From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f49.google.com (mail-wm1-f49.google.com [209.85.128.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 86917341058 for ; Mon, 5 Jan 2026 13:40:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.49 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767620439; cv=none; b=YqHbziXpDDagfLtgDSSQvALbcGmIh9Ic1L5zvTryJ5L6XJBMJQ2cFqV3ciM00Kw1qeUyibnolB1v4yYy1Mfp5nQuUkcOD0Bvlk4WOQjGxN4Egsngqs5FfTEe+bz7YklteyKvayDJ3YYzs87+srtpDbepANeRP0UkQslA5eeweVU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767620439; c=relaxed/simple; bh=x4FbGO9rb3oDBd7srLGxGoyKvyyHdSRpv19OZNd+OHs=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=XWBlQ0xYP3UJ5QY8dMxkUjrGzHsdbmWR0NnRlMkKhU6QMzV+r5a4Tyg1NUiFCMh2xHmGd1LsMOKD6UJYPWIYRaIc8BYtFeQNd2TE3dq1jcaJTlCUWyxKBWOxuZ3Tg2FhBS3y8rUnYwhLhO7DKDW5AuCGK2qDex3oVjix8/L6VuU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com; spf=pass smtp.mailfrom=suse.com; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b=evTaGoQ9; arc=none smtp.client-ip=209.85.128.49 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b="evTaGoQ9" Received: by mail-wm1-f49.google.com with SMTP id 5b1f17b1804b1-4779d8286d8so10634715e9.0 for ; Mon, 05 Jan 2026 05:40:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1767620435; x=1768225235; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=f1KqtsDg02Q4tg0OrM0LKqtAMxJWRmTEsyj+AQ7lEeQ=; b=evTaGoQ9l965cOyOTnh5VeYas0tCw9526mqa7n8ccT6uk26o1WsIjbUtdKQbDGbx4d G2GkqZOAzx3cG8kDJBRARj1WHAcZp8JBG6V2+xoKtykO4SQSvnFxlQdkrRGYiPmjojNe IdwH0iXrrYMhGOenSzOtBl69bfNzL4tIb/SQ1uszrJUVD4UZBKvBq7VjOkxVT86eauBU fu3Rs0ay8tUh2p57vfgbGKbnK/vsXvASvojK4Kd7UM7Z3+BcDXgn5VILNDkNGCnCHFYk jsL3Dpvs/yOtHsxPsOy2suz8e6pLKLJm8DEMC/vfNW05+rfyc9ywYYRerKXn/pw9sK+K 8gjw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1767620435; x=1768225235; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=f1KqtsDg02Q4tg0OrM0LKqtAMxJWRmTEsyj+AQ7lEeQ=; b=MFHH5lw1PrSe0R2wy69zWeA59MfxPrqf/Vy3np8gpB2gMwTFSM6KWkzfSfC6igypfE priRWIqje9HMtseX22L9qhbLHF6s8uSqKxcnBgCpoZHnxtUI7W3FKP2/598o2q4trAmg qDgfR6IhXJCry3pH9xwH0188hC6bvFoZmG/atjkxtCsjo1t0nK/cyH1bUd68kPYIbCAQ qt/+TVfvm3Le3PzczZs9ir531+3AlBWtS2EFdZNVd9itYIU38hur+YASW2hnGRKjVfhy OncAoACA9kbArz5DzNrqzC3k5vYZhQMaB0FBgkb1tQHAFP5+3JMkxsY+OtFikFTxGGsz HMeA== X-Forwarded-Encrypted: i=1; AJvYcCVaoQTim2Y3bzqJplMtF4WMOtM7k8HlytJC9BPfXDndjYnYjPBJO/aZxdaijiGzbdfwLsdCzmx/45DB@vger.kernel.org X-Gm-Message-State: AOJu0YyE8HAJrULvvEehDD0oQ/hkOW7Vxwk8YnKZfTHskS1yIkYq9fuV qmJ6L2A6PP1Nj9FXPB5NjT94POmOn8KlB5E/bfuO+q7rAbde1T0QrYW4HZet4PEh+mk= X-Gm-Gg: AY/fxX4kpzKhuyroHTKWfGAJEqNDUKW3N8B00cFgQV9euGa4C70xpzeM4ncXFMrTGYg hTKizZ0Uiidxz0VZ4QR8dJ9/rGVOUv/39ol9HiuVbzbF2Pml4wfnG4kX83u82z7VrCNR3CDFRGI ejyMSZq/ZoPJL/S52jilntXWj3nQ1DyHrUECrRe1LGN4jIXd/jzPEuFFheZhXkznXKTLU4Q8ssz RDVCwVTZX+Cbi91m/c/Fm0yeHst4vu74gvq9KgpKGrlTCeQo511sc8ngN1LusLl3EOhdGRA/1DS I+n6prTxuvQDBvHP84pWwOcL5S54fRMaABT23QpCtHioRfi4fOnb9Z6QWaUcTkt7ituixLYUHsl jscsfWCrM8LOEv1bgpFHX0tfjt9q5ZKAb1BePNOUNmRBgNJ/ob8MkwyqcOHJPK7FYGZ4j46GjxV cLDEYBxEvI00K5wJFW19zqtkOfYflejRLFb4ztZQO0GifM6yER8HYaTiuT/8gt/WEDED8uARmP4 oW3 