From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-110.freemail.mail.aliyun.com (out30-110.freemail.mail.aliyun.com [115.124.30.110]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0B9F13CEBB1 for ; Wed, 9 Sep 2026 09:22:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.110 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788945775; cv=none; b=mnFVA4ZqQeGdpQtbzjfsMprdh0g5P4jF3WPmsto8a76Xfcpj07yQYOw0NJu4nMNzUQYvVPAMtbVjsY5ri+BAV/X4XkVNEhuyX57IYMQkA/RnvkVlnARNi/4wOSOV7hEo8p33rhWi4ldAFmtqqNUjGDHIY5lTgTZnQipxQMVswWc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788945775; c=relaxed/simple; bh=i0/WKycaG9HSpOn9oRuJpFAIa9d+AWJNfR9gdzLM154=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=LcUVu8Pleb4dYJ0TX9zPJffy2O4uQsbjggXEs+2jTcqNR4rluFvdVhYx8JXrBo3UXOO6ZybCrUKfXZCCIp9DqdTz9fWTtDlAX8fg0WqVAW7gtC4jLXyNKtUW7V3bd59W5+2xr4rVPPNiD7m1wzP633fNEN3dp5T64G0FuHqAndk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=aqueN7Oc; arc=none smtp.client-ip=115.124.30.110 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="aqueN7Oc" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1788945770; h=Message-ID:Date:MIME-Version:Subject:From:To:Content-Type; bh=Xpuxu9v+M+U3EVPLB4MIjbtLCINO5kVa9rmGoxL+8W8=; b=aqueN7OcgnDQDrFyjZkiYuQ2KUXRuhEi2Z84YLxyVP2tzUQ61QWzO0w6JN8qqW2e1YtsudVSyEbxqrWxnkiEwMUgXYzKjqN8jyhkRtnOySNIpJc5fS7Pm867keU/cZ10QSnFcw6e8ki0iAUaK6Nyq5Voh+nWIyS3usLbWGwaPjM= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R531e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033037026112;MF=kanie@linux.alibaba.com;NM=1;PH=DS;RN=9;SR=0;TI=SMTPD_---0XAeT4fc_1788945769; Received: from 30.178.68.218(mailfrom:kanie@linux.alibaba.com fp:SMTPD_---0XAeT4fc_1788945769 cluster:ay36) by smtp.aliyun-inc.com; Wed, 09 Sep 2026 17:22:50 +0800 Message-ID: <8a016242-35fe-48af-a305-c4ec03b79537@linux.alibaba.com> Date: Wed, 9 Sep 2026 17:22:48 +0800 Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5] cxl/pci: Skip reset detection for DVSEC emulated decoders From: Guixin Liu To: Davidlohr Bueso , Jonathan Cameron , Dave Jiang , Alison Schofield , Vishal Verma , Dan Williams , Ira Weiny , Li Ming Cc: linux-cxl@vger.kernel.org References: <20260831110449.719086-1-kanie@linux.alibaba.com> In-Reply-To: <20260831110449.719086-1-kanie@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi,gentle ping on this patch. Any feedback would be appreciated. thanks. Best Regards, Guixin Liu 在 2026/8/31 19:04, Guixin Liu 写道: > HDM decoders are emulated from the DVSEC range registers in two cases: > (a) the component registers expose no HDM decoder capability, or (b) the > capability is present but the DVSEC ranges were the ones in use at driver > load. > > After an FLR or SBR, __cxl_endpoint_decoder_reset_detected() reads the HDM > decoder Committed bit for every decoder marked enabled, emulated ones > included. In case (a) regs.hdm_decoder is NULL and the read oopses. In case > (b) the Committed bit was never set, so a reset gets reported that never > happened. > > Use the absence of cxld->commit to elide the check for emulated decoders. > > Case (b) tested under QEMU: a reset on an endpoint driven down the DVSEC > emulation path no longer reports a reset or strips the decoder flags. > > Fixes: 934edcd436dc ("cxl: Add post-reset warning if reset results in loss of previously committed HDM decoders") > Signed-off-by: Guixin Liu > Reviewed-by: Jonathan Cameron > --- > This was patch 4/8 of the "cxl: Assorted fixes" series [1], resent > individually per review feedback. > > The two synchronisation concerns the review bot raised on v2 - the missing > exclusion against a cxl_port unbind freeing