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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Will Deacon <will.deacon@arm.com>, linux-arch@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, Will Deacon <will.deacon@arm.com>,
        "Paul E. McKenney" <paulmck@linux.ibm.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Andrea Parri <andrea.parri@amarulasolutions.com>,
        Palmer Dabbelt <palmer@sifive.com>,
        Daniel Lustig <dlustig@nvidia.com>,
        David Howells <dhowells@redhat.com>,
        Alan Stern <stern@rowland.harvard.edu>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "Maciej W. Rozycki" <macro@linux-mips.org>,
        Paul Burton <paul.burton@mips.com>,
        Ingo Molnar <mingo@kernel.org>,
        Yoshinori Sato <ysato@users.sourceforge.jp>,
        Rich Felker <dalias@libc.org>, Tony Luck <tony.luck@intel.com>
Subject: Re: [PATCH 12/20] powerpc/mmiowb: Hook up mmwiob() implementation to asm-generic code
In-Reply-To: <20190301140348.25175-13-will.deacon@arm.com>
References: <20190301140348.25175-1-will.deacon@arm.com> <20190301140348.25175-13-will.deacon@arm.com>
Date:   Sat, 02 Mar 2019 23:46:41 +1100
Message-ID: <874l8ljvf2.fsf@concordia.ellerman.id.au>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi Will,

Will Deacon <will.deacon@arm.com> writes:
> In a bid to kill off explicit mmiowb() usage in driver code, hook up
> the asm-generic mmiowb() tracking code but provide a definition of
> arch_mmiowb_state() so that the tracking data can remain in the paca
> as it does at present
>
> This replaces the existing (flawed) implementation.
>
> Signed-off-by: Will Deacon <will.deacon@arm.com>
> ---
>  arch/powerpc/Kconfig                |  1 +
>  arch/powerpc/include/asm/Kbuild     |  1 -
>  arch/powerpc/include/asm/io.h       | 33 +++------------------------------
>  arch/powerpc/include/asm/mmiowb.h   | 20 ++++++++++++++++++++
>  arch/powerpc/include/asm/paca.h     |  6 +++++-
>  arch/powerpc/include/asm/spinlock.h | 17 -----------------
>  arch/powerpc/xmon/xmon.c            |  5 ++++-
>  7 files changed, 33 insertions(+), 50 deletions(-)
>  create mode 100644 arch/powerpc/include/asm/mmiowb.h

Thanks for fixing our bugs for us, I owe you some more beers :)

I meant to reply to your previous series saying that we could just use
more space in the paca, but you obviously worked that out yourself.

I'll run this through our builders and do some boot tests but I looks
good to me.

