arch/tile: use interrupt critical sections less

In general we want to avoid ever touching memory while within an
interrupt critical section, since the page fault path goes through
a different path from the hypervisor when in an interrupt critical
section, and we carefully decided with tilegx that we didn't need
to support this path in the kernel.  (On tilepro we did implement
that path as part of supporting atomic instructions in software.)

In practice we always need to touch the kernel stack, since that's
where we store the interrupt state before releasing the critical
section, but this change cleans up a few things.  The IRQ_ENABLE
macro is split up so that when we want to enable interrupts in a
deferred way (e.g. for cpu_idle or for interrupt return) we can
read the per-cpu enable mask before entering the critical section.
The cache-migration code is changed to use interrupt masking instead
of interrupt critical sections.  And, the interrupt-entry code is
changed so that we defer loading "tp" from per-cpu data until after
we have released the interrupt critical section.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

diff --git a/arch/tile/include/asm/irqflags.h b/arch/tile/include/asm/irqflags.h
index 5db0ce54284d6dbe39a0e1d103934df659615417..b4e96fef2cf8edc0b4931af8edcce502c7bebd4f 100644 (file)
--- a/arch/tile/include/asm/irqflags.h
+++ b/arch/tile/include/asm/irqflags.h
@@ -28,10 +28,10 @@
  */
 #if CHIP_HAS_AUX_PERF_COUNTERS()
 #define LINUX_MASKABLE_INTERRUPTS_HI \
-       (~(INT_MASK_HI(INT_PERF_COUNT) | INT_MASK_HI(INT_AUX_PERF_COUNT)))
+       (~(INT_MASK_HI(INT_PERF_COUNT) | INT_MASK_HI(INT_AUX_PERF_COUNT)))
 #else
 #define LINUX_MASKABLE_INTERRUPTS_HI \
-       (~(INT_MASK_HI(INT_PERF_COUNT)))
+       (~(INT_MASK_HI(INT_PERF_COUNT)))
 #endif
 
 #else
@@ -90,6 +90,14 @@
        __insn_mtspr(SPR_INTERRUPT_MASK_RESET_K_0, (unsigned long)(__m)); \
        __insn_mtspr(SPR_INTERRUPT_MASK_RESET_K_1, (unsigned long)(__m>>32)); \
 } while (0)
+#define interrupt_mask_save_mask() \
+       (__insn_mfspr(SPR_INTERRUPT_MASK_SET_K_0) | \
+        (((unsigned long long)__insn_mfspr(SPR_INTERRUPT_MASK_SET_K_1))<<32))
+#define interrupt_mask_restore_mask(mask) do { \
+       unsigned long long __m = (mask); \
+       __insn_mtspr(SPR_INTERRUPT_MASK_K_0, (unsigned long)(__m)); \
+       __insn_mtspr(SPR_INTERRUPT_MASK_K_1, (unsigned long)(__m>>32)); \
+} while (0)
 #else
 #define interrupt_mask_set(n) \
        __insn_mtspr(SPR_INTERRUPT_MASK_SET_K, (1UL << (n)))
@@ -101,6 +109,10 @@
        __insn_mtspr(SPR_INTERRUPT_MASK_SET_K, (mask))
 #define interrupt_mask_reset_mask(mask) \
        __insn_mtspr(SPR_INTERRUPT_MASK_RESET_K, (mask))
+#define interrupt_mask_save_mask() \
+       __insn_mfspr(SPR_INTERRUPT_MASK_K)
+#define interrupt_mask_restore_mask(mask) \
+       __insn_mtspr(SPR_INTERRUPT_MASK_K, (mask))
 #endif
 
 /*
@@ -122,7 +134,7 @@ DECLARE_PER_CPU(unsigned long long, interrupts_enabled_mask);
 
 /* Disable all interrupts, including NMIs. */
 #define arch_local_irq_disable_all() \
-       interrupt_mask_set_mask(-1UL)
+       interrupt_mask_set_mask(-1ULL)
 
 /* Re-enable all maskable interrupts. */
 #define arch_local_irq_enable() \
@@ -179,7 +191,7 @@ DECLARE_PER_CPU(unsigned long long, interrupts_enabled_mask);
 #ifdef __tilegx__
 
 #if INT_MEM_ERROR != 0
-# error Fix IRQ_DISABLED() macro
+# error Fix IRQS_DISABLED() macro
 #endif
 
