresponding mfspr and mtspr instructions. Children of such
threads inherit the value. Other threads use a default value that
can be specified in sysfs - /sys/devices/system/cpu/dscr_default.
If a thread starts with non default value in the sysfs entry,
all children threads inherit this non default value even if
the sysfs value is changed later.
Signed-off-by: Alexey Kardashevskiy <aik@au1.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 23e6a93..6887661 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -74,6 +74,7 @@
DEFINE(AUDITCONTEXT, offsetof(struct task_struct, audit_context));
DEFINE(SIGSEGV, SIGSEGV);
DEFINE(NMI_MASK, NMI_MASK);
+ DEFINE(THREAD_DSCR, offsetof(struct thread_struct, dscr));
#else
DEFINE(THREAD_INFO, offsetof(struct task_struct, stack));
#endif /* CONFIG_PPC64 */
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index dbf5bfa..6469370 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -421,6 +421,12 @@
std r24,THREAD_VRSAVE(r3)
END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
#endif /* CONFIG_ALTIVEC */
+#ifdef CONFIG_PPC64
+BEGIN_FTR_SECTION
+ mfspr r25,SPRN_DSCR
+ std r25,THREAD_DSCR(r3)
+END_FTR_SECTION_IFSET(CPU_FTR_DSCR)
+#endif
and. r0,r0,r22
beq+ 1f
andc r22,r22,r0
@@ -522,6 +528,15 @@
mtspr SPRN_VRSAVE,r0 /* if G4, restore VRSAVE reg */
END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
#endif /* CONFIG_ALTIVEC */
+#ifdef CONFIG_PPC64
+BEGIN_FTR_SECTION
+ ld r0,THREAD_DSCR(r4)
+ cmpd r0,r25
+ beq 1f
+ mtspr SPRN_DSCR,r0
+1:
+END_FTR_SECTION_IFSET(CPU_FTR_DSCR)
+#endif
/* r3-r13 are destroyed -- Cort */
REST_8GPRS(14, r1)
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index f74f355..a01c2d9 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -702,6 +702,8 @@
/*
* Copy a thread..
*/
+extern unsigned long dscr_default; /* defined in arch/powerpc/kernel/sysfs.c */
+
int copy_thread(unsigned long clone_flags, unsigned long usp,
unsigned long unused, struct task_struct *p,
struct pt_regs *regs)
@@ -769,6 +771,20 @@
p->thread.ksp_vsid = sp_vsid;
}
#endif /* CONFIG_PPC_STD_MMU_64 */
+#ifdef CONFIG_PPC64
+ if (cpu_has_feature(CPU_FTR_DSCR)) {
+ if (current->thread.dscr_inherit) {
+ p->thread.dscr_inherit = 1;
+ p->thread.dscr = current->thread.dscr;
+ } else if (0 != dscr_default) {
+ p->thread.dscr_inherit = 1;
+ p->thread.dscr = dscr_default;
+ } else {
+ p->thread.dscr_inherit = 0;
+ p->thread.dscr = 0;
+ }
+ }
+#endif
/*
* The PPC64 ABI makes use of a TOC to contain function
diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
index c0d8c20..f0f2199 100644
--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c
@@ -182,6 +182,41 @@
static SYSDEV_ATTR(spurr, 0600, show_spurr, NULL);
static SYSDEV_ATTR(dscr, 0600, show_dscr, store_dscr);
static SYSDEV_ATTR(purr, 0600, show_purr, store_purr);
+
+unsigned long dscr_default = 0;
+EXPORT_SYMBOL(dscr_default);
+
+static ssize_t show_dscr_default(struct sysdev_class *class,
+ struct sysdev_class_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%lx\n", dscr_default);
+}
+
+static ssize_t __used store_dscr_default(struct sysdev_class *class,
+ struct sysdev_class_attribute *attr, const char *buf,
+ size_t count)
+{
+ unsigned long val;
+ int ret = 0;
+
+ ret = sscanf(buf, "%lx", &val);
+ if (ret != 1)
+ return -EINVAL;
+ dscr_default = val;
+
+ return count;
+}
+
+static SYSDEV_CLASS_ATTR(dscr_default, 0600,
+ show_dscr_default, store_dscr_default);
+
+static void sysfs_create_dscr_default(void)
+{
+ int err = 0;
+ if (cpu_has_feature(CPU_FTR_DSCR))
+ err = sysfs_create_file(&cpu_sysdev_class.kset.kobj,
+ &attr_dscr_default.attr);
+}
#endif /* CONFIG_PPC64 */
#ifdef HAS_PPC_PMC_PA6T
@@ -617,6 +652,9 @@
if (cpu_online(cpu))
register_cpu_online(cpu);
}
+#ifdef CONFIG_PPC64
+ sysfs_create_dscr_default();
+#endif /* CONFIG_PPC64 */
return 0;
}
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 5ddb801..cb71cf2 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -909,6 +909,26 @@
return emulate_isel(regs, instword);
}
+#ifdef CONFIG_PPC64
+ /* Emulate the mfspr rD, DSCR. */
+ if (((instword & PPC_INST_MFSPR_DSCR_MASK) == PPC_INST_MFSPR_DSCR) &&
+ cpu_has_feature(CPU_FTR_DSCR)) {
+ PPC_WARN_EMULATED(mfdscr, regs);
+ rd = (instword >> 21) & 0x1f;
+ regs->gpr[rd] = mfspr(SPRN_DSCR);
+ return 0;
+ }
+ /* Emulate the mtspr DSCR, rD. */
+ if (((instword & PPC_INST_MTSPR_DSCR_MASK) == PPC_INST_MTSPR_DSCR) &&
+ cpu_has_feature(CPU_FTR_DSCR)) {
+ PPC_WARN_EMULATED(mtdscr, regs);
+ rd = (instword >> 21) & 0x1f;
+ mtspr(SPRN_DSCR, regs->gpr[rd]);
+ current->thread.dscr_inherit = 1;
+ return 0;
+ }
+#endif
+
return -EINVAL;
}
@@ -1506,6 +1526,10 @@
#ifdef CONFIG_VSX
WARN_EMULATED_SETUP(vsx),
#endif
+#ifdef CONFIG_PPC64
+ WARN_EMULATED_SETUP(mfdscr),
+ WARN_EMULATED_SETUP(mtdscr),
+#endif
};
u32 ppc_warn_emulated;