Acked-by: Michael Ellerman <mpe@ellerman.id.au>


cheers


> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 2890d36eb531..6979304475fd 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -134,6 +134,7 @@ config PPC
>  	select ARCH_HAS_ELF_RANDOMIZE
>  	select ARCH_HAS_FORTIFY_SOURCE
>  	select ARCH_HAS_GCOV_PROFILE_ALL
> +	select ARCH_HAS_MMIOWB			if PPC64
>  	select ARCH_HAS_PHYS_TO_DMA
>  	select ARCH_HAS_PMEM_API                if PPC64
>  	select ARCH_HAS_PTE_SPECIAL
> diff --git a/arch/powerpc/include/asm/Kbuild b/arch/powerpc/include/asm/Kbuild
> index 57bd1f6660f4..77ff7fb24823 100644
> --- a/arch/powerpc/include/asm/Kbuild
> +++ b/arch/powerpc/include/asm/Kbuild
> @@ -8,7 +8,6 @@ generic-y += irq_regs.h
>  generic-y += irq_work.h
>  generic-y += local64.h
>  generic-y += mcs_spinlock.h
> -generic-y += mmiowb.h
>  generic-y += preempt.h
>  generic-y += rwsem.h
>  generic-y += vtime.h
> diff --git a/arch/powerpc/include/asm/io.h b/arch/powerpc/include/asm/io.h
> index 7f19fbd3ba55..828100476ba6 100644
> --- a/arch/powerpc/include/asm/io.h
> +++ b/arch/powerpc/include/asm/io.h
> @@ -34,14 +34,11 @@ extern struct pci_dev *isa_bridge_pcidev;
>  #include <asm/byteorder.h>
>  #include <asm/synch.h>
>  #include <asm/delay.h>
> +#include <asm/mmiowb.h>
>  #include <asm/mmu.h>
>  #include <asm/ppc_asm.h>
>  #include <asm/pgtable.h>
>  
> -#ifdef CONFIG_PPC64
> -#include <asm/paca.h>
> -#endif
> -
>  #define SIO_CONFIG_RA	0x398
>  #define SIO_CONFIG_RD	0x399
>  
> @@ -107,12 +104,6 @@ extern bool isa_io_special;
>   *
>   */
>  
> -#ifdef CONFIG_PPC64
> -#define IO_SET_SYNC_FLAG()	do { local_paca->io_sync = 1; } while(0)
> -#else
> -#define IO_SET_SYNC_FLAG()
> -#endif
> -
>  #define DEF_MMIO_IN_X(name, size, insn)				\
>  static inline u##size name(const volatile u##size __iomem *addr)	\
>  {									\
> @@ -127,7 +118,7 @@ static inline void name(volatile u##size __iomem *addr, u##size val)	\
>  {									\
>  	__asm__ __volatile__("sync;"#insn" %1,%y0"			\
>  		: "=Z" (*addr) : "r" (val) : "memory");			\
> -	IO_SET_SYNC_FLAG();						\
> +	mmiowb_set_pending();						\
>  }
>  
>  #define DEF_MMIO_IN_D(name, size, insn)				\
> @@ -144,7 +135,7 @@ static inline void name(volatile u##size __iomem *addr, u##size val)	\
>  {									\
>  	__asm__ __volatile__("sync;"#insn"%U0%X0 %1,%0"			\
>  		: "=m" (*addr) : "r" (val) : "memory");			\
> -	IO_SET_SYNC_FLAG();						\
> +	mmiowb_set_pending();						\
>  }
>  
>  DEF_MMIO_IN_D(in_8,     8, lbz);
> @@ -652,24 +643,6 @@ static inline void name at					\
>  
>  #include <asm-generic/iomap.h>
>  
> -#ifdef CONFIG_PPC32
> -#define mmiowb()
> -#else
> -/*
> - * Enforce synchronisation of stores vs. spin_unlock
> - * (this does it explicitly, though our implementation of spin_unlock
> - * does it implicitely too)
> - */
> -static inline void mmiowb(void)
> -{
> -	unsigned long tmp;
> -
> -	__asm__ __volatile__("sync; li %0,0; stb %0,%1(13)"
> -	: "=&r" (tmp) : "i" (offsetof(struct paca_struct, io_sync))
> -	: "memory");
> -}
> -#endif /* !CONFIG_PPC32 */
> -
>  static inline void iosync(void)
>  {
>          __asm__ __volatile__ ("sync" : : : "memory");
> diff --git a/arch/powerpc/include/asm/mmiowb.h b/arch/powerpc/include/asm/mmiowb.h
> new file mode 100644
> index 000000000000..b10180613507
> --- /dev/null
> +++ b/arch/powerpc/include/asm/mmiowb.h
> @@ -0,0 +1,20 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_POWERPC_MMIOWB_H
> +#define _ASM_POWERPC_MMIOWB_H
> +
> +#ifdef CONFIG_MMIOWB
> +