 /* Return 0 or 1 to indicate whether interrupts are currently disabled. */
@@ -207,9 +219,10 @@ DECLARE_PER_CPU(unsigned long long, interrupts_enabled_mask);
        mtspr   SPR_INTERRUPT_MASK_SET_K, tmp
 
 /* Enable interrupts. */
-#define IRQ_ENABLE(tmp0, tmp1)                                 \
+#define IRQ_ENABLE_LOAD(tmp0, tmp1)                            \
        GET_INTERRUPTS_ENABLED_MASK_PTR(tmp0);                  \
-       ld      tmp0, tmp0;                                     \
+       ld      tmp0, tmp0
+#define IRQ_ENABLE_APPLY(tmp0, tmp1)                           \
        mtspr   SPR_INTERRUPT_MASK_RESET_K, tmp0
 
 #else /* !__tilegx__ */
@@ -253,17 +266,22 @@ DECLARE_PER_CPU(unsigned long long, interrupts_enabled_mask);
        mtspr   SPR_INTERRUPT_MASK_SET_K_1, tmp
 
 /* Enable interrupts. */
-#define IRQ_ENABLE(tmp0, tmp1)                                 \
+#define IRQ_ENABLE_LOAD(tmp0, tmp1)                            \
        GET_INTERRUPTS_ENABLED_MASK_PTR(tmp0);                  \
        {                                                       \
         lw     tmp0, tmp0;                                     \
         addi   tmp1, tmp0, 4                                   \
        };                                                      \
-       lw      tmp1, tmp1;                                     \
+       lw      tmp1, tmp1
+#define IRQ_ENABLE_APPLY(tmp0, tmp1)                           \
        mtspr   SPR_INTERRUPT_MASK_RESET_K_0, tmp0;             \
        mtspr   SPR_INTERRUPT_MASK_RESET_K_1, tmp1
 #endif
 
+#define IRQ_ENABLE(tmp0, tmp1)                                 \
+       IRQ_ENABLE_LOAD(tmp0, tmp1);                            \
+       IRQ_ENABLE_APPLY(tmp0, tmp1)
+
 /*
  * Do the CPU's IRQ-state tracing from assembly code. We call a
  * C function, but almost everywhere we do, we don't mind clobbering

diff --git a/arch/tile/kernel/entry.S b/arch/tile/kernel/entry.S
index 431e9ae60488c73f29c35761170150e7f65a7a92..f8d61558b5e40c9f838f2baf5e4509a39c3944c2 100644 (file)
--- a/arch/tile/kernel/entry.S
+++ b/arch/tile/kernel/entry.S
@@ -99,8 +99,9 @@ STD_ENTRY(smp_nap)
  */
 STD_ENTRY(_cpu_idle)
        movei r1, 1
+       IRQ_ENABLE_LOAD(r2, r3)
        mtspr INTERRUPT_CRITICAL_SECTION, r1
-       IRQ_ENABLE(r2, r3)             /* unmask, but still with ICS set */
+       IRQ_ENABLE_APPLY(r2, r3)       /* unmask, but still with ICS set */
        mtspr INTERRUPT_CRITICAL_SECTION, zero
        .global _cpu_idle_nap
 _cpu_idle_nap:

diff --git a/arch/tile/kernel/intvec_64.S b/arch/tile/kernel/intvec_64.S
index 79c93e10ba27b1a11c939e216233ec5956b6b11a..3c1f626dad876963a8a10e2a593917f64e267070 100644 (file)
--- a/arch/tile/kernel/intvec_64.S
+++ b/arch/tile/kernel/intvec_64.S
@@ -219,7 +219,9 @@ intvec_\vecname:
         * This routine saves just the first four registers, plus the
         * stack context so we can do proper backtracing right away,
         * and defers to handle_interrupt to save the rest.
-        * The backtracer needs pc, ex1, lr, sp, r52, and faultnum.
+        * The backtracer needs pc, ex1, lr, sp, r52, and faultnum,
+        * and needs sp set to its final location at the bottom of
+        * the stack frame.
         */
        addli   r0, r0, PTREGS_OFFSET_LR - (PTREGS_SIZE + KSTK_PTREGS_GAP)
        wh64    r0   /* cache line 7 */
@@ -449,23 +451,6 @@ intvec_\vecname:
        push_reg r5, r52
        st      r52, r4
 
