From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pegase2.c-s.fr (pegase2.c-s.fr [93.17.235.10]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 6A9F81CF5E2 for ; Tue, 28 Jan 2025 15:50:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=93.17.235.10 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738079405; cv=none; b=JNPIHpyHlcaGkrjzUlwScEiQxkbIL5w8pbHluXIaOk3clW+Ge2pwL+3RSjIYUvTo8VjEy1eJoYv2Qb+Wwk6+oBwO/ZF5jajPnJqYtUI6QuTwyhNkmisFmcSwBneGOZE2rHU3wTy1aNmqhiebCBmjbw1VFQ6tF3lygYbs3hnxvpU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738079405; c=relaxed/simple; bh=zA0p3GRgjBR6M7uaHu91lHy0qpqIRscx8EGPKDHqRw8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=U5wEyCSKNduc747o5oLo/Af5zLg113HeP+ewlBH/TTncYtxuhUj/vGqZaI1bNWUqbUZagajaD1jFA6TgmAGNSKgGwGxH1I28uHJ8SAgl0jfBDL1p7Ooa14reZg5ATHs1flRK8cDTc/yAwRgjcwu/KrgXki71HpVdSOuyXogu5p8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=csgroup.eu; spf=pass smtp.mailfrom=csgroup.eu; arc=none smtp.client-ip=93.17.235.10 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=csgroup.eu Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=csgroup.eu Received: from localhost (mailhub3.si.c-s.fr [172.26.127.67]) by localhost (Postfix) with ESMTP id 4Yj8GJ02Vrz9sTD; Tue, 28 Jan 2025 16:24:24 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from pegase2.c-s.fr ([172.26.127.65]) by localhost (pegase2.c-s.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ESV36a5BhAvE; Tue, 28 Jan 2025 16:24:23 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase2.c-s.fr (Postfix) with ESMTP id 4Yj8Fz6NQdz9sTk; Tue, 28 Jan 2025 16:24:07 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id CB3EE8B76C; Tue, 28 Jan 2025 16:24:07 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id 6ToQVNIjR5TM; Tue, 28 Jan 2025 16:24:07 +0100 (CET) Received: from [192.168.235.99] (unknown [192.168.235.99]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 557E08B763; Tue, 28 Jan 2025 16:24:07 +0100 (CET) Message-ID: Date: Tue, 28 Jan 2025 16:24:07 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] powerpc: Remove eieio in _memcpy_fromio To: Julian Vetter , Arnd Bergmann , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Naveen N Rao Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org References: <20250128135711.1625747-1-julian@outer-limits.org> <81ee3098-1e43-4b88-975a-d223bc2338e8@csgroup.eu> Content-Language: fr-FR From: Christophe Leroy In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Le 28/01/2025 à 16:07, Julian Vetter a écrit : > [Vous ne recevez pas souvent de courriers de julian@outer-limits.org. > Découvrez pourquoi ceci est important à https://aka.ms/ > LearnAboutSenderIdentification ] > > On 1/28/25 15:16, Christophe Leroy wrote: >> >> >> Le 28/01/2025 à 14:57, Julian Vetter a écrit : >>> Remove the eieio() calls in _memcpy_fromio, to bring its implementation >>> closer to the one from lib/iomem_copy.c. These eieio() calls don't seem >>> to be necessary, because the _memcpy_toio completely omits them. Also >>> the legacy code from ppc was not doing them. >> >> What do you mean exactly by "legacy code" ? >> >> As far as I can see they were already there before commit 68a64357d15a >> ("[POWERPC] Merge 32 and 64 bits asm-powerpc/io.h"): >> > > With 'ppc' I was refering to 'include/asm-ppc/io.h'. But you're right, > when going back a bit, in the 