[RFC PATCH 3/5] powerpc/mm/hash: Move kernel context to the starting of context range
Aneesh Kumar K.V
aneesh.kumar at linux.vnet.ibm.com
Tue Feb 7 14:48:51 AEDT 2017
This enables us to limit the max context based on platforms.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
---
arch/powerpc/include/asm/book3s/64/mmu-hash.h | 39 ++++++-------
arch/powerpc/include/asm/mmu_context.h | 2 -
arch/powerpc/kvm/book3s_64_mmu_host.c | 2 +-
arch/powerpc/mm/hash_utils_64.c | 5 --
arch/powerpc/mm/mmu_context_book3s64.c | 79 +++++++++++++++++----------
arch/powerpc/mm/slb_low.S | 20 ++-----
6 files changed, 73 insertions(+), 74 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/64/mmu-hash.h b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
index 0735d5a8049f..014a9bb197cd 100644
--- a/arch/powerpc/include/asm/book3s/64/mmu-hash.h
+++ b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
@@ -493,10 +493,10 @@ extern void slb_set_size(u16 size);
* For user processes max context id is limited to ((1ul << 19) - 5)
* for kernel space, we use the top 4 context ids to map address as below
* NOTE: each context only support 64TB now.
- * 0x7fffc - [ 0xc000000000000000 - 0xc0003fffffffffff ]
- * 0x7fffd - [ 0xd000000000000000 - 0xd0003fffffffffff ]
- * 0x7fffe - [ 0xe000000000000000 - 0xe0003fffffffffff ]
- * 0x7ffff - [ 0xf000000000000000 - 0xf0003fffffffffff ]
+ * 0x00000 - [ 0xc000000000000000 - 0xc0003fffffffffff ]
+ * 0x00001 - [ 0xd000000000000000 - 0xd0003fffffffffff ]
+ * 0x00002 - [ 0xe000000000000000 - 0xe0003fffffffffff ]
+ * 0x00003 - [ 0xf000000000000000 - 0xf0003fffffffffff ]
*
* The proto-VSIDs are then scrambled into real VSIDs with the
* multiplicative hash:
@@ -510,15 +510,9 @@ extern void slb_set_size(u16 size);
* robust scattering in the hash table (at least based on some initial
* results).
*
- * We also consider VSID 0 special. We use VSID 0 for slb entries mapping
- * bad address. This enables us to consolidate bad address handling in
- * hash_page.
- *
* We also need to avoid the last segment of the last context, because that
* would give a protovsid of 0x1fffffffff. That will result in a VSID 0
- * because of the modulo operation in vsid scramble. But the vmemmap
- * (which is what uses region 0xf) will never be close to 64TB in size
- * (it's 56 bytes per page of system memory).
+ * because of the modulo operation in vsid scramble.
*/
#define CONTEXT_BITS 19
@@ -530,12 +524,15 @@ extern void slb_set_size(u16 size);
/*
* 256MB segment
* The proto-VSID space has 2^(CONTEX_BITS + ESID_BITS) - 1 segments
- * available for user + kernel mapping. The top 4 contexts are used for
+ * available for user + kernel mapping. The bottom 4 contexts are used for
* kernel mapping. Each segment contains 2^28 bytes. Each
- * context maps 2^46 bytes (64TB) so we can support 2^19-1 contexts
- * (19 == 37 + 28 - 46).
+ * context maps 2^46 bytes (64TB).
+ *
+ * We also need to avoid the last segment of the last context, because that
+ * would give a protovsid of 0x1fffffffff. That will result in a VSID 0
+ * because of the modulo operation in vsid scramble.
