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ARM: Optimize multi-CPU tlb flushing a little more
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The compiler does not conditionalize the assembly instructions for
the tlb operations, which leads to sub-optimal code being generated
when building a kernel for multiple CPUs.

We can tweak things fairly simply as the code fragment below shows:

    17f8:       e3120001        tst     r2, #1  ; 0x1
...
    1800:       0a000000        beq     1808 <handle_pte_fault+0x194>
    1804:       ee061f10        mcr     15, 0, r1, cr6, cr0, {0}
    1808:       e3120004        tst     r2, #4  ; 0x4
    180c:       0a000000        beq     1814 <handle_pte_fault+0x1a0>
    1810:       ee081f36        mcr     15, 0, r1, cr8, cr6, {1}
becomes:
    17f0:       e3120001        tst     r2, #1  ; 0x1
    17f4:       1e063f10        mcrne   15, 0, r3, cr6, cr0, {0}
    17f8:       e3120004        tst     r2, #4  ; 0x4
    17fc:       1e083f36        mcrne   15, 0, r3, cr8, cr6, {1}

Overall, for Realview with V6 and V7 CPUs configured:

   text    data     bss     dec     hex filename
4153998  207340 5371036 9732374  948116 ../build/realview/vmlinux.before
4153366  207332 5371036 9731734  947e96 ../build/realview/vmlinux.after

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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Russell King committed Mar 24, 2012
1 parent d9277d5 commit 87067a9
Showing 1 changed file with 58 additions and 78 deletions.
136 changes: 58 additions & 78 deletions arch/arm/include/asm/tlbflush.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -318,6 +318,21 @@ extern struct cpu_tlb_fns cpu_tlb;

#define tlb_flag(f) ((always_tlb_flags & (f)) || (__tlb_flag & possible_tlb_flags & (f)))

#define __tlb_op(f, insnarg, arg) \
do { \
if (always_tlb_flags & (f)) \
asm("mcr " insnarg \
: : "r" (arg) : "cc"); \
else if (possible_tlb_flags & (f)) \
asm("tst %1, %2\n\t" \
"mcrne " insnarg \
: : "r" (arg), "r" (__tlb_flag), "Ir" (f) \
: "cc"); \
} while (0)

#define tlb_op(f, regs, arg) __tlb_op(f, "p15, 0, %0, " regs, arg)
#define tlb_l2_op(f, regs, arg) __tlb_op(f, "p15, 1, %0, " regs, arg)

static inline void local_flush_tlb_all(void)
{
const int zero = 0;
Expand All @@ -326,16 +341,11 @@ static inline void local_flush_tlb_all(void)
if (tlb_flag(TLB_WB))
dsb();

if (tlb_flag(TLB_V3_FULL))
asm("mcr p15, 0, %0, c6, c0, 0" : : "r" (zero) : "cc");
if (tlb_flag(TLB_V4_U_FULL | TLB_V6_U_FULL))
asm("mcr p15, 0, %0, c8, c7, 0" : : "r" (zero) : "cc");
if (tlb_flag(TLB_V4_D_FULL | TLB_V6_D_FULL))
asm("mcr p15, 0, %0, c8, c6, 0" : : "r" (zero) : "cc");
if (tlb_flag(TLB_V4_I_FULL | TLB_V6_I_FULL))
asm("mcr p15, 0, %0, c8, c5, 0" : : "r" (zero) : "cc");
if (tlb_flag(TLB_V7_UIS_FULL))
asm("mcr p15, 0, %0, c8, c3, 0" : : "r" (zero) : "cc");
tlb_op(TLB_V3_FULL, "c6, c0, 0", zero);
tlb_op(TLB_V4_U_FULL | TLB_V6_U_FULL, "c8, c7, 0", zero);
tlb_op(TLB_V4_D_FULL | TLB_V6_D_FULL, "c8, c6, 0", zero);
tlb_op(TLB_V4_I_FULL | TLB_V6_I_FULL, "c8, c5, 0", zero);
tlb_op(TLB_V7_UIS_FULL, "c8, c3, 0", zero);

if (tlb_flag(TLB_BARRIER)) {
dsb();
Expand All @@ -352,29 +362,23 @@ static inline void local_flush_tlb_mm(struct mm_struct *mm)
if (tlb_flag(TLB_WB))
dsb();