-       /* Load tp with our per-cpu offset. */
-#ifdef CONFIG_SMP
-       {
-        mfspr  r20, SPR_SYSTEM_SAVE_K_0
-        moveli r21, hw2_last(__per_cpu_offset)
-       }
-       {
-        shl16insli r21, r21, hw1(__per_cpu_offset)
-        bfextu r20, r20, 0, LOG2_THREAD_SIZE-1
-       }
-       shl16insli r21, r21, hw0(__per_cpu_offset)
-       shl3add r20, r20, r21
-       ld      tp, r20
-#else
-       move    tp, zero
-#endif
-
        /*
         * If we will be returning to the kernel, we will need to
         * reset the interrupt masks to the state they had before.
@@ -488,6 +473,44 @@ intvec_\vecname:
        .endif
        st      r21, r32
 
+       /*
+        * we've captured enough state to the stack (including in
+        * particular our EX_CONTEXT state) that we can now release
+        * the interrupt critical section and replace it with our
+        * standard "interrupts disabled" mask value.  This allows
+        * synchronous interrupts (and profile interrupts) to punch
+        * through from this point onwards.
+        *
+        * It's important that no code before this point touch memory
+        * other than our own stack (to keep the invariant that this
+        * is all that gets touched under ICS), and that no code after
+        * this point reference any interrupt-specific SPR, in particular
+        * the EX_CONTEXT_K_ values.
+        */
+       .ifc \function,handle_nmi
+       IRQ_DISABLE_ALL(r20)
+       .else
+       IRQ_DISABLE(r20, r21)
+       .endif
+       mtspr   INTERRUPT_CRITICAL_SECTION, zero
+
+       /* Load tp with our per-cpu offset. */
+#ifdef CONFIG_SMP
+       {
+        mfspr  r20, SPR_SYSTEM_SAVE_K_0
+        moveli r21, hw2_last(__per_cpu_offset)
+       }
+       {
+        shl16insli r21, r21, hw1(__per_cpu_offset)
+        bfextu r20, r20, 0, LOG2_THREAD_SIZE-1
+       }
+       shl16insli r21, r21, hw0(__per_cpu_offset)
+       shl3add r20, r20, r21
+       ld      tp, r20
+#else
+       move    tp, zero
+#endif
+
 #ifdef __COLLECT_LINKER_FEEDBACK__
        /*
         * Notify the feedback routines that we were in the
@@ -511,21 +534,6 @@ intvec_\vecname:
        FEEDBACK_ENTER(\function)
 #endif
 
-       /*
-        * we've captured enough state to the stack (including in
-        * particular our EX_CONTEXT state) that we can now release
-        * the interrupt critical section and replace it with our
-        * standard "interrupts disabled" mask value.  This allows
-        * synchronous interrupts (and profile interrupts) to punch
-        * through from this point onwards.
-        */
-       .ifc \function,handle_nmi
-       IRQ_DISABLE_ALL(r20)
-       .else
-       IRQ_DISABLE(r20, r21)
-       .endif
-       mtspr   INTERRUPT_CRITICAL_SECTION, zero
-
        /*
         * Prepare the first 256 stack bytes to be rapidly accessible
         * without having to fetch the background data.
@@ -718,9 +726,10 @@ STD_ENTRY(interrupt_return)
        beqzt   r30, .Lrestore_regs
        j       3f
 2:     TRACE_IRQS_ON
+       IRQ_ENABLE_LOAD(r20, r21)
        movei   r0, 1
        mtspr   INTERRUPT_CRITICAL_SECTION, r0
-       IRQ_ENABLE(r20, r21)
+       IRQ_ENABLE_APPLY(r20, r21)
        beqzt   r30, .Lrestore_regs
 3:
 
@@ -737,7 +746,6 @@ STD_ENTRY(interrupt_return)
         * that will save some cycles if this turns out to be a syscall.
         */
 .Lrestore_regs:
-       FEEDBACK_REENTER(interrupt_return)   /* called from elsewhere */
 
        /*
         * Rotate so we have one high bit and one low bit to test.