X-Google-Smtp-Source: AGHT+IFwXSkFSnAzDpXmvBfpaag5Ig2x/hY7lR/fPaiKG8l/aTMnGjVbJNKYUdmZgkyBxJqwrNsd/A== X-Received: by 2002:a05:600c:4ed2:b0:477:9c9e:ec7e with SMTP id 5b1f17b1804b1-47d19597517mr371677315e9.6.1767620434763; Mon, 05 Jan 2026 05:40:34 -0800 (PST) Received: from mordecai (dynamic-2a00-1028-83b8-1e7a-3010-3bd6-8521-caf1.ipv6.o2.cz. [2a00:1028:83b8:1e7a:3010:3bd6:8521:caf1]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47d6be2ce32sm61878015e9.2.2026.01.05.05.40.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 05 Jan 2026 05:40:34 -0800 (PST) Date: Mon, 5 Jan 2026 14:40:31 +0100 From: Petr Tesarik To: "Michael S. Tsirkin" Cc: linux-kernel@vger.kernel.org, Cong Wang , Jonathan Corbet , Olivia Mackall , Herbert Xu , Jason Wang , Paolo Bonzini , Stefan Hajnoczi , Eugenio =?UTF-8?B?UMOpcmV6?= , "James E.J. Bottomley" , "Martin K. Petersen" , Gerd Hoffmann , Xuan Zhuo , Marek Szyprowski , Robin Murphy , Stefano Garzarella , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Leon Romanovsky , Jason Gunthorpe , Bartosz Golaszewski , linux-doc@vger.kernel.org, linux-crypto@vger.kernel.org, virtualization@lists.linux.dev, linux-scsi@vger.kernel.org, iommu@lists.linux.dev, kvm@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH v2 05/15] dma-debug: track cache clean flag in entries Message-ID: <20260105144031.2520c81b@mordecai> In-Reply-To: <20260105073621-mutt-send-email-mst@kernel.org> References: <0ffb3513d18614539c108b4548cdfbc64274a7d1.1767601130.git.mst@redhat.com> <20260105105433.5b875ce3@mordecai> <20260105073621-mutt-send-email-mst@kernel.org> X-Mailer: Claws Mail 4.3.1 (GTK 3.24.51; x86_64-suse-linux-gnu) Precedence: bulk X-Mailing-List: linux-scsi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 5 Jan 2026 07:37:31 -0500 "Michael S. Tsirkin" wrote: > On Mon, Jan 05, 2026 at 10:54:33AM +0100, Petr Tesarik wrote: > > On Mon, 5 Jan 2026 03:23:10 -0500 > > "Michael S. Tsirkin" wrote: > > > > > If a driver is buggy and has 2 overlapping mappings but only > > > sets cache clean flag on the 1st one of them, we warn. > > > But if it only does it for the 2nd one, we don't. > > > > > > Fix by tracking cache clean flag in the entry. > > > > > > Signed-off-by: Michael S. Tsirkin > > > --- > > > kernel/dma/debug.c | 27 ++++++++++++++++++++++----- > > > 1 file changed, 22 insertions(+), 5 deletions(-) > > > > > > diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c > > > index 7e66d863d573..43d6a996d7a7 100644 > > > --- a/kernel/dma/debug.c > > > +++ b/kernel/dma/debug.c > > > @@ -63,6 +63,7 @@ enum map_err_types { > > > * @sg_mapped_ents: 'mapped_ents' from dma_map_sg > > > * @paddr: physical start address of the mapping > > > * @map_err_type: track whether dma_mapping_error() was checked > > > + * @is_cache_clean: driver promises not to write to buffer while mapped > > > * @stack_len: number of backtrace entries in @stack_entries > > > * @stack_entries: stack of backtrace history > > > */ > > > @@ -76,7 +77,8 @@ struct dma_debug_entry { > > > int sg_call_ents; > > > int sg_mapped_ents; > > > phys_addr_t paddr; > > > - enum map_err_types