if (cpumask_test_cpu(get_cpu(), mm_cpumask(mm))) {
if (tlb_flag(TLB_V3_FULL))
asm("mcr p15, 0, %0, c6, c0, 0" : : "r" (zero) : "cc");
if (tlb_flag(TLB_V4_U_FULL))
asm("mcr p15, 0, %0, c8, c7, 0" : : "r" (zero) : "cc");
if (tlb_flag(TLB_V4_D_FULL))
asm("mcr p15, 0, %0, c8, c6, 0" : : "r" (zero) : "cc");
if (tlb_flag(TLB_V4_I_FULL))
asm("mcr p15, 0, %0, c8, c5, 0" : : "r" (zero) : "cc");
if (possible_tlb_flags & (TLB_V3_FULL|TLB_V4_U_FULL|TLB_V4_D_FULL|TLB_V4_I_FULL)) {
if (cpumask_test_cpu(get_cpu(), mm_cpumask(mm))) {
tlb_op(TLB_V3_FULL, "c6, c0, 0", zero);
tlb_op(TLB_V4_U_FULL, "c8, c7, 0", zero);
tlb_op(TLB_V4_D_FULL, "c8, c6, 0", zero);
tlb_op(TLB_V4_I_FULL, "c8, c5, 0", zero);
}
put_cpu();
}
put_cpu();

if (tlb_flag(TLB_V6_U_ASID))
asm("mcr p15, 0, %0, c8, c7, 2" : : "r" (asid) : "cc");
if (tlb_flag(TLB_V6_D_ASID))
asm("mcr p15, 0, %0, c8, c6, 2" : : "r" (asid) : "cc");
if (tlb_flag(TLB_V6_I_ASID))
asm("mcr p15, 0, %0, c8, c5, 2" : : "r" (asid) : "cc");
if (tlb_flag(TLB_V7_UIS_ASID))

tlb_op(TLB_V6_U_ASID, "c8, c7, 2", asid);
tlb_op(TLB_V6_D_ASID, "c8, c6, 2", asid);
tlb_op(TLB_V6_I_ASID, "c8, c5, 2", asid);
#ifdef CONFIG_ARM_ERRATA_720789
asm("mcr p15, 0, %0, c8, c3, 0" : : "r" (zero) : "cc");
tlb_op(TLB_V7_UIS_ASID, "c8, c3, 0", zero);
#else
asm("mcr p15, 0, %0, c8, c3, 2" : : "r" (asid) : "cc");
tlb_op(TLB_V7_UIS_ASID, "c8, c3, 2", asid);
#endif

if (tlb_flag(TLB_BARRIER))
Expand All @@ -392,30 +396,23 @@ local_flush_tlb_page(struct vm_area_struct *vma, unsigned long uaddr)
if (tlb_flag(TLB_WB))
dsb();

if (cpumask_test_cpu(smp_processor_id(), mm_cpumask(vma->vm_mm))) {
if (tlb_flag(TLB_V3_PAGE))
asm("mcr p15, 0, %0, c6, c0, 0" : : "r" (uaddr) : "cc");
if (tlb_flag(TLB_V4_U_PAGE))
asm("mcr p15, 0, %0, c8, c7, 1" : : "r" (uaddr) : "cc");
if (tlb_flag(TLB_V4_D_PAGE))
asm("mcr p15, 0, %0, c8, c6, 1" : : "r" (uaddr) : "cc");
if (tlb_flag(TLB_V4_I_PAGE))
asm("mcr p15, 0, %0, c8, c5, 1" : : "r" (uaddr) : "cc");
if (possible_tlb_flags & (TLB_V3_PAGE|TLB_V4_U_PAGE|TLB_V4_D_PAGE|TLB_V4_I_PAGE|TLB_V4_I_FULL) &&
cpumask_test_cpu(smp_processor_id(), mm_cpumask(vma->vm_mm))) {
tlb_op(TLB_V3_PAGE, "c6, c0, 0", uaddr);
tlb_op(TLB_V4_U_PAGE, "c8, c7, 1", uaddr);
tlb_op(TLB_V4_D_PAGE, "c8, c6, 1", uaddr);
tlb_op(TLB_V4_I_PAGE, "c8, c5, 1", uaddr);
if (!tlb_flag(TLB_V4_I_PAGE) && tlb_flag(TLB_V4_I_FULL))
asm("mcr p15, 0, %0, c8, c5, 0" : : "r" (zero) : "cc");
}

if (tlb_flag(TLB_V6_U_PAGE))
asm("mcr p15, 0, %0, c8, c7, 1" : : "r" (uaddr) : "cc");
if (tlb_flag(TLB_V6_D_PAGE))
asm("mcr p15, 0, %0, c8, c6, 1" : : "r" (uaddr) : "cc");
if (tlb_flag(TLB_V6_I_PAGE))
asm("mcr p15, 0, %0, c8, c5, 1" : : "r" (uaddr) : "cc");
if (tlb_flag(TLB_V7_UIS_PAGE))
tlb_op(TLB_V6_U_PAGE, "c8, c7, 1", uaddr);
tlb_op(TLB_V6_D_PAGE, "c8, c6, 1", uaddr);
tlb_op(TLB_V6_I_PAGE, "c8, c5, 1", uaddr);
#ifdef CONFIG_ARM_ERRATA_720789
asm("mcr p15, 0, %0, c8, c3, 3" : : "r" (uaddr & PAGE_MASK) : "cc");
tlb_op(TLB_V7_UIS_PAGE, "c8, c3, 3", uaddr & PAGE_MASK);
#else
asm("mcr p15, 0, %0, c8, c3, 1" : : "r" (uaddr) : "cc");
tlb_op(TLB_V7_UIS_PAGE, "c8, c3, 1", uaddr);
#endif

