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author | Nicholas Piggin <npiggin@gmail.com> | 2019-04-13 00:30:52 +1000 |
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committer | Michael Ellerman <mpe@ellerman.id.au> | 2019-04-30 22:37:48 +1000 |
commit | 10d91611f426d4bafd2a83d966c36da811b2f7ad (patch) | |
tree | e455d47497c64533f4537290dae97baae10d0340 /arch/powerpc/include/asm/paca.h | |
parent | c1fe190c06723322f2dfac31d3b982c581e434ef (diff) | |
download | linux-10d91611f426d4bafd2a83d966c36da811b2f7ad.tar.bz2 |
powerpc/64s: Reimplement book3s idle code in C
Reimplement Book3S idle code in C, moving POWER7/8/9 implementation
speific HV idle code to the powernv platform code.
Book3S assembly stubs are kept in common code and used only to save
the stack frame and non-volatile GPRs before executing architected
idle instructions, and restoring the stack and reloading GPRs then
returning to C after waking from idle.
The complex logic dealing with threads and subcores, locking, SPRs,
HMIs, timebase resync, etc., is all done in C which makes it more
maintainable.
This is not a strict translation to C code, there are some
significant differences:
- Idle wakeup no longer uses the ->cpu_restore call to reinit SPRs,
but saves and restores them itself.
- The optimisation where EC=ESL=0 idle modes did not have to save GPRs
or change MSR is restored, because it's now simple to do. ESL=1
sleeps that do not lose GPRs can use this optimization too.
- KVM secondary entry and cede is now more of a call/return style
rather than branchy. nap_state_lost is not required because KVM
always returns via NVGPR restoring path.
- KVM secondary wakeup from offline sequence is moved entirely into
the offline wakeup, which avoids a hwsync in the normal idle wakeup
path.
Performance measured with context switch ping-pong on different
threads or cores, is possibly improved a small amount, 1-3% depending
on stop state and core vs thread test for shallow states. Deep states
it's in the noise compared with other latencies.
KVM improvements:
- Idle sleepers now always return to caller rather than branch out
to KVM first.
- This allows optimisations like very fast return to caller when no
state has been lost.
- KVM no longer requires nap_state_lost because it controls NVGPR
save/restore itself on the way in and out.
- The heavy idle wakeup KVM request check can be moved out of the
normal host idle code and into the not-performance-critical offline
code.
- KVM nap code now returns from where it is called, which makes the
flow a bit easier to follow.
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Squash the KVM changes in]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/include/asm/paca.h')
-rw-r--r-- | arch/powerpc/include/asm/paca.h | 40 |
1 files changed, 22 insertions, 18 deletions
diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h index e843bc5d1a0f..245d11a71784 100644 --- a/arch/powerpc/include/asm/paca.h +++ b/arch/powerpc/include/asm/paca.h @@ -173,7 +173,6 @@ struct paca_struct { u8 irq_happened; /* irq happened while soft-disabled */ u8 io_sync; /* writel() needs spin_unlock sync */ u8 irq_work_pending; /* IRQ_WORK interrupt while soft-disable */ - u8 nap_state_lost; /* NV GPR values lost in power7_idle */ #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE u8 pmcregs_in_use; /* pseries puts this in lppaca */ #endif @@ -183,23 +182,28 @@ struct paca_struct { #endif #ifdef CONFIG_PPC_POWERNV - /* Per-core mask tracking idle threads and a lock bit-[L][TTTTTTTT] */ - u32 *core_idle_state_ptr; - u8 thread_idle_state; /* PNV_THREAD_RUNNING/NAP/SLEEP */ - /* Mask to indicate thread id in core */ - u8 thread_mask; - /* Mask to denote subcore sibling threads */ - u8 subcore_sibling_mask; - /* Flag to request this thread not to stop */ - atomic_t dont_stop; - /* The PSSCR value that the kernel requested before going to stop */ - u64 requested_psscr; - - /* - * Save area for additional SPRs that need to be - * saved/restored during cpuidle stop. - */ - struct stop_sprs stop_sprs; + /* PowerNV idle fields */ + /* PNV_CORE_IDLE_* bits, all siblings work on thread 0 paca */ + unsigned long idle_state; + union { + /* P7/P8 specific fields */ + struct { + /* PNV_THREAD_RUNNING/NAP/SLEEP */ + u8 thread_idle_state; + /* Mask to denote subcore sibling threads */ + u8 subcore_sibling_mask; + }; + + /* P9 specific fields */ + struct { +#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE + /* The PSSCR value that the kernel requested before going to stop */ + u64 requested_psscr; + /* Flag to request this thread not to stop */ + atomic_t dont_stop; +#endif + }; + }; #endif #ifdef CONFIG_PPC_BOOK3S_64 |