*/
-#define MAX_USER_CONTEXT ((ASM_CONST(1) << CONTEXT_BITS) - 5)
+#define MAX_USER_CONTEXT ((ASM_CONST(1) << CONTEXT_BITS) - 2)
/*
* This should be computed such that protovosid * vsid_mulitplier
@@ -671,19 +668,19 @@ static inline unsigned long get_vsid(unsigned long context, unsigned long ea,
* This is only valid for addresses >= PAGE_OFFSET
*
* For kernel space, we use the top 4 context ids to map address as below
- * 0x7fffc - [ 0xc000000000000000 - 0xc0003fffffffffff ]
- * 0x7fffd - [ 0xd000000000000000 - 0xd0003fffffffffff ]
- * 0x7fffe - [ 0xe000000000000000 - 0xe0003fffffffffff ]
- * 0x7ffff - [ 0xf000000000000000 - 0xf0003fffffffffff ]
+ * 0x00000 - [ 0xc000000000000000 - 0xc0003fffffffffff ]
+ * 0x00001 - [ 0xd000000000000000 - 0xd0003fffffffffff ]
+ * 0x00002 - [ 0xe000000000000000 - 0xe0003fffffffffff ]
+ * 0x00003 - [ 0xf000000000000000 - 0xf0003fffffffffff ]
*/
static inline unsigned long get_kernel_vsid(unsigned long ea, int ssize)
{
unsigned long context;
/*
- * kernel take the top 4 context from the available range
+ * kernel take the first 4 context from the available range
*/
- context = (MAX_USER_CONTEXT) + ((ea >> 60) - 0xc) + 1;
+ context = (ea >> 60) - 0xc;
return get_vsid(context, ea, ssize);
}
diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index b9e3f0aca261..e6f6d2956227 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -51,13 +51,11 @@ static inline void switch_mmu_context(struct mm_struct *prev,
return switch_slb(tsk, next);
}
-extern int __init_new_context(void);
extern void __destroy_context(int context_id);
static inline void mmu_context_init(void) { }
#else
extern void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next,
struct task_struct *tsk);
-extern unsigned long __init_new_context(void);
extern void __destroy_context(unsigned long context_id);
extern void mmu_context_init(void);
#endif
diff --git a/arch/powerpc/kvm/book3s_64_mmu_host.c b/arch/powerpc/kvm/book3s_64_mmu_host.c
index a587e8f4fd26..fddb0e7dc7b8 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_host.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_host.c
@@ -390,7 +390,7 @@ int kvmppc_mmu_init(struct kvm_vcpu *vcpu)
struct kvmppc_vcpu_book3s *vcpu3s = to_book3s(vcpu);
int err;
- err = __init_new_context();
+ err = hash__init_new_context();
if (err < 0)
return -1;
vcpu3s->context_id[0] = err;
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index 67e19a0821be..978314b6b8d7 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -255,11 +255,6 @@ int htab_bolt_mapping(unsigned long vstart, unsigned long vend,
unsigned long vpn = hpt_vpn(vaddr, vsid, ssize);
unsigned long tprot = prot;
- /*
- * If we hit a bad address return error.
- */
- if (!vsid)
- return -1;
/* Make kernel text executable */
if (overlaps_kernel_text(vaddr, vaddr + step))
tprot &= ~HPTE_R_N;
diff --git a/arch/powerpc/mm/mmu_context_book3s64.c b/arch/powerpc/mm/mmu_context_book3s64.c
index 73bf6e14c3aa..fa3237b8e00f 100644
--- a/arch/powerpc/mm/mmu_context_book3s64.c
+++ b/arch/powerpc/mm/mmu_context_book3s64.c
@@ -30,17 +30,19 @@
static DEFINE_SPINLOCK(mmu_context_lock);
static DEFINE_IDA(mmu_context_ida);
-int __init_new_context(void)
+static int hash__init_new_context(struct mm_struct *mm)
{
- int index;
- int err;
+ int index, err;
again:
if (!ida_pre_get(&mmu_context_ida, GFP_KERNEL))
return -ENOMEM;
spin_lock(&mmu_context_lock);
- err = ida_get_new_above(&mmu_context_ida, 1, &index);
+ /*
+ * 0 - 3 context is taken by kernel.
+ */
+ err = ida_get_new_above(&mmu_context_ida, 4, &index);
spin_unlock(&mmu_context_lock);
if (err == -EAGAIN)
@@ -54,51 +56,68 @@ int __init_new_context(void)
spin_unlock(&mmu_context_lock);
return -ENOMEM;
}
-
+ /* The old code would re-promote on fork, we don't do that
+ * when using slices as it could cause problem promoting slices
+ * that have been forced down to 4K
+ *
+ * For book3s we have MMU_NO_CONTEXT set to be ~0. Hence check
+ * explicitly against context.id == 0. This ensures that we
+ * properly initialize context slice details for newly allocated
+ * mm's (which will have id == 0) and don't alter context slice
+ * inherited via fork (which will have id != 0).
+ *
+ * We should not be calling init_new_context() on init_mm. Hence a
+ * check against 0 is ok.