if (tlb_flag(TLB_BARRIER))
Expand All @@ -432,25 +429,17 @@ static inline void local_flush_tlb_kernel_page(unsigned long kaddr)
if (tlb_flag(TLB_WB))
dsb();

if (tlb_flag(TLB_V3_PAGE))
asm("mcr p15, 0, %0, c6, c0, 0" : : "r" (kaddr) : "cc");
if (tlb_flag(TLB_V4_U_PAGE))
asm("mcr p15, 0, %0, c8, c7, 1" : : "r" (kaddr) : "cc");
if (tlb_flag(TLB_V4_D_PAGE))
asm("mcr p15, 0, %0, c8, c6, 1" : : "r" (kaddr) : "cc");
if (tlb_flag(TLB_V4_I_PAGE))
asm("mcr p15, 0, %0, c8, c5, 1" : : "r" (kaddr) : "cc");
tlb_op(TLB_V3_PAGE, "c6, c0, 0", kaddr);
tlb_op(TLB_V4_U_PAGE, "c8, c7, 1", kaddr);
tlb_op(TLB_V4_D_PAGE, "c8, c6, 1", kaddr);
tlb_op(TLB_V4_I_PAGE, "c8, c5, 1", kaddr);
if (!tlb_flag(TLB_V4_I_PAGE) && tlb_flag(TLB_V4_I_FULL))
asm("mcr p15, 0, %0, c8, c5, 0" : : "r" (zero) : "cc");

if (tlb_flag(TLB_V6_U_PAGE))
asm("mcr p15, 0, %0, c8, c7, 1" : : "r" (kaddr) : "cc");
if (tlb_flag(TLB_V6_D_PAGE))
asm("mcr p15, 0, %0, c8, c6, 1" : : "r" (kaddr) : "cc");
if (tlb_flag(TLB_V6_I_PAGE))
asm("mcr p15, 0, %0, c8, c5, 1" : : "r" (kaddr) : "cc");
if (tlb_flag(TLB_V7_UIS_PAGE))
asm("mcr p15, 0, %0, c8, c3, 1" : : "r" (kaddr) : "cc");
tlb_op(TLB_V6_U_PAGE, "c8, c7, 1", kaddr);
tlb_op(TLB_V6_D_PAGE, "c8, c6, 1", kaddr);
tlb_op(TLB_V6_I_PAGE, "c8, c5, 1", kaddr);
tlb_op(TLB_V7_UIS_PAGE, "c8, c3, 1", kaddr);

if (tlb_flag(TLB_BARRIER)) {
dsb();
Expand All @@ -475,13 +464,8 @@ static inline void flush_pmd_entry(void *pmd)
{
const unsigned int __tlb_flag = __cpu_tlb_flags;

if (tlb_flag(TLB_DCLEAN))
asm("mcr p15, 0, %0, c7, c10, 1 @ flush_pmd"
: : "r" (pmd) : "cc");

if (tlb_flag(TLB_L2CLEAN_FR))
asm("mcr p15, 1, %0, c15, c9, 1 @ L2 flush_pmd"
: : "r" (pmd) : "cc");
tlb_op(TLB_DCLEAN, "c7, c10, 1 @ flush_pmd", pmd);
tlb_l2_op(TLB_L2CLEAN_FR, "c15, c9, 1 @ L2 flush_pmd", pmd);

if (tlb_flag(TLB_WB))
dsb();
Expand All @@ -491,15 +475,11 @@ static inline void clean_pmd_entry(void *pmd)
{
const unsigned int __tlb_flag = __cpu_tlb_flags;

if (tlb_flag(TLB_DCLEAN))
asm("mcr p15, 0, %0, c7, c10, 1 @ flush_pmd"
: : "r" (pmd) : "cc");

if (tlb_flag(TLB_L2CLEAN_FR))
asm("mcr p15, 1, %0, c15, c9, 1 @ L2 flush_pmd"
: : "r" (pmd) : "cc");
tlb_op(TLB_DCLEAN, "c7, c10, 1 @ flush_pmd", pmd);
tlb_l2_op(TLB_L2CLEAN_FR, "c15, c9, 1 @ L2 flush_pmd", pmd);
}

#undef tlb_op
#undef tlb_flag
#undef always_tlb_flags
#undef possible_tlb_flags
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