diff options
| author | Michael Ellerman <mpe@ellerman.id.au> | 2018-07-24 01:07:54 +1000 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2018-08-08 00:32:26 +1000 |
| commit | ee13cb249fabdff8b90aaff61add347749280087 (patch) | |
| tree | 6b37d585ba08ac9349db5392bc2ceff65dce1c39 /arch/powerpc/kernel/entry_64.S | |
| parent | dc8c6cce9a26a51fc19961accb978217a3ba8c75 (diff) | |
powerpc/64s: Add support for software count cache flush
Some CPU revisions support a mode where the count cache needs to be
flushed by software on context switch. Additionally some revisions may
have a hardware accelerated flush, in which case the software flush
sequence can be shortened.
If we detect the appropriate flag from firmware we patch a branch
into _switch() which takes us to a count cache flush sequence.
That sequence in turn may be patched to return early if we detect that
the CPU supports accelerating the flush sequence in hardware.
Add debugfs support for reporting the state of the flush, as well as
runtime disabling it.
And modify the spectre_v2 sysfs file to report the state of the
software flush.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/kernel/entry_64.S')
| -rw-r--r-- | arch/powerpc/kernel/entry_64.S | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index a9e74ecdab0b..2206912ea4f0 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -25,6 +25,7 @@ #include <asm/page.h> #include <asm/mmu.h> #include <asm/thread_info.h> +#include <asm/code-patching-asm.h> #include <asm/ppc_asm.h> #include <asm/asm-offsets.h> #include <asm/cputable.h> @@ -506,6 +507,57 @@ _GLOBAL(ret_from_kernel_thread) li r3,0 b .Lsyscall_exit +#ifdef CONFIG_PPC_BOOK3S_64 + +#define FLUSH_COUNT_CACHE \ +1: nop; \ + patch_site 1b, patch__call_flush_count_cache + + +#define BCCTR_FLUSH .long 0x4c400420 + +.macro nops number + .rept \number + nop + .endr +.endm + +.balign 32 +.global flush_count_cache +flush_count_cache: + /* Save LR into r9 */ + mflr r9 + + .rept 64 + bl .+4 + .endr + b 1f + nops 6 + + .balign 32 + /* Restore LR */ +1: mtlr r9 + li r9,0x7fff + mtctr r9 + + BCCTR_FLUSH + +2: nop + patch_site 2b patch__flush_count_cache_return + + nops 3 + + .rept 278 + .balign 32 + BCCTR_FLUSH + nops 7 + .endr + + blr +#else +#define FLUSH_COUNT_CACHE +#endif /* CONFIG_PPC_BOOK3S_64 */ + /* * This routine switches between two different tasks. The process * state of one is saved on its kernel stack. Then the state @@ -537,6 +589,8 @@ _GLOBAL(_switch) std r23,_CCR(r1) std r1,KSP(r3) /* Set old stack pointer */ + FLUSH_COUNT_CACHE + /* * On SMP kernels, care must be taken because a task may be * scheduled off CPUx and on to CPUy. Memory ordering must be |