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 2F2941E506 for ; Wed, 7 Feb 2024 18:55:51 +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=1707332152; cv=none; b=VS90dwu9XQQ7MMoHTQNjg52teBKU8J+oMe0P2bj9SKLS9uLiy03aB3rnMYuQ7J57r85ofpihzQ2RFL2z7hQ95RdqZTzx70bTL1ZH6WyCQm2iql8UgfNSw4A1cdUddkPOVFK022RYGOPr9b4Ren++iX7qclr4ufMoOkhve2Vu4sU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707332152; c=relaxed/simple; bh=+ny9U/MprK9HUht7EqD3pvuq0hpKdIilxYnokCDxKjc=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=VIesaxkul81Um+hGg2PGLGh7G02SlFoCwbphqpMWuuuprX5y2dPvZSbxhFcYJAqeP7jKqm62WQy3Ca9ZGnJNe9QLVkV0u4SPupAvQAzY2LPI+1B6Srw2W7hW91VTkBBjXsaoMjWStbcZ3vMRzGvTtnbJbJsQ6uohpSKUetIYv58= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=rwfZp65n; 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="rwfZp65n" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5C670C433F1; Wed, 7 Feb 2024 18:55:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1707332151; bh=+ny9U/MprK9HUht7EqD3pvuq0hpKdIilxYnokCDxKjc=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=rwfZp65nUXTiISyDNuhpcr4/ELe5MwPy7m66vK2H57Z5LqWJci1nqsBR2Qu5lwDDg M1CTvqXQGoRL6Yzq4xfSMf9ZXgC0x/0vGlI+TTrEReXnZQ1u4kYmJsClFEzdBkC5G5 chICkTnpU30MK3Ss591wiTXxhXiQ5ALROAKqXd9WGmin/PRrhWmb2DtuLGE9Wxi3d7 yV0Nzx5kc1y2vETjYZoEuKHJgURxGAFxjbVgGM7mmGQP2TwnMB9AygiSuBufQplS6/ nKGqit8J/qs/7eJxjXPoMjc+uvJ+HOlmfNMFXXabKNasjiL1Y7EFPpuzQdmQ5Q3VAm 1QeJJH7zEQArQ== Date: Wed, 7 Feb 2024 12:55:49 -0600 From: Bjorn Helgaas To: Nirmal Patel Cc: Lorenzo Pieralisi , linux-pci@vger.kernel.org, "Rafael J. Wysocki" , Kai-Heng Feng Subject: Re: [PATCH v2] PCI: vmd: Enable Hotplug based on BIOS setting on VMD rootports Message-ID: <20240207185549.GA910460@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, Feb 06, 2024 at 05:27:29PM -0700, Nirmal Patel wrote: > ... > Did you have a chance to look at my response on January 16th to your > questions? I tried to summarize all of the potential problems and > issues with different fixes. Please let me know if it is easier if I > resend the explanation. Thanks. I did see your Jan 16 response, thanks. I had more questions after reading it, but they're more about understanding the topology seen by the host and the guest: Jan 16: https://lore.kernel.org/r/20240117004933.GA108810@bhelgaas Feb 1: https://lore.kernel.org/r/20240201211620.GA650432@bhelgaas As I mentioned in my second Feb 1 response (https://lore.kernel.org/r/20240201222245.GA650725@bhelgaas), the usual plan envisioned by the PCI Firmware spec is that an OS can use a PCIe feature if the platform has granted the OS ownership via _OSC and a device advertises the feature via a Capability in config space. My main concern with the v2 patch (https://lore.kernel.org/r/20231127211729.42668-1-nirmal.patel@linux.intel.com) is that it overrides _OSC for native_pcie_hotplug, but not for any of the other features (AER, PME, LTR, DPC, etc.) I think it's hard to read the specs and conclude that PCIe hotplug is a special case, and I think we're likely to have similar issues with other features in the future. But if you think this is the best solution, I'm OK with merging it. Bjorn