diff --git a/arch/tile/mm/init.c b/arch/tile/mm/init.c
index 7309988c9794c82f195572afd2b63658a4431cb4..51c5e517869a7e76448498a06f946989355c71a3 100644 (file)
--- a/arch/tile/mm/init.c
+++ b/arch/tile/mm/init.c
@@ -450,6 +450,7 @@ static pgd_t pgtables[PTRS_PER_PGD]
  */
 static void __init kernel_physical_mapping_init(pgd_t *pgd_base)
 {
+       unsigned long long irqmask;
        unsigned long address, pfn;
        pmd_t *pmd;
        pte_t *pte;
@@ -630,10 +631,13 @@ static void __init kernel_physical_mapping_init(pgd_t *pgd_base)
         *  - install pgtables[] as the real page table
         *  - flush the TLB so the new page table takes effect
         */
+       irqmask = interrupt_mask_save_mask();
+       interrupt_mask_set_mask(-1ULL);
        rc = flush_and_install_context(__pa(pgtables),
                                       init_pgprot((unsigned long)pgtables),
                                       __get_cpu_var(current_asid),
                                       cpumask_bits(my_cpu_mask));
+       interrupt_mask_restore_mask(irqmask);
        BUG_ON(rc != 0);
 
        /* Copy the page table back to the normal swapper_pg_dir. */

diff --git a/arch/tile/mm/migrate.h b/arch/tile/mm/migrate.h
index cd45a0837fa69cf7d57ced0dbb8985f875698929..91683d97917e6f79e07ddf291fd56b8559d25c93 100644 (file)
--- a/arch/tile/mm/migrate.h
+++ b/arch/tile/mm/migrate.h
@@ -24,6 +24,9 @@
 /*
  * This function is used as a helper when setting up the initial
  * page table (swapper_pg_dir).
+ *
+ * You must mask ALL interrupts prior to invoking this code, since
+ * you can't legally touch the stack during the cache flush.
  */
 extern int flush_and_install_context(HV_PhysAddr page_table, HV_PTE access,
                                     HV_ASID asid,
@@ -39,6 +42,9 @@ extern int flush_and_install_context(HV_PhysAddr page_table, HV_PTE access,
  *
  * Note that any non-NULL pointers must not point to the page that
  * is handled by the stack_pte itself.
+ *
+ * You must mask ALL interrupts prior to invoking this code, since
+ * you can't legally touch the stack during the cache flush.
  */
 extern int homecache_migrate_stack_and_flush(pte_t stack_pte, unsigned long va,
                                     size_t length, pte_t *stack_ptep,

diff --git a/arch/tile/mm/migrate_32.S b/arch/tile/mm/migrate_32.S
index ac01a7cdf77f243e5d6944fc7ae1795090ce9056..5305814bf187f52aa89f6b84e5f886cf273f5814 100644 (file)
--- a/arch/tile/mm/migrate_32.S
+++ b/arch/tile/mm/migrate_32.S
@@ -40,8 +40,7 @@
 #define FRAME_R32      16
 #define FRAME_R33      20
 #define FRAME_R34      24
-#define FRAME_R35      28
-#define FRAME_SIZE     32
+#define FRAME_SIZE     28
 
 
 
@@ -66,12 +65,11 @@
 #define r_my_cpumask   r5
 
 /* Locals (callee-save); must not be more than FRAME_xxx above. */
-#define r_save_ics     r30
-#define r_context_lo   r31
-#define r_context_hi   r32
-#define r_access_lo    r33
-#define r_access_hi    r34
-#define r_asid         r35
+#define r_context_lo   r30
+#define r_context_hi   r31
+#define r_access_lo    r32
+#define r_access_hi    r33
+#define r_asid         r34
 
 STD_ENTRY(flush_and_install_context)
        /*
@@ -104,11 +102,7 @@ STD_ENTRY(flush_and_install_context)
         sw r_tmp, r33
         addi r_tmp, sp, FRAME_R34
        }
-       {
-        sw r_tmp, r34
-        addi r_tmp, sp, FRAME_R35
-       }
-       sw r_tmp, r35
+       sw r_tmp, r34
 
        /* Move some arguments to callee-save registers. */
        {
@@ -121,13 +115,6 @@ STD_ENTRY(flush_and_install_context)
        }
        move r_asid, r_asid_in
 
