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powerpc/64s: system call support for scv/rfscv instructions

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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
This commit is contained in:
Nicholas Piggin
2020-06-11 18:12:03 +10:00
committed by Michael Ellerman
parent b2dc2977cb
commit 7fa95f9ada
20 changed files with 422 additions and 45 deletions
Download Patch File Download Diff File Expand all files Collapse all files

32
arch/powerpc/kernel/syscall_64.c
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@@ -60,6 +60,11 @@ notrace long system_call_exception(long r3, long r4, long r5,
local_irq_enable();
if (unlikely(current_thread_info()->flags & _TIF_SYSCALL_DOTRACE)) {
if (unlikely(regs->trap == 0x7ff0)) {
/* Unsupported scv vector */
_exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
return regs->gpr[3];
}
/*
* We use the return value of do_syscall_trace_enter() as the
* syscall number. If the syscall was rejected for any reason
@@ -78,6 +83,11 @@ notrace long system_call_exception(long r3, long r4, long r5,
r8 = regs->gpr[8];
} else if (unlikely(r0 >= NR_syscalls)) {
if (unlikely(regs->trap == 0x7ff0)) {
/* Unsupported scv vector */
_exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
return regs->gpr[3];
}
return -ENOSYS;
}
@@ -105,16 +115,20 @@ notrace long system_call_exception(long r3, long r4, long r5,
* local irqs must be disabled. Returns false if the caller must re-enable
* them, check for new work, and try again.
*/
static notrace inline bool prep_irq_for_enabled_exit(void)
static notrace inline bool prep_irq_for_enabled_exit(bool clear_ri)
{
/* This must be done with RI=1 because tracing may touch vmaps */
trace_hardirqs_on();
/* This pattern matches prep_irq_for_idle */
__hard_EE_RI_disable();
if (clear_ri)
__hard_EE_RI_disable();
else
__hard_irq_disable();
if (unlikely(lazy_irq_pending_nocheck())) {
/* Took an interrupt, may have more exit work to do. */
__hard_RI_enable();
if (clear_ri)
__hard_RI_enable();
trace_hardirqs_off();
local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
@@ -136,7 +150,8 @@ static notrace inline bool prep_irq_for_enabled_exit(void)
* because RI=0 and soft mask state is "unreconciled", so it is marked notrace.
*/
notrace unsigned long syscall_exit_prepare(unsigned long r3,
struct pt_regs *regs)
struct pt_regs *regs,
long scv)
{
unsigned long *ti_flagsp = &current_thread_info()->flags;
unsigned long ti_flags;
@@ -151,7 +166,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
ti_flags = *ti_flagsp;
if (unlikely(r3 >= (unsigned long)-MAX_ERRNO)) {
if (unlikely(r3 >= (unsigned long)-MAX_ERRNO) && !scv) {
if (likely(!(ti_flags & (_TIF_NOERROR | _TIF_RESTOREALL)))) {
r3 = -r3;
regs->ccr |= 0x10000000; /* Set SO bit in CR */
@@ -211,7 +226,8 @@ again:
}
}
if (unlikely(!prep_irq_for_enabled_exit())) {
/* scv need not set RI=0 because SRRs are not used */
if (unlikely(!prep_irq_for_enabled_exit(!scv))) {
local_irq_enable();
goto again;
}
@@ -282,7 +298,7 @@ again:
}
}
if (unlikely(!prep_irq_for_enabled_exit())) {
if (unlikely(!prep_irq_for_enabled_exit(true))) {
local_irq_enable();
local_irq_disable();
goto again;
@@ -345,7 +361,7 @@ again:
}
}
if (unlikely(!prep_irq_for_enabled_exit())) {
if (unlikely(!prep_irq_for_enabled_exit(true))) {
/*
* Can't local_irq_restore to replay if we were in
* interrupt context. Must replay directly.