map_err_type; > > > + enum map_err_types map_err_type; > > > > *nitpick* unnecessary change in white space (breaks git-blame). > > > > Other than that, LGTM. I'm not formally a reviewer, but FWIW: > > > > Reviewed-by: Petr Tesarik > > > > Petr T > > > I mean, yes it's not really required here, but the padding we had before > was broken (two spaces not aligning to anything). Oh, you're right! Yes, then let's fix it now, because you touch the neighbouring line. Sorry for the noise. Petr T > > > + bool is_cache_clean; > > > #ifdef CONFIG_STACKTRACE > > > unsigned int stack_len; > > > unsigned long stack_entries[DMA_DEBUG_STACKTRACE_ENTRIES]; > > > @@ -472,12 +474,15 @@ static int active_cacheline_dec_overlap(phys_addr_t cln) > > > return active_cacheline_set_overlap(cln, --overlap); > > > } > > > > > > -static int active_cacheline_insert(struct dma_debug_entry *entry) > > > +static int active_cacheline_insert(struct dma_debug_entry *entry, > > > + bool *overlap_cache_clean) > > > { > > > phys_addr_t cln = to_cacheline_number(entry); > > > unsigned long flags; > > > int rc; > > > > > > + *overlap_cache_clean = false; > > > + > > > /* If the device is not writing memory then we don't have any > > > * concerns about the cpu consuming stale data. This mitigates > > > * legitimate usages of overlapping mappings. > > > @@ -487,8 +492,16 @@ static int active_cacheline_insert(struct dma_debug_entry *entry) > > > > > > spin_lock_irqsave(&radix_lock, flags); > > > rc = radix_tree_insert(&dma_active_cacheline, cln, entry); > > > - if (rc == -EEXIST) > > > + if (rc == -EEXIST) { > > > + struct dma_debug_entry *existing; > > > + > > > active_cacheline_inc_overlap(cln); > > > + existing = radix_tree_lookup(&dma_active_cacheline, cln); > > > + /* A lookup failure here after we got -EEXIST is unexpected. */ > > > + WARN_ON(!existing); > > > + if (existing) > > > + *overlap_cache_clean = existing->is_cache_clean; > > > + } > > > spin_unlock_irqrestore(&radix_lock, flags); > > > > > > return rc; > > > @@ -583,20 +596,24 @@ DEFINE_SHOW_ATTRIBUTE(dump); > > > */ > > > static void add_dma_entry(struct dma_debug_entry *entry, unsigned long attrs) > > > { > > > + bool overlap_cache_clean; > > > struct hash_bucket *bucket; > > > unsigned long flags; > > > int rc; > > > > > > + entry->is_cache_clean = !!(attrs & DMA_ATTR_CPU_CACHE_CLEAN); > > > + > > > bucket = get_hash_bucket(entry, &flags); > > > hash_bucket_add(bucket, entry); > > > put_hash_bucket(bucket, flags); > > > > > > - rc = active_cacheline_insert(entry); > > > + rc = active_cacheline_insert(entry, &overlap_cache_clean); > > > if (rc == -ENOMEM) { > > > pr_err_once("cacheline tracking ENOMEM, dma-debug disabled\n"); > > > global_disable = true; > > > } else if (rc == -EEXIST && > > > - !(attrs & (DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_CPU_CACHE_CLEAN)) && > > > + !(attrs & DMA_ATTR_SKIP_CPU_SYNC) && > > > + !(entry->is_cache_clean && overlap_cache_clean) && > > > !(IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) && > > > is_swiotlb_active(entry->dev))) { > > > err_printk(entry->dev, entry, >