the devm allocated cxl_hdm, and > the plain read-modify-write of cxld->flags in > cxl_endpoint_decoder_clear_reset_flags() while the region paths update the > same word under cxl_rwsem.region - are still untouched here. Both are > about the reset handler's locking rather than about which registers it > reads, and neither fix is local; happy to follow up with separate patches. > > Testing > > Reaching case (b) needs an endpoint whose DVSEC ranges are live while the > global HDM decoder enable is clear. Unbinding cxl_pci runs the > disable_hdm() and clear_mem_enable() devm actions, so both bits start > clean. setpci then programs DVSEC Range 1 Base to 0x890000000, which sits > inside a RAM capable CFMWS, and sets Mem_Enable. Rebinding takes the > emulation path: > > cxl_port endpoint3: Fallback map 1 range register > cxl_pci 0000:35:00.0: DVSEC Range0 allowed by platform > > The endpoint ends up with a single decoder, enabled and locked, with no > Committed bit behind it: > > decoder3.0: locked=1 start=0x890000000 size=0x100000000 mode=ram > > The device's only available reset method is cxl_bus, which unmasks SBR > through the port DVSEC. Before this change: > > cxl_pci 0000:35:00.0: resetting > cxl_pci 0000:35:00.0: SBR happened without memory regions removal. > cxl_pci 0000:35:00.0: System may be unstable if regions hosted system memory. > > /proc/sys/kernel/tainted picked up TAINT_USER (8192 -> 8256) and locked > dropped from 1 to 0. After this change the same reset logs only > "resetting", locked stays 1, and no taint is added. The decoder is > decoder6.0 in the second run because reloading cxl_core renumbered the > memdevs. > > QEMU does not clear the DVSEC range registers on SBR, so the emulated > decode is still fully programmed by the time the reset completes. The old > report was spurious here too. > > Not covered: case (a) needs an endpoint with no component register block, > which QEMU's type3 always provides, and the FLR variant needs FLR support > that QEMU's type3 does not advertise (FLReset-). I also did not run a > positive control confirming that a normally committed HDM decoder is still > detected after this change. > > v1->v2: > - rebase onto cxl/next > - rewrite the commit message to describe the behaviour rather than narrate > the code change (Alison Schofield) > > v2->v3: > - test cxld->commit instead of cxlhdm->regs.hdm_decoder, so that decoders > emulated from the DVSEC ranges are also skipped when the HDM decoder > registers exist but are globally disabled (Richard Cheng) > - update the subject and the commit message for the widened scope > > v3->v4: > - shorten the commit message (Dave Jiang) > > v4->v5: > - condense the commit message further, wording taken from Jonathan > Cameron's suggestion on v4 > - note the case (b) test in the commit message > > [1] https://lore.kernel.org/linux-cxl/20260811113608.2815625-1-kanie@linux.alibaba.com/ > > drivers/cxl/core/pci.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c > index 9d807c1a002c..d8b07f86bab0 100644 > --- a/drivers/cxl/core/pci.c > +++ b/drivers/cxl/core/pci.c > @@ -683,6 +683,13 @@ static int __cxl_endpoint_decoder_reset_detected(struct device *dev, void *data) > if ((cxld->flags & CXL_DECODER_F_ENABLE) == 0) > return 0; > > + /* > + * Decoders emulated from the DVSEC range registers have no commit > + * callback and no HDM decoder registers to consult. > + */ > + if (!cxld->commit) > + return 0; > + > cxlhdm = dev_get_drvdata(&port->dev); > hdm = cxlhdm->regs.hdm_decoder; > ctrl = readl(hdm + CXL_HDM_DECODER0_CTRL_OFFSET(cxld->id)); > > base-commit: 7098e9cd98a05c0c5de2fae0c2465f9d966fdd07