'include/asm-powerpc/io.h' there are two > cases, one (eeh_memcpy_fromio) which does the the 'eieio', and a second, > i.e., 'iSeries_memcpy_fromio' which does a byte-wise copy. But in the > ppc code ('include/asm-ppc/io.h') there is a simple memcpy. I was > referring to this one. But my description is not very clear. Sorry for > that. But then is your change still valid ? Isn't there some corner case that still need it ? Is it a valid argument that because memcpy_toio() doesn't need it memcpy_fromio() doesn't need it either ? > >> -static inline void eeh_memcpy_fromio(void *dest, const volatile void >> __iomem *src, >> +static inline void eeh_memcpy_fromio(void *dest, const >> +                     volatile void __iomem *src, >>                        unsigned long n) >>   { >> -    void *vsrc = (void __force *) src; >> -    void *destsave = dest; >> -    unsigned long nsave = n; >> - >> -    __asm__ __volatile__ ("sync" : : : "memory"); >> -    while(n && (!EEH_CHECK_ALIGN(vsrc, 4) || !EEH_CHECK_ALIGN(dest, >> 4))) { >> -        *((u8 *)dest) = *((volatile u8 *)vsrc); >> -        __asm__ __volatile__ ("eieio" : : : "memory"); >> -        vsrc++; >> -        dest++; >> -        n--; >> -    } >> -    while(n > 4) { >> -        *((u32 *)dest) = *((volatile u32 *)vsrc); >> -        __asm__ __volatile__ ("eieio" : : : "memory"); >> -        vsrc += 4; >> -        dest += 4; >> -        n -= 4; >> -    } >> -    while(n) { >> -        *((u8 *)dest) = *((volatile u8 *)vsrc); >> -        __asm__ __volatile__ ("eieio" : : : "memory"); >> -        vsrc++; >> -        dest++; >> -        n--; >> -    } >> -    __asm__ __volatile__ ("sync" : : : "memory"); >> +    _memcpy_fromio(dest, src, n); >> >>       /* Look for ffff's here at dest[n].  Assume that at least 4 bytes >>        * were copied. Check all four bytes. >>        */ >> -    if ((nsave >= 4) && >> -        (EEH_POSSIBLE_ERROR((*((u32 *) destsave+nsave-4)), u32))) { >> -        eeh_check_failure(src, (*((u32 *) destsave+nsave-4))); >> -    } >> +    if (n >= 4 && EEH_POSSIBLE_ERROR(*((u32 *)(dest + n - 4)), u32)) >> +        eeh_check_failure(src, *((u32 *)(dest + n - 4))); >>   } >> >> >> >>> >>> Signed-off-by: Julian Vetter >>> --- >>>   arch/powerpc/kernel/io.c | 3 --- >>>   1 file changed, 3 deletions(-) >>> >>> diff --git a/arch/powerpc/kernel/io.c b/arch/powerpc/kernel/io.c >>> index 6af535905984..81e5d54260a1 100644 >>> --- a/arch/powerpc/kernel/io.c >>> +++ b/arch/powerpc/kernel/io.c >>> @@ -155,21 +155,18 @@ void _memcpy_fromio(void *dest, const volatile >>> void __iomem *src, >>>          __asm__ __volatile__ ("sync" : : : "memory"); >>>          while(n && (!IO_CHECK_ALIGN(vsrc, 4) || !IO_CHECK_ALIGN(dest, >>> 4))) { >>>                  *((u8 *)dest) = *((volatile u8 *)vsrc); >>> -               eieio(); >>>                  vsrc++; >>>                  dest++; >>>                  n--; >>>          } >>>          while(n >= 4) { >>>                  *((u32 *)dest) = *((volatile u32 *)vsrc); >>> -               eieio(); >>>                  vsrc += 4; >>>                  dest += 4; >>>                  n -= 4; >>>          } >>>          while(n) { >>>                  *((u8 *)dest) = *((volatile u8 *)vsrc); >>> -               eieio(); >>>                  vsrc++; >>>                  dest++; >>>                  n--; >>> -- >>> 2.34.1 >>> >>