From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 136643914F6; Tue, 17 Mar 2026 21:29:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773782950; cv=none; b=HzpJ6UP/YIvPDmUj1dbbOjKZrKqSPEn7CqpwssmoUOn1OjiAf28sK4D7rDyVZOL3fyEPwRTwgWJKeVz2NoMnlnNoI3zpMTG8P6ySB7kwIhPBbATmw1To74laC9tLNoIoMCt+HQcJjLWUT3/0yJPMAk2WHPfrgWypjHB7F7wA8Mk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773782950; c=relaxed/simple; bh=EEPcdwfYA2i1wDNKfSw099Z5veH/DJsStfCV0MN+hNM=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=WsAoUbAQYy6KQn6zbIamEHg1F3c/knSqlxJilZB8sBsjoT4Zh/UuQd/43viMItNtgeKEP5p0Dg91SI+yWIjWMYkEUtqTHRCQYfwIX3XElYfArcj+eCbG1MTs5SCmPCkbfuFJsDtqQ39gzy/15aFbx0Q6tfiAL/aQRJxFscrtkpg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mNngK0/F; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mNngK0/F" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 81C6EC4CEF7; Tue, 17 Mar 2026 21:29:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773782949; bh=EEPcdwfYA2i1wDNKfSw099Z5veH/DJsStfCV0MN+hNM=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=mNngK0/Fs/0IBKQ6aMEbV8XD37uWZwqxk9Xp1x3CSxJsS/UYuc7J+7WpeXQjIv9ec X8EcEeWKHBjvgKMyu88CqnlBxL2FAWqBgqJ4ozol6/VeGTI5aw1QFR1zLgeXFDVjMj Vh6uui+Fy6IJVUmetrS8GwD0rBJEg8lPlnZn8e78rGdrnEcwsHeuy895dwjCKj/iZe dJo+fNqA/n+fe+zuUf5P+uyUVtuF5G2F5N53qMXibkbEQPNAYVaY1EcNuLb40V7IK+ bTXVtpbv+vjN6Jcthvxlff79woq7ce2WQMs/ChrloY0QQo6VedrOb7moFEJyJlBC9E IM6wbxpicP85A== Date: Tue, 17 Mar 2026 16:29:08 -0500 From: Bjorn Helgaas To: Caleb James DeLisle Cc: linux-pci@vger.kernel.org, linux-mips@vger.kernel.org, naseefkm@gmail.com, ryder.lee@mediatek.com, bhelgaas@google.com, lpieralisi@kernel.org, kwilczynski@kernel.org, mani@kernel.org, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, matthias.bgg@gmail.com, angelogioacchino.delregno@collabora.com, ansuelsmth@gmail.com, linux-mediatek@lists.infradead.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/3] PCI: Skip bridge window reads when window is not supported Message-ID: <20260317212908.GA109023@bhelgaas> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260316155157.679533-4-cjd@cjdns.fr> On Mon, Mar 16, 2026 at 03:51:57PM +0000, Caleb James DeLisle wrote: > pci_read_bridge_io() and pci_read_bridge_mmio_pref() read bridge window > registers unconditionally. If the registers are hardwired to zero > (not implemented), both base and limit will be 0. Since (0 <= 0) is > true, a bogus window [mem 0x00000000-0x000fffff] or [io 0x0000-0x0fff] > gets created. > > pci_read_bridge_windows() already detects unsupported windows by > testing register writability and sets io_window/pref_window flags > accordingly. Check these flags at the start of pci_read_bridge_io() > and pci_read_bridge_mmio_pref() to skip reading registers when the > window is not supported. The fundamental problem here is that assigned space to a bridge window that isn't implemented. I wish we understood the connection between this "read window" path and the assignment path. Maybe this patch fixes it because we enter pci_read_bridge_mmio_pref() with res->flags being NULL, and we set IORESOURCE_MEM | IORESOURCE_PREFETCH again, which makes it look like we can assign space for it? If that's the case, I think it would improve the commit log to mention the actual mechanism by which we avoid assigning space. > Suggested-by: Bjorn Helgaas > Link: https://lore.kernel.org/all/20260113210259.GA715789@bhelgaas/ > Signed-off-by: Ahmed Naseef > Signed-off-by: Caleb James DeLisle > --- > drivers/pci/probe.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index bccc7a4bdd79..4eacb741b4ec 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -395,6 +395,9 @@ static void pci_read_bridge_io(struct pci_dev *dev, struct resource *res, > unsigned long io_mask, io_granularity, base, limit; > struct pci_bus_region region; > > + if (!dev->io_window) > + return; > + > io_mask = PCI_IO_RANGE_MASK; > io_granularity = 0x1000; > if (dev->io_window_1k) { > @@ -465,6 +468,9 @@ static void pci_read_bridge_mmio_pref(struct pci_dev *dev, struct resource *res, > pci_bus_addr_t base, limit; > struct pci_bus_region region; > > + if (!dev->pref_window) > + return; > + > pci_read_config_word(dev, PCI_PREF_MEMORY_BASE, &mem_base_lo); > pci_read_config_word(dev, PCI_PREF_MEMORY_LIMIT, &mem_limit_lo); > base64 = (mem_base_lo & PCI_PREF_RANGE_MASK) << 16; > -- > 2.39.5 >