diff options
| author | Nicholas Piggin <npiggin@gmail.com> | 2020-06-11 18:12:03 +1000 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2020-07-22 23:00:27 +1000 |
| commit | 7fa95f9adaee7e5cbb195d3359741120829e488b (patch) | |
| tree | 1ca2d65102ad2c5223afe9a78e3105836982479f /arch/powerpc/kernel/process.c | |
| parent | b2dc2977cba48990df45e0a96150663d4f342700 (diff) | |
powerpc/64s: system call support for scv/rfscv instructions
Add support for the scv instruction on POWER9 and later CPUs.
For now this implements the zeroth scv vector 'scv 0', as identical to
'sc' system calls, with the exception that LR is not preserved, nor
are volatile CR registers, and error is not indicated with CR0[SO],
but by returning a negative errno.
rfscv is implemented to return from scv type system calls. It can not
be used to return from sc system calls because those are defined to
preserve LR.
getpid syscall throughput on POWER9 is improved by 26% (428 to 318
cycles), largely due to reducing mtmsr and mtspr.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Fix ppc64e build]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200611081203.995112-3-npiggin@gmail.com
Diffstat (limited to 'arch/powerpc/kernel/process.c')
| -rw-r--r-- | arch/powerpc/kernel/process.c | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 4650b9bb217f..939935613cf1 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -1599,6 +1599,7 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long usp, { struct pt_regs *childregs, *kregs; extern void ret_from_fork(void); + extern void ret_from_fork_scv(void); extern void ret_from_kernel_thread(void); void (*f)(void); unsigned long sp = (unsigned long)task_stack_page(p) + THREAD_SIZE; @@ -1635,7 +1636,9 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long usp, if (usp) childregs->gpr[1] = usp; p->thread.regs = childregs; - childregs->gpr[3] = 0; /* Result from fork() */ + /* 64s sets this in ret_from_fork */ + if (!IS_ENABLED(CONFIG_PPC_BOOK3S_64)) + childregs->gpr[3] = 0; /* Result from fork() */ if (clone_flags & CLONE_SETTLS) { if (!is_32bit_task()) childregs->gpr[13] = tls; @@ -1643,7 +1646,10 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long usp, childregs->gpr[2] = tls; } - f = ret_from_fork; + if (trap_is_scv(regs)) + f = ret_from_fork_scv; + else + f = ret_from_fork; } childregs->msr &= ~(MSR_FP|MSR_VEC|MSR_VSX); sp -= STACK_FRAME_OVERHEAD; |