From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0D05FEB64D8 for ; Wed, 14 Jun 2023 05:57:56 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=rYYjExOe; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4Qgvpp3tbPz30ht for ; Wed, 14 Jun 2023 15:57:54 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=rYYjExOe; dkim-atps=neutral Received: from gandalf.ozlabs.org (mail.ozlabs.org [IPv6:2404:9400:2221:ea00::3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4Qgvnq6r12z300q for ; Wed, 14 Jun 2023 15:57:03 +1000 (AEST) Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 4Qgvnl6MVqz4x1d; Wed, 14 Jun 2023 15:56:59 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ellerman.id.au; s=201909; t=1686722219; bh=NJMCszZ2hm+epJD/b0/Po9iHFnpLLa6pwtEYRGUJdg4=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=rYYjExOevnMF7VSK016ySJJkxyfYKfvocJ/hE9AX27BM+sOECgHU0HNhYT0O7nrN2 vyDzsumvC+wkHAcKJM+8UrMsqA266ztoQ/59pPNwQB1T8asqzDUa8Tgj7K3iFutMWg nYpSZcN5oE2tXc3B7f+r9vShGxjta70K78hmp6Lz+vqLmnDCD/tocmltGAr2whGjb+ LtBcZXJ8L/FCfjm/l7navUSEV0SoS8ZujmZrq+DBaPZrQ/zqq1cU49Rx6BCmTVku1X SP+KChTEHC5vebS5t5to/Gw66pgAILz6q+h19qAcEm7yMzaWvOaQwn38y/pwKRP4e4 br12yYv5yvMYA== From: Michael Ellerman To: Nicholas Piggin , linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 4/4] powerpc/64s: Use POWER10 stsync barrier for wmb() In-Reply-To: <87wn07foos.fsf@mail.lhotse> References: <20230609100026.8946-1-npiggin@gmail.com> <20230609100026.8946-4-npiggin@gmail.com> <87wn07foos.fsf@mail.lhotse> Date: Wed, 14 Jun 2023 15:56:57 +1000 Message-ID: <87ttvafuxi.fsf@mail.lhotse> MIME-Version: 1.0 Content-Type: text/plain X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Nicholas Piggin Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Michael Ellerman writes: > Nicholas Piggin writes: >> The most expensive ordering for hwsync to provide is the store-load >> barrier, because all prior stores have to be drained to the caches >> before subsequent instructions can complete. >> >> stsync just orders stores which means it can just be a barrer that >> goes down the store queue and orders draining, and does not prevent >> completion of subsequent instructions. So it should be faster than >> hwsync. >> >> Use stsync for wmb(). Older processors that don't recognise the SC >> field should treat this as hwsync. > > qemu (7.1) emulating ppc64e does not :/ > > mpic: Setting up MPIC " OpenPIC " version 1.2 at fe0040000, max 1 CPUs > mpic: ISU size: 256, shift: 8, mask: ff > mpic: Initializing for 256 sources > Oops: Exception in kernel mode, sig: 4 [#1] .. > > I guess just put it behind an #ifdef 64S. That doesn't work because qemu emulating a G5 also doesn't accept it. So either we need to get qemu updated and wait a while for that to percolate, or do some runtime patching of wmbs in the kernel >_< cheers