-       /* Disable interrupts, since we can't use our stack. */
-       {
-        mfspr r_save_ics, INTERRUPT_CRITICAL_SECTION
-        movei r_tmp, 1
-       }
-       mtspr INTERRUPT_CRITICAL_SECTION, r_tmp
-
        /* First, flush our L2 cache. */
        {
         move r0, zero  /* cache_pa */
@@ -163,7 +150,7 @@ STD_ENTRY(flush_and_install_context)
        }
        {
         move r4, r_asid
-        movei r5, HV_CTX_DIRECTIO
+        moveli r5, HV_CTX_DIRECTIO | CTX_PAGE_FLAG
        }
        jal hv_install_context
        bnz r0, .Ldone
@@ -175,9 +162,6 @@ STD_ENTRY(flush_and_install_context)
        }
 
 .Ldone:
-       /* Reset interrupts back how they were before. */
-       mtspr INTERRUPT_CRITICAL_SECTION, r_save_ics
-
        /* Restore the callee-saved registers and return. */
        addli lr, sp, FRAME_SIZE
        {
@@ -202,10 +186,6 @@ STD_ENTRY(flush_and_install_context)
        }
        {
         lw r34, r_tmp
-        addli r_tmp, sp, FRAME_R35
-       }
-       {
-        lw r35, r_tmp
         addi sp, sp, FRAME_SIZE
        }
        jrp lr

diff --git a/arch/tile/mm/migrate_64.S b/arch/tile/mm/migrate_64.S
index e76fea688bebf83cc172c4ba5770bd2e299edfb7..1d15b10833d113ee077f8ea032503819ea4c257e 100644 (file)
--- a/arch/tile/mm/migrate_64.S
+++ b/arch/tile/mm/migrate_64.S
@@ -38,8 +38,7 @@
 #define FRAME_R30      16
 #define FRAME_R31      24
 #define FRAME_R32      32
-#define FRAME_R33      40
-#define FRAME_SIZE     48
+#define FRAME_SIZE     40
 
 
 
@@ -60,10 +59,9 @@
 #define r_my_cpumask   r3
 
 /* Locals (callee-save); must not be more than FRAME_xxx above. */
-#define r_save_ics     r30
-#define r_context      r31
-#define r_access       r32
-#define r_asid         r33
+#define r_context      r30
+#define r_access       r31
+#define r_asid         r32
 
 /*
  * Caller-save locals and frame constants are the same as
@@ -93,11 +91,7 @@ STD_ENTRY(flush_and_install_context)
         st r_tmp, r31
         addi r_tmp, sp, FRAME_R32
        }
-       {
-        st r_tmp, r32
-        addi r_tmp, sp, FRAME_R33
-       }
-       st r_tmp, r33
+       st r_tmp, r32
 
        /* Move some arguments to callee-save registers. */
        {
@@ -106,13 +100,6 @@ STD_ENTRY(flush_and_install_context)
        }
        move r_asid, r_asid_in
 
-       /* Disable interrupts, since we can't use our stack. */
-       {
-        mfspr r_save_ics, INTERRUPT_CRITICAL_SECTION
-        movei r_tmp, 1
-       }
-       mtspr INTERRUPT_CRITICAL_SECTION, r_tmp
-
        /* First, flush our L2 cache. */
        {
         move r0, zero  /* cache_pa */
@@ -147,7 +134,7 @@ STD_ENTRY(flush_and_install_context)
        }
        {
         move r2, r_asid
-        movei r3, HV_CTX_DIRECTIO
+        moveli r3, HV_CTX_DIRECTIO | CTX_PAGE_FLAG
        }
        jal hv_install_context
        bnez r0, 1f
@@ -158,10 +145,7 @@ STD_ENTRY(flush_and_install_context)
         jal hv_flush_all
        }
 
-1:      /* Reset interrupts back how they were before. */
-       mtspr INTERRUPT_CRITICAL_SECTION, r_save_ics
-
-       /* Restore the callee-saved registers and return. */
+1:     /* Restore the callee-saved registers and return. */
        addli lr, sp, FRAME_SIZE
        {
         ld lr, lr
@@ -177,10 +161,6 @@ STD_ENTRY(flush_and_install_context)
        }
        {
         ld r32, r_tmp
-        addli r_tmp, sp, FRAME_R33
-       }
-       {
-        ld r33, r_tmp
         addi sp, sp, FRAME_SIZE
        }
        jrp lr