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 84ED71A9F8B; Tue, 12 Aug 2025 16:30:17 +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=1755016217; cv=none; b=F/HVkOhvpbE/0dCyxsQISRrRWyzwVjZ0C/hEpP99EuJcny9pU5FKc+HOOF05+Iw7W9xycrH8ZBNH+Uk5AWlecQXJHOhbvajsDIjCPTazoKp9mlT6Mc53VM0oHOAmHxBCuPL2nY1JY2QACMUqALLpdltOFTz/RdrY387jBsF+8rA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755016217; c=relaxed/simple; bh=4vdLYj8onEuvH/MXXLnAQFBePXxWY8yQZFRDfo+p5Ec=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=sAfiTe6PXM9BWp2xJjZBgbCCb8y0SuiStBL/LkG+TdD9CjhEcJsQyMoYYPzYLABjhk/5aXfqIdiIxZiBA7xIdsigpprzSALtNJHOnTS/tGJ8v+aOK6xSbhvHVOLSnRdgTLpM6v3waMb5YyQVMpuHuevFyCkKlf60ob538Z1jwJQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=S/OEfawe; 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="S/OEfawe" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CC9F9C4CEF0; Tue, 12 Aug 2025 16:30:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755016217; bh=4vdLYj8onEuvH/MXXLnAQFBePXxWY8yQZFRDfo+p5Ec=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=S/OEfawesxF6JiuSKpEmq5yRCtAAgnY5wHQJGqqMuoYS7JLV20eHNHUjOKqC3+Zh4 U2mLFIn+iaIXjxxV3o6MPIN1ZVr0ph88GZ8b8E8QfdvfwyUx/j6XFagmNpL1RDNu4V GgDgmlmWp8Rp2V4uB6RjLuIV828KGm06dSKt1hRKwLoG0NBZw3EmBlmUTreD5f10sT fdZwtu4mtGbT2gZT5cjSLSHQo98pbZu4iAgfq7qR4Th001IdGotmrL89N7Zd9Ix9Rm nR45CRI7RJf0x9J4G1AzAOTRrLQVGhJZA15R/d6kKwebJeF2znCEJcAZyLvT6mKEbu p9er2rUyIl7cQ== Date: Tue, 12 Aug 2025 11:30:15 -0500 From: Bjorn Helgaas To: Keith Busch Cc: Nam Cao , Nirmal Patel , Jonathan Derrick , Lorenzo Pieralisi , Krzysztof =?utf-8?Q?Wilczy=C2=B4nski?= , Manivannan Sadhasivam , Rob Herring , Bjorn Helgaas , Thomas Gleixner , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Ammar Faizi Subject: Re: [PATCH] PCI: vmd: Remove MSI-X check on child devices Message-ID: <20250812163015.GA194338@bhelgaas> Precedence: bulk X-Mailing-List: linux-pci@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: On Tue, Aug 12, 2025 at 08:49:50AM -0600, Keith Busch wrote: > On Tue, Aug 12, 2025 at 08:27:15AM +0200, Nam Cao wrote: > > On Mon, Aug 11, 2025 at 05:46:59PM -0500, Bjorn Helgaas wrote: > > > On Mon, Aug 11, 2025 at 07:39:35AM +0200, Nam Cao wrote: > > > > Commit d7d8ab87e3e7 ("PCI: vmd: Switch to msi_create_parent_irq_domain()") > > > > added a WARN_ON sanity check that child devices support MSI-X, because VMD > > > > document says [1]: > > > > > > > > "Intel VMD only supports MSIx Interrupts from child devices and > > > > therefore the BIOS must enable PCIe Hot Plug and MSIx interrups [sic]." > > > > > > Can VMD tell the difference between an incoming MSI MWr transaction > > > and an MSI-X MWr? > > > > > > I wonder if "MSIx" was meant to mean "VMD only supports MSI or MSI-X > > > interrupts, not INTx interrupts, from child devices"? > > > > I don't know, sorry. I am hoping that the VMD maintainers can help us here. > > The doc you linked is riddled with errors. The original vmd commit > message is more accurate: VMD domains support child devices with MSI and > MSI-x interrupts. The VMD device can't even tell the difference which > one the device is using. It just manipulates messages sent to the usual > APIC address 0xfeeXXXXX. Thanks, Keith! I updated the commit log like this: d7d8ab87e3e7 ("PCI: vmd: Switch to msi_create_parent_irq_domain()") added a WARN_ON sanity check that child devices support MSI-X, because VMD document says [1]: Intel VMD only supports MSIx Interrupts from child devices and therefore the BIOS must enable PCIe Hot Plug and MSIx interrups [sic]. However, the VMD device can't even tell the difference between a child device using MSI and one using MSI-X. Per 185a383ada2e ("x86/PCI: Add driver for Intel Volume Management Device (VMD)"), VMD does not support INTx interrupts, but does support child devices using either MSI or MSI-X. Remove the sanity check to avoid the unnecessary WARN_ON reported by Ammar.