+ */
+ if (mm->context.id == 0)
+ slice_set_user_psize(mm, mmu_virtual_psize);
+ subpage_prot_init_new_context(mm);
return index;
}
-EXPORT_SYMBOL_GPL(__init_new_context);
-static int radix__init_new_context(struct mm_struct *mm, int index)
+
+static int radix__init_new_context(struct mm_struct *mm)
{
+ int index, err;
unsigned long rts_field;
+again:
+ if (!ida_pre_get(&mmu_context_ida, GFP_KERNEL))
+ return -ENOMEM;
+
+ spin_lock(&mmu_context_lock);
+ err = ida_get_new_above(&mmu_context_ida, 1, &index);
+ spin_unlock(&mmu_context_lock);
+
+ if (err == -EAGAIN)
+ goto again;
+ else if (err)
+ return err;
+
+ if (index > ((1UL << PRTB_SIZE_SHIFT) - 1)) {
+ spin_lock(&mmu_context_lock);
+ ida_remove(&mmu_context_ida, index);
+ spin_unlock(&mmu_context_lock);
+ return -ENOMEM;
+ }
/*
* set the process table entry,
*/
rts_field = radix__get_tree_size();
process_tb[index].prtb0 = cpu_to_be64(rts_field | __pa(mm->pgd) | RADIX_PGD_INDEX_SIZE);
- return 0;
+ return index;
}
int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
{
int index;
- index = __init_new_context();
+ if (radix_enabled())
+ index = radix__init_new_context(mm);
+ else
+ index = hash__init_new_context(mm);
if (index < 0)
return index;
- if (radix_enabled()) {
- radix__init_new_context(mm, index);
- } else {
-
- /* The old code would re-promote on fork, we don't do that
- * when using slices as it could cause problem promoting slices
- * that have been forced down to 4K
- *
- * For book3s we have MMU_NO_CONTEXT set to be ~0. Hence check
- * explicitly against context.id == 0. This ensures that we
- * properly initialize context slice details for newly allocated
- * mm's (which will have id == 0) and don't alter context slice
- * inherited via fork (which will have id != 0).
- *
- * We should not be calling init_new_context() on init_mm. Hence a
- * check against 0 is ok.
- */
- if (mm->context.id == 0)
- slice_set_user_psize(mm, mmu_virtual_psize);
- subpage_prot_init_new_context(mm);
- }
mm->context.id = index;
#ifdef CONFIG_PPC_ICSWX
mm->context.cop_lockp = kmalloc(sizeof(spinlock_t), GFP_KERNEL);
diff --git a/arch/powerpc/mm/slb_low.S b/arch/powerpc/mm/slb_low.S
index e2974fcd20f1..4ce050ea4200 100644
--- a/arch/powerpc/mm/slb_low.S
+++ b/arch/powerpc/mm/slb_low.S
@@ -45,13 +45,6 @@ _GLOBAL(slb_allocate_realmode)
/* r3 = address, r10 = esid, cr7 = <> PAGE_OFFSET */
blt cr7,0f /* user or kernel? */
- /* kernel address: proto-VSID = ESID */
- /* WARNING - MAGIC: we don't use the VSID 0xfffffffff, but
- * this code will generate the protoVSID 0xfffffffff for the
- * top segment. That's ok, the scramble below will translate
- * it to VSID 0, which is reserved as a bad VSID - one which
- * will never have any pages in it. */
-
/* Check if hitting the linear mapping or some other kernel space
*/
bne cr7,1f
@@ -63,12 +56,10 @@ _GLOBAL(slb_allocate_realmode)
slb_miss_kernel_load_linear:
li r11,0
/*
- * context = (MAX_USER_CONTEXT) + ((ea >> 60) - 0xc) + 1
+ * context = (ea >> 60) - 0xc
* r9 = region id.
*/
- addis r9,r9,(MAX_USER_CONTEXT - 0xc + 1)@ha
- addi r9,r9,(MAX_USER_CONTEXT - 0xc + 1)@l
-
+ subi r9,r9,0xc
BEGIN_FTR_SECTION
b slb_finish_load
@@ -77,9 +68,9 @@ END_MMU_FTR_SECTION_IFCLR(MMU_FTR_1T_SEGMENT)
1:
#ifdef CONFIG_SPARSEMEM_VMEMMAP
- /* Check virtual memmap region. To be patches at kernel boot */
cmpldi cr0,r9,0xf
bne 1f
+/* Check virtual memmap region. To be patched at kernel boot */
.globl slb_miss_kernel_load_vmemmap
slb_miss_kernel_load_vmemmap:
li r11,0
@@ -102,11 +93,10 @@ slb_miss_kernel_load_io:
li r11,0
6:
/*
- * context = (MAX_USER_CONTEXT) + ((ea >> 60) - 0xc) + 1
+ * context = (ea >> 60) - 0xc
* r9 = region id.
*/
- addis r9,r9,(MAX_USER_CONTEXT - 0xc + 1)@ha
- addi r9,r9,(MAX_USER_CONTEXT - 0xc + 1)@l
+ subi r9,r9,0xc
BEGIN_FTR_SECTION
b slb_finish_load
--
2.7.4
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