> +#include <linux/compiler.h>
> +#include <asm/barrier.h>
> +#include <asm/paca.h>
> +
> +#define arch_mmiowb_state()	(&local_paca->mmiowb_state)
> +#define mmiowb()		mb()
> +
> +#else
> +#define mmiowb()		do { } while (0)
> +#endif /* CONFIG_MMIOWB */
> +
> +#include <asm-generic/mmiowb.h>
> +
> +#endif	/* _ASM_POWERPC_MMIOWB_H */
> diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
> index e843bc5d1a0f..134e912d403f 100644
> --- a/arch/powerpc/include/asm/paca.h
> +++ b/arch/powerpc/include/asm/paca.h
> @@ -34,6 +34,8 @@
>  #include <asm/cpuidle.h>
>  #include <asm/atomic.h>
>  
> +#include <asm-generic/mmiowb_types.h>
> +
>  register struct paca_struct *local_paca asm("r13");
>  
>  #if defined(CONFIG_DEBUG_PREEMPT) && defined(CONFIG_SMP)
> @@ -171,7 +173,6 @@ struct paca_struct {
>  	u16 trap_save;			/* Used when bad stack is encountered */
>  	u8 irq_soft_mask;		/* mask for irq soft masking */
>  	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
> @@ -264,6 +265,9 @@ struct paca_struct {
>  #ifdef CONFIG_STACKPROTECTOR
>  	unsigned long canary;
>  #endif
> +#ifdef CONFIG_MMIOWB
> +	struct mmiowb_state mmiowb_state;
> +#endif
>  } ____cacheline_aligned;
>  
>  extern void copy_mm_to_paca(struct mm_struct *mm);
> diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h
> index 685c72310f5d..15b39c407c4e 100644
> --- a/arch/powerpc/include/asm/spinlock.h
> +++ b/arch/powerpc/include/asm/spinlock.h
> @@ -39,19 +39,6 @@
>  #define LOCK_TOKEN	1
>  #endif
>  
> -#if defined(CONFIG_PPC64) && defined(CONFIG_SMP)
> -#define CLEAR_IO_SYNC	(get_paca()->io_sync = 0)
> -#define SYNC_IO		do {						\
> -				if (unlikely(get_paca()->io_sync)) {	\
> -					mb();				\
> -					get_paca()->io_sync = 0;	\
> -				}					\
> -			} while (0)
> -#else
> -#define CLEAR_IO_SYNC
> -#define SYNC_IO
> -#endif
> -
>  #ifdef CONFIG_PPC_PSERIES
>  #define vcpu_is_preempted vcpu_is_preempted
>  static inline bool vcpu_is_preempted(int cpu)
> @@ -99,7 +86,6 @@ static inline unsigned long __arch_spin_trylock(arch_spinlock_t *lock)
>  
>  static inline int arch_spin_trylock(arch_spinlock_t *lock)
>  {
> -	CLEAR_IO_SYNC;
>  	return __arch_spin_trylock(lock) == 0;
>  }
>  
> @@ -130,7 +116,6 @@ extern void __rw_yield(arch_rwlock_t *lock);
>  
>  static inline void arch_spin_lock(arch_spinlock_t *lock)
>  {
> -	CLEAR_IO_SYNC;
>  	while (1) {
>  		if (likely(__arch_spin_trylock(lock) == 0))
>  			break;
> @@ -148,7 +133,6 @@ void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
>  {
>  	unsigned long flags_dis;
>  
> -	CLEAR_IO_SYNC;
>  	while (1) {
>  		if (likely(__arch_spin_trylock(lock) == 0))
>  			break;
> @@ -167,7 +151,6 @@ void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
>  
>  static inline void arch_spin_unlock(arch_spinlock_t *lock)
>  {
> -	SYNC_IO;
>  	__asm__ __volatile__("# arch_spin_unlock\n\t"
>  				PPC_RELEASE_BARRIER: : :"memory");
>  	lock->slock = 0;
> diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
> index 757b8499aba2..de8e4693b176 100644
> --- a/arch/powerpc/xmon/xmon.c
> +++ b/arch/powerpc/xmon/xmon.c
> @@ -2429,7 +2429,10 @@ static void dump_one_paca(int cpu)
>  	DUMP(p, trap_save, "%#-*x");
>  	DUMP(p, irq_soft_mask, "%#-*x");
>  	DUMP(p, irq_happened, "%#-*x");
> -	DUMP(p, io_sync, "%#-*x");
> +#ifdef CONFIG_MMIOWB
> +	DUMP(p, mmiowb_state.nesting_count, "%#-*x");
> +	DUMP(p, mmiowb_state.mmiowb_pending, "%#-*x");
> +#endif
>  	DUMP(p, irq_work_pending, "%#-*x");
>  	DUMP(p, nap_state_lost, "%#-*x");
>  	DUMP(p, sprg_vdso, "%#-*llx");
> -- 
> 2.11.0